Isabelle NEWS -- history user-relevant changes

 ==============================================

 New in this Isabelle release

 ----------------------------

 *** General ***

 * Pure: considerably improved version of 'constdefs' command.  Now

   performs automatic type-inference of declared constants; additional

   support for local structure declarations (cf. locales and HOL

   records), see also isar-ref manual.  Potential INCOMPATIBILITY: need

   to observe strictly sequential dependencies of definitions within a

   single 'constdefs' section; moreover, the declared name needs to be

   an identifier.  If all fails, consider to fall back on 'consts' and

   'defs' separately.

 * Pure: improved indexed syntax and implicit structures.  First of

   all, indexed syntax provides a notational device for subscripted

   application, using the new syntax \<^bsub>term\<^esub> for arbitrary

   expressions.  Secondly, in a local context with structure

   declarations, number indexes \<^sub>n or the empty index (default

   number 1) refer to a certain fixed variable implicitly; option

   show_structs controls printing of implicit structures.  Typical

   applications of these concepts involve record types and locales.

 * Pure: clear separation of logical types and nonterminals, where the

   latter may only occur in 'syntax' specifications or type

   abbreviations.  Before that distinction was only partially

   implemented via type class "logic" vs. "{}".  Potential

   INCOMPATIBILITY in rare cases of improper use of 'types'/'consts'

   instead of 'nonterminals'/'syntax'.  Some very exotic syntax

   specifications may require further adaption (e.g. Cube/Base.thy).

 * Pure/Syntax: inner syntax includes (*(*nested*) comments*).

 * Pure/Syntax: pretty pinter now supports unbreakable blocks,

   specified in mixfix annotations as "(00...)".

 * Pure/Syntax: 'advanced' translation functions (parse_translation

   etc.) may depend on the signature of the theory context being

   presently used for parsing/printing, see also isar-ref manual.

 * Pure: tuned internal renaming of symbolic identifiers -- attach

   primes instead of base 26 numbers.

 * ML: all output via channels of writeln/warning/error etc. is now

   passed through Output.output.  This gives interface builders a

   chance to adapt text encodings in arbitrary manners (say as XML

   entities); see the hook provided by Output.add_mode.  On the other

   hand, results of Pretty.string_of/str_of (including string_of_term,

   string_of_thm etc.) are still 'raw' (containing funny \<^raw...>

   symbols), which requires separate application of Output.output

   whenever strings are *not* passed on to writeln/warning/error etc.

 *** HOL ***

 * HOL/record: reimplementation of records. Improved scalability for

   records with many fields, avoiding performance problems for type

   inference. Records are no longer composed of nested field types, but

   of nested extension types. Therefore the record type only grows

   linear in the number of extensions and not in the number of fields.

   The top-level (users) view on records is preserved.  Potential

   INCOMPATIBILITY only in strange cases, where the theory depends on

   the old record representation. The type generated for a record is

   called <record_name>_ext_type.

 * Simplifier: "record_upd_simproc" for simplification of multiple

   record updates enabled by default.  INCOMPATIBILITY: old proofs

   break occasionally, since simplification is more powerful by

   default.

 *** HOLCF ***

 * HOLCF: discontinued special version of 'constdefs' (which used to

   support continuous functions) in favor of the general Pure one with

   full type-inference.

 New in Isabelle2004 (April 2004)

 --------------------------------

 *** General ***

 * Provers/order.ML:  new efficient reasoner for partial and linear orders.

   Replaces linorder.ML.

 * Pure: Greek letters (except small lambda, \<lambda>), as well as Gothic

   (\<aa>...\<zz>\<AA>...\<ZZ>), calligraphic (\<A>...\<Z>), and Euler

   (\<a>...\<z>), are now considered normal letters, and can therefore

   be used anywhere where an ASCII letter (a...zA...Z) has until

   now. COMPATIBILITY: This obviously changes the parsing of some

   terms, especially where a symbol has been used as a binder, say

   '\<Pi>x. ...', which is now a type error since \<Pi>x will be parsed

   as an identifier.  Fix it by inserting a space around former

   symbols.  Call 'isatool fixgreek' to try to fix parsing errors in

   existing theory and ML files.

 * Pure: Macintosh and Windows line-breaks are now allowed in theory files.

 * Pure: single letter sub/superscripts (\<^isub> and \<^isup>) are now

   allowed in identifiers. Similar to Greek letters \<^isub> is now considered

   a normal (but invisible) letter. For multiple letter subscripts repeat

   \<^isub> like this: x\<^isub>1\<^isub>2.

 * Pure: There are now sub-/superscripts that can span more than one

   character. Text between \<^bsub> and \<^esub> is set in subscript in

   ProofGeneral and LaTeX, text between \<^bsup> and \<^esup> in

   superscript. The new control characters are not identifier parts.

 * Pure: Control-symbols of the form \<^raw:...> will literally print the

   content of "..." to the latex file instead of \isacntrl... . The "..."

   may consist of any printable characters excluding the end bracket >.

 * Pure: Using new Isar command "finalconsts" (or the ML functions

   Theory.add_finals or Theory.add_finals_i) it is now possible to

   declare constants "final", which prevents their being given a definition

   later.  It is useful for constants whose behaviour is fixed axiomatically

   rather than definitionally, such as the meta-logic connectives.

 * Pure: 'instance' now handles general arities with general sorts

   (i.e. intersections of classes),

 * Presentation: generated HTML now uses a CSS style sheet to make layout

   (somewhat) independent of content. It is copied from lib/html/isabelle.css.

   It can be changed to alter the colors/layout of generated pages.

 *** Isar ***

 * Tactic emulation methods rule_tac, erule_tac, drule_tac, frule_tac,

   cut_tac, subgoal_tac and thin_tac:

   - Now understand static (Isar) contexts.  As a consequence, users of Isar

     locales are no longer forced to write Isar proof scripts.

     For details see Isar Reference Manual, paragraph 4.3.2: Further tactic

     emulations.

   - INCOMPATIBILITY: names of variables to be instantiated may no

     longer be enclosed in quotes.  Instead, precede variable name with `?'.

     This is consistent with the instantiation attribute "where".

 * Attributes "where" and "of":

   - Now take type variables of instantiated theorem into account when reading

     the instantiation string.  This fixes a bug that caused instantiated

     theorems to have too special types in some circumstances.

   - "where" permits explicit instantiations of type variables.

 * Calculation commands "moreover" and "also" no longer interfere with

   current facts ("this"), admitting arbitrary combinations with "then"

   and derived forms.

 * Locales:

   - Goal statements involving the context element "includes" no longer

     generate theorems with internal delta predicates (those ending on

     "_axioms") in the premise.

     Resolve particular premise with <locale>.intro to obtain old form.

   - Fixed bug in type inference ("unify_frozen") that prevented mix of target

     specification and "includes" elements in goal statement.

   - Rule sets <locale>.intro and <locale>.axioms no longer declared as

     [intro?] and [elim?] (respectively) by default.

   - Experimental command for instantiation of locales in proof contexts:

         instantiate <label>[<attrs>]: <loc>

     Instantiates locale <loc> and adds all its theorems to the current context

     taking into account their attributes.  Label and attrs are optional

     modifiers, like in theorem declarations.  If present, names of

     instantiated theorems are qualified with <label>, and the attributes

     <attrs> are applied after any attributes these theorems might have already.

       If the locale has assumptions, a chained fact of the form

     "<loc> t1 ... tn" is expected from which instantiations of the parameters

     are derived.  The command does not support old-style locales declared

     with "locale (open)".

       A few (very simple) examples can be found in FOL/ex/LocaleInst.thy.

 * HOL: Tactic emulation methods induct_tac and case_tac understand static

   (Isar) contexts.

 *** HOL ***

 * Proof import: new image HOL4 contains the imported library from

   the HOL4 system with about 2500 theorems. It is imported by

   replaying proof terms produced by HOL4 in Isabelle. The HOL4 image

   can be used like any other Isabelle image.  See

   HOL/Import/HOL/README for more information.

 * Simplifier:

   - Much improved handling of linear and partial orders.

     Reasoners for linear and partial orders are set up for type classes

     "linorder" and "order" respectively, and are added to the default simpset

     as solvers.  This means that the simplifier can build transitivity chains

     to solve goals from the assumptions.

   - INCOMPATIBILITY: old proofs break occasionally.  Typically, applications

     of blast or auto after simplification become unnecessary because the goal

     is solved by simplification already.

 * Numerics: new theory Ring_and_Field contains over 250 basic numerical laws,

     all proved in axiomatic type classes for semirings, rings and fields.

 * Numerics:

   - Numeric types (nat, int, and in HOL-Complex rat, real, complex, etc.) are

     now formalized using the Ring_and_Field theory mentioned above.

   - INCOMPATIBILITY: simplification and arithmetic behaves somewhat differently

     than before, because now they are set up once in a generic manner.

   - INCOMPATIBILITY: many type-specific arithmetic laws have gone.

     Look for the general versions in Ring_and_Field (and Power if they concern

     exponentiation).

 * Type "rat" of the rational numbers is now available in HOL-Complex.

 * Records:

   - Record types are now by default printed with their type abbreviation

     instead of the list of all field types. This can be configured via

     the reference "print_record_type_abbr".

   - Simproc "record_upd_simproc" for simplification of multiple updates added

     (not enabled by default).

   - Simproc "record_ex_sel_eq_simproc" to simplify EX x. sel r = x resp.

     EX x. x = sel r to True (not enabled by default).

   - Tactic "record_split_simp_tac" to split and simplify records added.

 * 'specification' command added, allowing for definition by

   specification.  There is also an 'ax_specification' command that

   introduces the new constants axiomatically.

 * arith(_tac) is now able to generate counterexamples for reals as well.

 * HOL-Algebra: new locale "ring" for non-commutative rings.

 * HOL-ex: InductiveInvariant_examples illustrates advanced recursive function

   definitions, thanks to Sava Krsti\'{c} and John Matthews.

 * HOL-Matrix: a first theory for matrices in HOL with an application of

   matrix theory to linear programming.

 * Unions and Intersections:

   The x-symbol output syntax of UN and INT has been changed

   from "\<Union>x \<in> A. B" to "\<Union\<^bsub>x \<in> A\<^esub> B"

   i.e. the index formulae has become a subscript, like in normal math.

   Similarly for "\<Union>x. B", and for \<Inter> instead of \<Union>.

   The subscript version is also accepted as input syntax.

 * Unions and Intersections over Intervals:

   There is new short syntax "UN i<=n. A" for "UN i:{0..n}. A". There is

   also an x-symbol version with subscripts "\<Union>\<^bsub>i <= n\<^esub>. A"

   like in normal math, and corresponding versions for < and for intersection.

 * ML: the legacy theory structures Int and List have been removed. They had

   conflicted with ML Basis Library structures having the same names.

 * 'refute' command added to search for (finite) countermodels.  Only works

   for a fragment of HOL.  The installation of an external SAT solver is

   highly recommended.  See "HOL/Refute.thy" for details.

 * 'quickcheck' command: Allows to find counterexamples by evaluating

   formulae under an assignment of free variables to random values.

   In contrast to 'refute', it can deal with inductive datatypes,

   but cannot handle quantifiers. See "HOL/ex/Quickcheck_Examples.thy"

   for examples.

 *** HOLCF ***

 * Streams now come with concatenation and are part of the HOLCF image

 New in Isabelle2003 (May 2003)

 ------------------------------

 *** General ***

 * Provers/simplifier:

   - Completely reimplemented method simp (ML: Asm_full_simp_tac):

     Assumptions are now subject to complete mutual simplification,

     not just from left to right. The simplifier now preserves

     the order of assumptions.

     Potential INCOMPATIBILITY:

     -- simp sometimes diverges where the old version did

        not, e.g. invoking simp on the goal

         [| P (f x); y = x; f x = f y |] ==> Q

        now gives rise to the infinite reduction sequence

         P(f x) --(f x = f y)--> P(f y) --(y = x)--> P(f x) --(f x = f y)--> ...

        Using "simp (asm_lr)" (ML: Asm_lr_simp_tac) instead often solves this

        kind of problem.

     -- Tactics combining classical reasoner and simplification (such as auto)

        are also affected by this change, because many of them rely on

        simp. They may sometimes diverge as well or yield a different numbers

        of subgoals. Try to use e.g. force, fastsimp, or safe instead of auto

        in case of problems. Sometimes subsequent calls to the classical

        reasoner will fail because a preceeding call to the simplifier too

        eagerly simplified the goal, e.g. deleted redundant premises.

   - The simplifier trace now shows the names of the applied rewrite rules

   - You can limit the number of recursive invocations of the simplifier

     during conditional rewriting (where the simplifie tries to solve the

     conditions before applying the rewrite rule):

     ML "simp_depth_limit := n"

     where n is an integer. Thus you can force termination where previously

     the simplifier would diverge.

   - Accepts free variables as head terms in congruence rules.  Useful in Isar.

   - No longer aborts on failed congruence proof.  Instead, the

     congruence is ignored.

 * Pure: New generic framework for extracting programs from constructive

   proofs. See HOL/Extraction.thy for an example instantiation, as well

   as HOL/Extraction for some case studies.

 * Pure: The main goal of the proof state is no longer shown by default, only

 the subgoals. This behaviour is controlled by a new flag.

    PG menu: Isabelle/Isar -> Settings -> Show Main Goal

 (ML: Proof.show_main_goal).

 * Pure: You can find all matching introduction rules for subgoal 1, i.e. all

 rules whose conclusion matches subgoal 1:

       PG menu: Isabelle/Isar -> Show me -> matching rules

 The rules are ordered by how closely they match the subgoal.

 In particular, rules that solve a subgoal outright are displayed first

 (or rather last, the way they are printed).

 (ML: ProofGeneral.print_intros())

 * Pure: New flag trace_unify_fail causes unification to print

 diagnostic information (PG: in trace buffer) when it fails. This is

 useful for figuring out why single step proofs like rule, erule or

 assumption failed.

 * Pure: Locale specifications now produce predicate definitions

 according to the body of text (covering assumptions modulo local

 definitions); predicate "loc_axioms" covers newly introduced text,

 while "loc" is cumulative wrt. all included locale expressions; the

 latter view is presented only on export into the global theory

 context; potential INCOMPATIBILITY, use "(open)" option to fall back

 on the old view without predicates;

 * Pure: predefined locales "var" and "struct" are useful for sharing

 parameters (as in CASL, for example); just specify something like

 ``var x + var y + struct M'' as import;

 * Pure: improved thms_containing: proper indexing of facts instead of

 raw theorems; check validity of results wrt. current name space;

 include local facts of proof configuration (also covers active

 locales), cover fixed variables in index; may use "_" in term

 specification; an optional limit for the number of printed facts may

 be given (the default is 40);

 * Pure: disallow duplicate fact bindings within new-style theory files

 (batch-mode only);

 * Provers: improved induct method: assumptions introduced by case

 "foo" are split into "foo.hyps" (from the rule) and "foo.prems" (from

 the goal statement); "foo" still refers to all facts collectively;

 * Provers: the function blast.overloaded has been removed: all constants

 are regarded as potentially overloaded, which improves robustness in exchange

 for slight decrease in efficiency;

 * Provers/linorder: New generic prover for transitivity reasoning over

 linear orders.  Note: this prover is not efficient!

 * Isar: preview of problems to finish 'show' now produce an error

 rather than just a warning (in interactive mode);

 *** HOL ***

 * arith(_tac)

  - Produces a counter example if it cannot prove a goal.

    Note that the counter example may be spurious if the goal is not a formula

    of quantifier-free linear arithmetic.

    In ProofGeneral the counter example appears in the trace buffer.

  - Knows about div k and mod k where k is a numeral of type nat or int.

  - Calls full Presburger arithmetic (by Amine Chaieb) if quantifier-free

    linear arithmetic fails. This takes account of quantifiers and divisibility.

    Presburger arithmetic can also be called explicitly via presburger(_tac).

 * simp's arithmetic capabilities have been enhanced a bit: it now

 takes ~= in premises into account (by performing a case split);

 * simp reduces "m*(n div m) + n mod m" to n, even if the two summands

 are distributed over a sum of terms;

 * New tactic "trans_tac" and method "trans" instantiate

 Provers/linorder.ML for axclasses "order" and "linorder" (predicates

 "<=", "<" and "=").

 * function INCOMPATIBILITIES: Pi-sets have been redefined and moved from main

 HOL to Library/FuncSet; constant "Fun.op o" is now called "Fun.comp";

 * 'typedef' command has new option "open" to suppress the set

 definition;

 * functions Min and Max on finite sets have been introduced (theory

 Finite_Set);

 * attribute [symmetric] now works for relations as well; it turns

 (x,y) : R^-1 into (y,x) : R, and vice versa;

 * induct over a !!-quantified statement (say !!x1..xn):

   each "case" automatically performs "fix x1 .. xn" with exactly those names.

 * Map: `empty' is no longer a constant but a syntactic abbreviation for

 %x. None. Warning: empty_def now refers to the previously hidden definition

 of the empty set.

 * Algebra: formalization of classical algebra.  Intended as base for

 any algebraic development in Isabelle.  Currently covers group theory

 (up to Sylow's theorem) and ring theory (Universal Property of

 Univariate Polynomials).  Contributions welcome;

 * GroupTheory: deleted, since its material has been moved to Algebra;

 * Complex: new directory of the complex numbers with numeric constants,

 nonstandard complex numbers, and some complex analysis, standard and

 nonstandard (Jacques Fleuriot);

 * HOL-Complex: new image for analysis, replacing HOL-Real and HOL-Hyperreal;

 * Hyperreal: introduced Gauge integration and hyperreal logarithms (Jacques

 Fleuriot);

 * Real/HahnBanach: updated and adapted to locales;

 * NumberTheory: added Gauss's law of quadratic reciprocity (by Avigad,

 Gray and Kramer);

 * UNITY: added the Meier-Sanders theory of progress sets;

 * MicroJava: bytecode verifier and lightweight bytecode verifier

 as abstract algorithms, instantiated to the JVM;

 * Bali: Java source language formalization. Type system, operational

 semantics, axiomatic semantics. Supported language features:

 classes, interfaces, objects,virtual methods, static methods,

 static/instance fields, arrays, access modifiers, definite

 assignment, exceptions.

 *** ZF ***

 * ZF/Constructible: consistency proof for AC (Gödel's constructible

 universe, etc.);

 * Main ZF: virtually all theories converted to new-style format;

 *** ML ***

 * Pure: Tactic.prove provides sane interface for internal proofs;

 omits the infamous "standard" operation, so this is more appropriate

 than prove_goalw_cterm in many situations (e.g. in simprocs);

 * Pure: improved error reporting of simprocs;

 * Provers: Simplifier.simproc(_i) provides sane interface for setting

 up simprocs;

 *** Document preparation ***

 * uses \par instead of \\ for line breaks in theory text. This may

 shift some page breaks in large documents. To get the old behaviour

 use \renewcommand{\isanewline}{\mbox{}\\\mbox{}} in root.tex.

 * minimized dependencies of isabelle.sty and isabellesym.sty on

 other packages

 * \<euro> now needs package babel/greek instead of marvosym (which

 broke \Rightarrow)

 * normal size for \<zero>...\<nine> (uses \mathbf instead of

 textcomp package)

 New in Isabelle2002 (March 2002)

 --------------------------------

 *** Document preparation ***

 * greatly simplified document preparation setup, including more

 graceful interpretation of isatool usedir -i/-d/-D options, and more

 instructive isatool mkdir; users should basically be able to get

 started with "isatool mkdir HOL Test && isatool make"; alternatively,

 users may run a separate document processing stage manually like this:

 "isatool usedir -D output HOL Test && isatool document Test/output";

 * theory dependency graph may now be incorporated into documents;

 isatool usedir -g true will produce session_graph.eps/.pdf for use

 with \includegraphics of LaTeX;

 * proper spacing of consecutive markup elements, especially text

 blocks after section headings;

 * support bold style (for single symbols only), input syntax is like

 this: "\<^bold>\<alpha>" or "\<^bold>A";

 * \<bullet> is now output as bold \cdot by default, which looks much

 better in printed text;

 * added default LaTeX bindings for \<tturnstile> and \<TTurnstile>;

 note that these symbols are currently unavailable in Proof General /

 X-Symbol; new symbols \<zero>, \<one>, ..., \<nine>, and \<euro>;

 * isatool latex no longer depends on changed TEXINPUTS, instead

 isatool document copies the Isabelle style files to the target

 location;

 *** Isar ***

 * Pure/Provers: improved proof by cases and induction;

   - 'case' command admits impromptu naming of parameters (such as

     "case (Suc n)");

   - 'induct' method divinates rule instantiation from the inductive

     claim; no longer requires excessive ?P bindings for proper

     instantiation of cases;

   - 'induct' method properly enumerates all possibilities of set/type

     rules; as a consequence facts may be also passed through *type*

     rules without further ado;

   - 'induct' method now derives symbolic cases from the *rulified*

     rule (before it used to rulify cases stemming from the internal

     atomized version); this means that the context of a non-atomic

     statement becomes is included in the hypothesis, avoiding the

     slightly cumbersome show "PROP ?case" form;

   - 'induct' may now use elim-style induction rules without chaining

     facts, using ``missing'' premises from the goal state; this allows

     rules stemming from inductive sets to be applied in unstructured

     scripts, while still benefitting from proper handling of non-atomic

     statements; NB: major inductive premises need to be put first, all

     the rest of the goal is passed through the induction;

   - 'induct' proper support for mutual induction involving non-atomic

     rule statements (uses the new concept of simultaneous goals, see

     below);

   - append all possible rule selections, but only use the first

     success (no backtracking);

   - removed obsolete "(simplified)" and "(stripped)" options of methods;

   - undeclared rule case names default to numbers 1, 2, 3, ...;

   - added 'print_induct_rules' (covered by help item in recent Proof

     General versions);

   - moved induct/cases attributes to Pure, methods to Provers;

   - generic method setup instantiated for FOL and HOL;

 * Pure: support multiple simultaneous goal statements, for example

 "have a: A and b: B" (same for 'theorem' etc.); being a pure

 meta-level mechanism, this acts as if several individual goals had

 been stated separately; in particular common proof methods need to be

 repeated in order to cover all claims; note that a single elimination

 step is *not* sufficient to establish the two conjunctions, so this

 fails:

   assume "A & B" then have A and B ..   (*".." fails*)

 better use "obtain" in situations as above; alternative refer to

 multi-step methods like 'auto', 'simp_all', 'blast+' etc.;

 * Pure: proper integration with ``locales''; unlike the original

 version by Florian Kammüller, Isar locales package high-level proof

 contexts rather than raw logical ones (e.g. we admit to include

 attributes everywhere); operations on locales include merge and

 rename; support for implicit arguments (``structures''); simultaneous

 type-inference over imports and text; see also HOL/ex/Locales.thy for

 some examples;

 * Pure: the following commands have been ``localized'', supporting a

 target locale specification "(in name)": 'lemma', 'theorem',

 'corollary', 'lemmas', 'theorems', 'declare'; the results will be

 stored both within the locale and at the theory level (exported and

 qualified by the locale name);

 * Pure: theory goals may now be specified in ``long'' form, with

 ad-hoc contexts consisting of arbitrary locale elements. for example

 ``lemma foo: fixes x assumes "A x" shows "B x"'' (local syntax and

 definitions may be given, too); the result is a meta-level rule with

 the context elements being discharged in the obvious way;

 * Pure: new proof command 'using' allows to augment currently used

 facts after a goal statement ('using' is syntactically analogous to

 'apply', but acts on the goal's facts only); this allows chained facts

 to be separated into parts given before and after a claim, as in

 ``from a and b have C using d and e <proof>'';

 * Pure: renamed "antecedent" case to "rule_context";

 * Pure: new 'judgment' command records explicit information about the

 object-logic embedding (used by several tools internally); no longer

 use hard-wired "Trueprop";

 * Pure: added 'corollary' command;

 * Pure: fixed 'token_translation' command;

 * Pure: removed obsolete 'exported' attribute;

 * Pure: dummy pattern "_" in is/let is now automatically lifted over

 bound variables: "ALL x. P x --> Q x" (is "ALL x. _ --> ?C x")

 supersedes more cumbersome ... (is "ALL x. _ x --> ?C x");

 * Pure: method 'atomize' presents local goal premises as object-level

 statements (atomic meta-level propositions); setup controlled via

 rewrite rules declarations of 'atomize' attribute; example

 application: 'induct' method with proper rule statements in improper

 proof *scripts*;

 * Pure: emulation of instantiation tactics (rule_tac, cut_tac, etc.)

 now consider the syntactic context of assumptions, giving a better

 chance to get type-inference of the arguments right (this is

 especially important for locales);

 * Pure: "sorry" no longer requires quick_and_dirty in interactive

 mode;

 * Pure/obtain: the formal conclusion "thesis", being marked as

 ``internal'', may no longer be reference directly in the text;

 potential INCOMPATIBILITY, may need to use "?thesis" in rare

 situations;

 * Pure: generic 'sym' attribute which declares a rule both as pure

 'elim?' and for the 'symmetric' operation;

 * Pure: marginal comments ``--'' may now occur just anywhere in the

 text; the fixed correlation with particular command syntax has been

 discontinued;

 * Pure: new method 'rules' is particularly well-suited for proof

 search in intuitionistic logic; a bit slower than 'blast' or 'fast',

 but often produces more compact proof terms with less detours;

 * Pure/Provers/classical: simplified integration with pure rule

 attributes and methods; the classical "intro?/elim?/dest?"

 declarations coincide with the pure ones; the "rule" method no longer

 includes classically swapped intros; "intro" and "elim" methods no

 longer pick rules from the context; also got rid of ML declarations

 AddXIs/AddXEs/AddXDs; all of this has some potential for

 INCOMPATIBILITY;

 * Provers/classical: attribute 'swapped' produces classical inversions

 of introduction rules;

 * Provers/simplifier: 'simplified' attribute may refer to explicit

 rules instead of full simplifier context; 'iff' attribute handles

 conditional rules;

 * HOL: 'typedef' now allows alternative names for Rep/Abs morphisms;

 * HOL: 'recdef' now fails on unfinished automated proofs, use

 "(permissive)" option to recover old behavior;

 * HOL: 'inductive' no longer features separate (collective) attributes

 for 'intros' (was found too confusing);

 * HOL: properly declared induction rules less_induct and

 wf_induct_rule;

 *** HOL ***

 * HOL: moved over to sane numeral syntax; the new policy is as

 follows:

   - 0 and 1 are polymorphic constants, which are defined on any

   numeric type (nat, int, real etc.);

   - 2, 3, 4, ... and -1, -2, -3, ... are polymorphic numerals, based

   binary representation internally;

   - type nat has special constructor Suc, and generally prefers Suc 0

   over 1::nat and Suc (Suc 0) over 2::nat;

 This change may cause significant problems of INCOMPATIBILITY; here

 are some hints on converting existing sources:

   - due to the new "num" token, "-0" and "-1" etc. are now atomic

   entities, so expressions involving "-" (unary or binary minus) need

   to be spaced properly;

   - existing occurrences of "1" may need to be constraint "1::nat" or

   even replaced by Suc 0; similar for old "2";

   - replace "#nnn" by "nnn", and "#-nnn" by "-nnn";

   - remove all special provisions on numerals in proofs;

 * HOL: simp rules nat_number expand numerals on nat to Suc/0

 representation (depends on bin_arith_simps in the default context);

 * HOL: symbolic syntax for x^2 (numeral 2);

 * HOL: the class of all HOL types is now called "type" rather than

 "term"; INCOMPATIBILITY, need to adapt references to this type class

 in axclass/classes, instance/arities, and (usually rare) occurrences

 in typings (of consts etc.); internally the class is called

 "HOL.type", ML programs should refer to HOLogic.typeS;

 * HOL/record package improvements:

   - new derived operations "fields" to build a partial record section,

     "extend" to promote a fixed record to a record scheme, and

     "truncate" for the reverse; cf. theorems "xxx.defs", which are *not*

     declared as simp by default;

   - shared operations ("more", "fields", etc.) now need to be always

     qualified) --- potential INCOMPATIBILITY;

   - removed "make_scheme" operations (use "make" with "extend") --

     INCOMPATIBILITY;

   - removed "more" class (simply use "term") -- INCOMPATIBILITY;

   - provides cases/induct rules for use with corresponding Isar

     methods (for concrete records, record schemes, concrete more

     parts, and schematic more parts -- in that order);

   - internal definitions directly based on a light-weight abstract

     theory of product types over typedef rather than datatype;

 * HOL: generic code generator for generating executable ML code from

 specifications; specific support for HOL constructs such as inductive

 datatypes and sets, as well as recursive functions; can be invoked

 via 'generate_code' theory section;

 * HOL: canonical cases/induct rules for n-tuples (n = 3..7);

 * HOL: consolidated and renamed several theories.  In particular:

         Ord.thy has been absorbed into HOL.thy

         String.thy has been absorbed into List.thy

 * HOL: concrete setsum syntax "\<Sum>i:A. b" == "setsum (%i. b) A"

 (beware of argument permutation!);

 * HOL: linorder_less_split superseded by linorder_cases;

 * HOL/List: "nodups" renamed to "distinct";

 * HOL: added "The" definite description operator; move Hilbert's "Eps"

 to peripheral theory "Hilbert_Choice"; some INCOMPATIBILITIES:

   - Ex_def has changed, now need to use some_eq_ex

 * HOL: made split_all_tac safe; EXISTING PROOFS MAY FAIL OR LOOP, so

 in this (rare) case use:

   delSWrapper "split_all_tac"

   addSbefore ("unsafe_split_all_tac", unsafe_split_all_tac)

 * HOL: added safe wrapper "split_conv_tac" to claset; EXISTING PROOFS

 MAY FAIL;

 * HOL: introduced f^n = f o ... o f; warning: due to the limits of

 Isabelle's type classes, ^ on functions and relations has too general

 a domain, namely ('a * 'b) set and 'a => 'b; this means that it may be

 necessary to attach explicit type constraints;

 * HOL/Relation: the prefix name of the infix "O" has been changed from

 "comp" to "rel_comp"; INCOMPATIBILITY: a few theorems have been

 renamed accordingly (eg "compI" -> "rel_compI").

 * HOL: syntax translations now work properly with numerals and records

 expressions;

 * HOL: bounded abstraction now uses syntax "%" / "\<lambda>" instead

 of "lam" -- INCOMPATIBILITY;

 * HOL: got rid of some global declarations (potential INCOMPATIBILITY

 for ML tools): const "()" renamed "Product_Type.Unity", type "unit"

 renamed "Product_Type.unit";

 * HOL: renamed rtrancl_into_rtrancl2 to converse_rtrancl_into_rtrancl

 * HOL: removed obsolete theorem "optionE" (use "option.exhaust", or

 the "cases" method);

 * HOL/GroupTheory: group theory examples including Sylow's theorem (by

 Florian Kammüller);

 * HOL/IMP: updated and converted to new-style theory format; several

 parts turned into readable document, with proper Isar proof texts and

 some explanations (by Gerwin Klein);

 * HOL-Real: added Complex_Numbers (by Gertrud Bauer);

 * HOL-Hyperreal is now a logic image;

 *** HOLCF ***

 * Isar: consts/constdefs supports mixfix syntax for continuous

 operations;

 * Isar: domain package adapted to new-style theory format, e.g. see

 HOLCF/ex/Dnat.thy;

 * theory Lift: proper use of rep_datatype lift instead of ML hacks --

 potential INCOMPATIBILITY; now use plain induct_tac instead of former

 lift.induct_tac, always use UU instead of Undef;

 * HOLCF/IMP: updated and converted to new-style theory;

 *** ZF ***

 * Isar: proper integration of logic-specific tools and packages,

 including theory commands '(co)inductive', '(co)datatype',

 'rep_datatype', 'inductive_cases', as well as methods 'ind_cases',

 'induct_tac', 'case_tac', and 'typecheck' (with attribute 'TC');

 * theory Main no longer includes AC; for the Axiom of Choice, base

 your theory on Main_ZFC;

 * the integer library now covers quotients and remainders, with many

 laws relating division to addition, multiplication, etc.;

 * ZF/UNITY: Chandy and Misra's UNITY is now available in ZF, giving a

 typeless version of the formalism;

 * ZF/AC, Coind, IMP, Resid: updated and converted to new-style theory

 format;

 * ZF/Induct: new directory for examples of inductive definitions,

 including theory Multiset for multiset orderings; converted to

 new-style theory format;

 * ZF: many new theorems about lists, ordinals, etc.;

 *** General ***

 * Pure/kernel: meta-level proof terms (by Stefan Berghofer); reference

 variable proof controls level of detail: 0 = no proofs (only oracle

 dependencies), 1 = lemma dependencies, 2 = compact proof terms; see

 also ref manual for further ML interfaces;

 * Pure/axclass: removed obsolete ML interface

 goal_subclass/goal_arity;

 * Pure/syntax: new token syntax "num" for plain numerals (without "#"

 of "xnum"); potential INCOMPATIBILITY, since -0, -1 etc. are now

 separate tokens, so expressions involving minus need to be spaced

 properly;

 * Pure/syntax: support non-oriented infixes, using keyword "infix"

 rather than "infixl" or "infixr";

 * Pure/syntax: concrete syntax for dummy type variables admits genuine

 sort constraint specifications in type inference; e.g. "x::_::foo"

 ensures that the type of "x" is of sort "foo" (but not necessarily a

 type variable);

 * Pure/syntax: print modes "type_brackets" and "no_type_brackets"

 control output of nested => (types); the default behavior is

 "type_brackets";

 * Pure/syntax: builtin parse translation for "_constify" turns valued

 tokens into AST constants;

 * Pure/syntax: prefer later declarations of translations and print

 translation functions; potential INCOMPATIBILITY: need to reverse

 multiple declarations for same syntax element constant;

 * Pure/show_hyps reset by default (in accordance to existing Isar

 practice);

 * Provers/classical: renamed addaltern to addafter, addSaltern to

 addSafter;

 * Provers/clasimp: ``iff'' declarations now handle conditional rules

 as well;

 * system: tested support for MacOS X; should be able to get Isabelle +

 Proof General to work in a plain Terminal after installing Poly/ML

 (e.g. from the Isabelle distribution area) and GNU bash alone

 (e.g. from http://www.apple.com); full X11, XEmacs and X-Symbol

 support requires further installations, e.g. from

 http://fink.sourceforge.net/);

 * system: support Poly/ML 4.1.1 (able to manage larger heaps);

 * system: reduced base memory usage by Poly/ML (approx. 20 MB instead

 of 40 MB), cf. ML_OPTIONS;

 * system: Proof General keywords specification is now part of the

 Isabelle distribution (see etc/isar-keywords.el);

 * system: support for persistent Proof General sessions (refrain from

 outdating all loaded theories on startup); user may create writable

 logic images like this: ``isabelle -q HOL Test'';

 * system: smart selection of Isabelle process versus Isabelle

 interface, accommodates case-insensitive file systems (e.g. HFS+); may

 run both "isabelle" and "Isabelle" even if file names are badly

 damaged (executable inspects the case of the first letter of its own

 name); added separate "isabelle-process" and "isabelle-interface";

 * system: refrain from any attempt at filtering input streams; no

 longer support ``8bit'' encoding of old isabelle font, instead proper

 iso-latin characters may now be used; the related isatools

 "symbolinput" and "nonascii" have disappeared as well;

 * system: removed old "xterm" interface (the print modes "xterm" and

 "xterm_color" are still available for direct use in a suitable

 terminal);

 New in Isabelle99-2 (February 2001)

 -----------------------------------

 *** Overview of INCOMPATIBILITIES ***

 * HOL: please note that theories in the Library and elsewhere often use the

 new-style (Isar) format; to refer to their theorems in an ML script you must

 bind them to ML identifers by e.g.      val thm_name = thm "thm_name";

 * HOL: inductive package no longer splits induction rule aggressively,

 but only as far as specified by the introductions given; the old

 format may be recovered via ML function complete_split_rule or attribute

 'split_rule (complete)';

 * HOL: induct renamed to lfp_induct, lfp_Tarski to lfp_unfold,

 gfp_Tarski to gfp_unfold;

 * HOL: contrapos, contrapos2 renamed to contrapos_nn, contrapos_pp;

 * HOL: infix "dvd" now has priority 50 rather than 70 (because it is a

 relation); infix "^^" has been renamed "``"; infix "``" has been

 renamed "`"; "univalent" has been renamed "single_valued";

 * HOL/Real: "rinv" and "hrinv" replaced by overloaded "inverse"

 operation;

 * HOLCF: infix "`" has been renamed "$"; the symbol syntax is \<cdot>;

 * Isar: 'obtain' no longer declares "that" fact as simp/intro;

 * Isar/HOL: method 'induct' now handles non-atomic goals; as a

 consequence, it is no longer monotonic wrt. the local goal context

 (which is now passed through the inductive cases);

 * Document preparation: renamed standard symbols \<ll> to \<lless> and

 \<gg> to \<ggreater>;

 *** Document preparation ***

 * \isabellestyle{NAME} selects version of Isabelle output (currently

 available: are "it" for near math-mode best-style output, "sl" for

 slanted text style, and "tt" for plain type-writer; if no

 \isabellestyle command is given, output is according to slanted

 type-writer);

 * support sub/super scripts (for single symbols only), input syntax is

 like this: "A\<^sup>*" or "A\<^sup>\<star>";

 * some more standard symbols; see Appendix A of the system manual for

 the complete list of symbols defined in isabellesym.sty;

 * improved isabelle style files; more abstract symbol implementation

 (should now use \isamath{...} and \isatext{...} in custom symbol

 definitions);

 * antiquotation @{goals} and @{subgoals} for output of *dynamic* goals

 state; Note that presentation of goal states does not conform to

 actual human-readable proof documents.  Please do not include goal

 states into document output unless you really know what you are doing!

 * proper indentation of antiquoted output with proportional LaTeX

 fonts;

 * no_document ML operator temporarily disables LaTeX document

 generation;

 * isatool unsymbolize tunes sources for plain ASCII communication;

 *** Isar ***

 * Pure: Isar now suffers initial goal statements to contain unbound

 schematic variables (this does not conform to actual readable proof

 documents, due to unpredictable outcome and non-compositional proof

 checking); users who know what they are doing may use schematic goals

 for Prolog-style synthesis of proven results;

 * Pure: assumption method (an implicit finishing) now handles actual

 rules as well;

 * Pure: improved 'obtain' --- moved to Pure, insert "that" into

 initial goal, declare "that" only as Pure intro (only for single

 steps); the "that" rule assumption may now be involved in implicit

 finishing, thus ".." becomes a feasible for trivial obtains;

 * Pure: default proof step now includes 'intro_classes'; thus trivial

 instance proofs may be performed by "..";

 * Pure: ?thesis / ?this / "..." now work for pure meta-level

 statements as well;

 * Pure: more robust selection of calculational rules;

 * Pure: the builtin notion of 'finished' goal now includes the ==-refl

 rule (as well as the assumption rule);

 * Pure: 'thm_deps' command visualizes dependencies of theorems and

 lemmas, using the graph browser tool;

 * Pure: predict failure of "show" in interactive mode;

 * Pure: 'thms_containing' now takes actual terms as arguments;

 * HOL: improved method 'induct' --- now handles non-atomic goals

 (potential INCOMPATIBILITY); tuned error handling;

 * HOL: cases and induct rules now provide explicit hints about the

 number of facts to be consumed (0 for "type" and 1 for "set" rules);

 any remaining facts are inserted into the goal verbatim;

 * HOL: local contexts (aka cases) may now contain term bindings as

 well; the 'cases' and 'induct' methods new provide a ?case binding for

 the result to be shown in each case;

 * HOL: added 'recdef_tc' command;

 * isatool convert assists in eliminating legacy ML scripts;

 *** HOL ***

 * HOL/Library: a collection of generic theories to be used together

 with main HOL; the theory loader path already includes this directory

 by default; the following existing theories have been moved here:

 HOL/Induct/Multiset, HOL/Induct/Acc (as Accessible_Part), HOL/While

 (as While_Combinator), HOL/Lex/Prefix (as List_Prefix);

 * HOL/Unix: "Some aspects of Unix file-system security", a typical

 modelling and verification task performed in Isabelle/HOL +

 Isabelle/Isar + Isabelle document preparation (by Markus Wenzel).

 * HOL/Algebra: special summation operator SUM no longer exists, it has

 been replaced by setsum; infix 'assoc' now has priority 50 (like

 'dvd'); axiom 'one_not_zero' has been moved from axclass 'ring' to

 'domain', this makes the theory consistent with mathematical

 literature;

 * HOL basics: added overloaded operations "inverse" and "divide"

 (infix "/"), syntax for generic "abs" operation, generic summation

 operator \<Sum>;

 * HOL/typedef: simplified package, provide more useful rules (see also

 HOL/subset.thy);

 * HOL/datatype: induction rule for arbitrarily branching datatypes is

 now expressed as a proper nested rule (old-style tactic scripts may

 require atomize_strip_tac to cope with non-atomic premises);

 * HOL: renamed theory "Prod" to "Product_Type", renamed "split" rule

 to "split_conv" (old name still available for compatibility);

 * HOL: improved concrete syntax for strings (e.g. allows translation

 rules with string literals);

 * HOL-Real-Hyperreal: this extends HOL-Real with the hyperreals

  and Fleuriot's mechanization of analysis, including the transcendental

  functions for the reals;

 * HOL/Real, HOL/Hyperreal: improved arithmetic simplification;

 *** CTT ***

 * CTT: x-symbol support for Pi, Sigma, -->, : (membership); note that

 "lam" is displayed as TWO lambda-symbols

 * CTT: theory Main now available, containing everything (that is, Bool

 and Arith);

 *** General ***

 * Pure: the Simplifier has been implemented properly as a derived rule

 outside of the actual kernel (at last!); the overall performance

 penalty in practical applications is about 50%, while reliability of

 the Isabelle inference kernel has been greatly improved;

 * print modes "brackets" and "no_brackets" control output of nested =>

 (types) and ==> (props); the default behaviour is "brackets";

 * Provers: fast_tac (and friends) now handle actual object-logic rules

 as assumptions as well;

 * system: support Poly/ML 4.0;

 * system: isatool install handles KDE version 1 or 2;

 New in Isabelle99-1 (October 2000)

 ----------------------------------

 *** Overview of INCOMPATIBILITIES ***

 * HOL: simplification of natural numbers is much changed; to partly

 recover the old behaviour (e.g. to prevent n+n rewriting to #2*n)

 issue the following ML commands:

   Delsimprocs Nat_Numeral_Simprocs.cancel_numerals;

   Delsimprocs [Nat_Numeral_Simprocs.combine_numerals];

 * HOL: simplification no longer dives into case-expressions; this is

 controlled by "t.weak_case_cong" for each datatype t;

 * HOL: nat_less_induct renamed to less_induct;

 * HOL: systematic renaming of the SOME (Eps) rules, may use isatool

 fixsome to patch .thy and .ML sources automatically;

   select_equality  -> some_equality

   select_eq_Ex     -> some_eq_ex

   selectI2EX       -> someI2_ex

   selectI2         -> someI2

   selectI          -> someI

   select1_equality -> some1_equality

   Eps_sym_eq       -> some_sym_eq_trivial

   Eps_eq           -> some_eq_trivial

 * HOL: exhaust_tac on datatypes superceded by new generic case_tac;

 * HOL: removed obsolete theorem binding expand_if (refer to split_if

 instead);

 * HOL: the recursion equations generated by 'recdef' are now called

 f.simps instead of f.rules;

 * HOL: qed_spec_mp now also handles bounded ALL as well;

 * HOL: 0 is now overloaded, so the type constraint ":: nat" may

 sometimes be needed;

 * HOL: the constant for "f``x" is now "image" rather than "op ``";

 * HOL: the constant for "f-``x" is now "vimage" rather than "op -``";

 * HOL: the disjoint sum is now "<+>" instead of "Plus"; the cartesian

 product is now "<*>" instead of "Times"; the lexicographic product is

 now "<*lex*>" instead of "**";

 * HOL: theory Sexp is now in HOL/Induct examples (it used to be part

 of main HOL, but was unused); better use HOL's datatype package;

 * HOL: removed "symbols" syntax for constant "override" of theory Map;

 the old syntax may be recovered as follows:

   syntax (symbols)

     override  :: "('a ~=> 'b) => ('a ~=> 'b) => ('a ~=> 'b)"

       (infixl "\\<oplus>" 100)

 * HOL/Real: "rabs" replaced by overloaded "abs" function;

 * HOL/ML: even fewer consts are declared as global (see theories Ord,

 Lfp, Gfp, WF); this only affects ML packages that refer to const names

 internally;

 * HOL and ZF: syntax for quotienting wrt an equivalence relation

 changed from A/r to A//r;

 * ZF: new treatment of arithmetic (nat & int) may break some old

 proofs;

 * Isar: renamed some attributes (RS -> THEN, simplify -> simplified,

 rulify -> rule_format, elimify -> elim_format, ...);

 * Isar/Provers: intro/elim/dest attributes changed; renamed

 intro/intro!/intro!! flags to intro!/intro/intro? (in most cases, one

 should have to change intro!! to intro? only); replaced "delrule" by

 "rule del";

 * Isar/HOL: renamed "intrs" to "intros" in inductive definitions;

 * Provers: strengthened force_tac by using new first_best_tac;

 * LaTeX document preparation: several changes of isabelle.sty (see

 lib/texinputs);

 *** Document preparation ***

 * formal comments (text blocks etc.) in new-style theories may now

 contain antiquotations of thm/prop/term/typ/text to be presented

 according to latex print mode; concrete syntax is like this:

 @{term[show_types] "f(x) = a + x"};

 * isatool mkdir provides easy setup of Isabelle session directories,

 including proper document sources;

 * generated LaTeX sources are now deleted after successful run

 (isatool document -c); may retain a copy somewhere else via -D option

 of isatool usedir;

 * isatool usedir -D now lets isatool latex -o sty update the Isabelle

 style files, achieving self-contained LaTeX sources and simplifying

 LaTeX debugging;

 * old-style theories now produce (crude) LaTeX output as well;

 * browser info session directories are now self-contained (may be put

 on WWW server seperately); improved graphs of nested sessions; removed

 graph for 'all sessions';

 * several improvements in isabelle style files; \isabellestyle{it}

 produces fake math mode output; \isamarkupheader is now \section by

 default; see lib/texinputs/isabelle.sty etc.;

 *** Isar ***

 * Isar/Pure: local results and corresponding term bindings are now

 subject to Hindley-Milner polymorphism (similar to ML); this

 accommodates incremental type-inference very nicely;

 * Isar/Pure: new derived language element 'obtain' supports

 generalized existence reasoning;

 * Isar/Pure: new calculational elements 'moreover' and 'ultimately'

 support accumulation of results, without applying any rules yet;

 useful to collect intermediate results without explicit name

 references, and for use with transitivity rules with more than 2

 premises;

 * Isar/Pure: scalable support for case-analysis type proofs: new

 'case' language element refers to local contexts symbolically, as

 produced by certain proof methods; internally, case names are attached

 to theorems as "tags";

 * Isar/Pure: theory command 'hide' removes declarations from

 class/type/const name spaces;

 * Isar/Pure: theory command 'defs' supports option "(overloaded)" to

 indicate potential overloading;

 * Isar/Pure: changed syntax of local blocks from {{ }} to { };

 * Isar/Pure: syntax of sorts made 'inner', i.e. have to write

 "{a,b,c}" instead of {a,b,c};

 * Isar/Pure now provides its own version of intro/elim/dest

 attributes; useful for building new logics, but beware of confusion

 with the version in Provers/classical;

 * Isar/Pure: the local context of (non-atomic) goals is provided via

 case name 'antecedent';

 * Isar/Pure: removed obsolete 'transfer' attribute (transfer of thms

 to the current context is now done automatically);

 * Isar/Pure: theory command 'method_setup' provides a simple interface

 for definining proof methods in ML;

 * Isar/Provers: intro/elim/dest attributes changed; renamed

 intro/intro!/intro!! flags to intro!/intro/intro? (INCOMPATIBILITY, in

 most cases, one should have to change intro!! to intro? only);

 replaced "delrule" by "rule del";

 * Isar/Provers: new 'hypsubst' method, plain 'subst' method and

 'symmetric' attribute (the latter supercedes [RS sym]);

 * Isar/Provers: splitter support (via 'split' attribute and 'simp'

 method modifier); 'simp' method: 'only:' modifier removes loopers as

 well (including splits);

 * Isar/Provers: Simplifier and Classical methods now support all kind

 of modifiers used in the past, including 'cong', 'iff', etc.

 * Isar/Provers: added 'fastsimp' and 'clarsimp' methods (combination

 of Simplifier and Classical reasoner);

 * Isar/HOL: new proof method 'cases' and improved version of 'induct'

 now support named cases; major packages (inductive, datatype, primrec,

 recdef) support case names and properly name parameters;

 * Isar/HOL: new transitivity rules for substitution in inequalities --

 monotonicity conditions are extracted to be proven at end of

 calculations;

 * Isar/HOL: removed 'case_split' thm binding, should use 'cases' proof

 method anyway;

 * Isar/HOL: removed old expand_if = split_if; theorems if_splits =

 split_if split_if_asm; datatype package provides theorems foo.splits =

 foo.split foo.split_asm for each datatype;

 * Isar/HOL: tuned inductive package, rename "intrs" to "intros"

 (potential INCOMPATIBILITY), emulation of mk_cases feature for proof

 scripts: new 'inductive_cases' command and 'ind_cases' method; (Note:

 use "(cases (simplified))" method in proper proof texts);

 * Isar/HOL: added global 'arith_split' attribute for 'arith' method;

 * Isar: names of theorems etc. may be natural numbers as well;

 * Isar: 'pr' command: optional arguments for goals_limit and

 ProofContext.prems_limit; no longer prints theory contexts, but only

 proof states;

 * Isar: diagnostic commands 'pr', 'thm', 'prop', 'term', 'typ' admit

 additional print modes to be specified; e.g. "pr(latex)" will print

 proof state according to the Isabelle LaTeX style;

 * Isar: improved support for emulating tactic scripts, including proof

 methods 'rule_tac' etc., 'cut_tac', 'thin_tac', 'subgoal_tac',

 'rename_tac', 'rotate_tac', 'tactic', and 'case_tac' / 'induct_tac'

 (for HOL datatypes);

 * Isar: simplified (more robust) goal selection of proof methods: 1st

 goal, all goals, or explicit goal specifier (tactic emulation); thus

 'proof method scripts' have to be in depth-first order;

 * Isar: tuned 'let' syntax: replaced 'as' keyword by 'and';

 * Isar: removed 'help' command, which hasn't been too helpful anyway;

 should instead use individual commands for printing items

 (print_commands, print_methods etc.);

 * Isar: added 'nothing' --- the empty list of theorems;

 *** HOL ***

 * HOL/MicroJava: formalization of a fragment of Java, together with a

 corresponding virtual machine and a specification of its bytecode

 verifier and a lightweight bytecode verifier, including proofs of

 type-safety; by Gerwin Klein, Tobias Nipkow, David von Oheimb, and

 Cornelia Pusch (see also the homepage of project Bali at

 http://isabelle.in.tum.de/Bali/);

 * HOL/Algebra: new theory of rings and univariate polynomials, by

 Clemens Ballarin;

 * HOL/NumberTheory: fundamental Theorem of Arithmetic, Chinese

 Remainder Theorem, Fermat/Euler Theorem, Wilson's Theorem, by Thomas M

 Rasmussen;

 * HOL/Lattice: fundamental concepts of lattice theory and order

 structures, including duals, properties of bounds versus algebraic

 laws, lattice operations versus set-theoretic ones, the Knaster-Tarski

 Theorem for complete lattices etc.; may also serve as a demonstration

 for abstract algebraic reasoning using axiomatic type classes, and

 mathematics-style proof in Isabelle/Isar; by Markus Wenzel;

 * HOL/Prolog: a (bare-bones) implementation of Lambda-Prolog, by David

 von Oheimb;

 * HOL/IMPP: extension of IMP with local variables and mutually

 recursive procedures, by David von Oheimb;

 * HOL/Lambda: converted into new-style theory and document;

 * HOL/ex/Multiquote: example of multiple nested quotations and

 anti-quotations -- basically a generalized version of de-Bruijn

 representation; very useful in avoiding lifting of operations;

 * HOL/record: added general record equality rule to simpset; fixed

 select-update simplification procedure to handle extended records as

 well; admit "r" as field name;

 * HOL: 0 is now overloaded over the new sort "zero", allowing its use with

 other numeric types and also as the identity of groups, rings, etc.;

 * HOL: new axclass plus_ac0 for addition with the AC-laws and 0 as identity.

 Types nat and int belong to this axclass;

 * HOL: greatly improved simplification involving numerals of type nat, int, real:

    (i + #8 + j) = Suc k simplifies to  #7 + (i + j) = k

    i*j + k + j*#3*i     simplifies to  #4*(i*j) + k

   two terms #m*u and #n*u are replaced by #(m+n)*u

     (where #m, #n and u can implicitly be 1; this is simproc combine_numerals)

   and the term/formula #m*u+x ~~ #n*u+y simplifies simplifies to #(m-n)+x ~~ y

     or x ~~ #(n-m)+y, where ~~ is one of = < <= or - (simproc cancel_numerals);

 * HOL: meson_tac is available (previously in ex/meson.ML); it is a

 powerful prover for predicate logic but knows nothing of clasets; see

 ex/mesontest.ML and ex/mesontest2.ML for example applications;

 * HOL: new version of "case_tac" subsumes both boolean case split and

 "exhaust_tac" on datatypes; INCOMPATIBILITY: exhaust_tac no longer

 exists, may define val exhaust_tac = case_tac for ad-hoc portability;

 * HOL: simplification no longer dives into case-expressions: only the

 selector expression is simplified, but not the remaining arms; to

 enable full simplification of case-expressions for datatype t, you may

 remove t.weak_case_cong from the simpset, either globally (Delcongs

 [thm"t.weak_case_cong"];) or locally (delcongs [...]).

 * HOL/recdef: the recursion equations generated by 'recdef' for

 function 'f' are now called f.simps instead of f.rules; if all

 termination conditions are proved automatically, these simplification

 rules are added to the simpset, as in primrec; rules may be named

 individually as well, resulting in a separate list of theorems for

 each equation;

 * HOL/While is a new theory that provides a while-combinator. It

 permits the definition of tail-recursive functions without the

 provision of a termination measure. The latter is necessary once the

 invariant proof rule for while is applied.

 * HOL: new (overloaded) notation for the set of elements below/above

 some element: {..u}, {..u(}, {l..}, {)l..}. See theory SetInterval.

 * HOL: theorems impI, allI, ballI bound as "strip";

 * HOL: new tactic induct_thm_tac: thm -> string -> int -> tactic

 induct_tac th "x1 ... xn" expects th to have a conclusion of the form

 P v1 ... vn and abbreviates res_inst_tac [("v1","x1"),...,("vn","xn")] th;

 * HOL/Real: "rabs" replaced by overloaded "abs" function;

 * HOL: theory Sexp now in HOL/Induct examples (it used to be part of

 main HOL, but was unused);

 * HOL: fewer consts declared as global (e.g. have to refer to

 "Lfp.lfp" instead of "lfp" internally; affects ML packages only);

 * HOL: tuned AST representation of nested pairs, avoiding bogus output

 in case of overlap with user translations (e.g. judgements over

 tuples); (note that the underlying logical represenation is still

 bogus);

 *** ZF ***

 * ZF: simplification automatically cancels common terms in arithmetic

 expressions over nat and int;

 * ZF: new treatment of nat to minimize type-checking: all operators

 coerce their operands to a natural number using the function natify,

 making the algebraic laws unconditional;

 * ZF: as above, for int: operators coerce their operands to an integer

 using the function intify;

 * ZF: the integer library now contains many of the usual laws for the

 orderings, including $<=, and monotonicity laws for $+ and $*;

 * ZF: new example ZF/ex/NatSum to demonstrate integer arithmetic

 simplification;

 * FOL and ZF: AddIffs now available, giving theorems of the form P<->Q

 to the simplifier and classical reasoner simultaneously;

 *** General ***

 * Provers: blast_tac now handles actual object-logic rules as

 assumptions; note that auto_tac uses blast_tac internally as well;

 * Provers: new functions rulify/rulify_no_asm: thm -> thm for turning

 outer -->/All/Ball into ==>/!!; qed_spec_mp now uses rulify_no_asm;

 * Provers: delrules now handles destruct rules as well (no longer need

 explicit make_elim);

 * Provers: Blast_tac now warns of and ignores "weak elimination rules" e.g.

   [| inj ?f;          ?f ?x = ?f ?y; ?x = ?y ==> ?W |] ==> ?W

 use instead the strong form,

   [| inj ?f; ~ ?W ==> ?f ?x = ?f ?y; ?x = ?y ==> ?W |] ==> ?W

 in HOL, FOL and ZF the function cla_make_elim will create such rules

 from destruct-rules;

 * Provers: Simplifier.easy_setup provides a fast path to basic

 Simplifier setup for new object-logics;

 * Pure: AST translation rules no longer require constant head on LHS;

 * Pure: improved name spaces: ambiguous output is qualified; support

 for hiding of names;

 * system: smart setup of canonical ML_HOME, ISABELLE_INTERFACE, and

 XSYMBOL_HOME; no longer need to do manual configuration in most

 situations;

 * system: compression of ML heaps images may now be controlled via -c

 option of isabelle and isatool usedir (currently only observed by

 Poly/ML);

 * system: isatool installfonts may handle X-Symbol fonts as well (very

 useful for remote X11);

 * system: provide TAGS file for Isabelle sources;

 * ML: infix 'OF' is a version of 'MRS' with more appropriate argument

 order;

 * ML: renamed flags Syntax.trace_norm_ast to Syntax.trace_ast; global

 timing flag supersedes proof_timing and Toplevel.trace;

 * ML: new combinators |>> and |>>> for incremental transformations

 with secondary results (e.g. certain theory extensions):

 * ML: PureThy.add_defs gets additional argument to indicate potential

 overloading (usually false);

 * ML: PureThy.add_thms/add_axioms/add_defs now return theorems as

 results;

 New in Isabelle99 (October 1999)

 --------------------------------

 *** Overview of INCOMPATIBILITIES (see below for more details) ***

 * HOL: The THEN and ELSE parts of conditional expressions (if P then x else y)

 are no longer simplified.  (This allows the simplifier to unfold recursive

 functional programs.)  To restore the old behaviour, declare

     Delcongs [if_weak_cong];

 * HOL: Removed the obsolete syntax "Compl A"; use -A for set

 complement;

 * HOL: the predicate "inj" is now defined by translation to "inj_on";

 * HOL/datatype: mutual_induct_tac no longer exists --

   use induct_tac "x_1 ... x_n" instead of mutual_induct_tac ["x_1", ..., "x_n"]

 * HOL/typedef: fixed type inference for representing set; type

 arguments now have to occur explicitly on the rhs as type constraints;

 * ZF: The con_defs part of an inductive definition may no longer refer

 to constants declared in the same theory;

 * HOL, ZF: the function mk_cases, generated by the inductive

 definition package, has lost an argument.  To simplify its result, it

 uses the default simpset instead of a supplied list of theorems.

 * HOL/List: the constructors of type list are now Nil and Cons;

 * Simplifier: the type of the infix ML functions

         setSSolver addSSolver setSolver addSolver

 is now  simpset * solver -> simpset  where `solver' is a new abstract type

 for packaging solvers. A solver is created via

         mk_solver: string -> (thm list -> int -> tactic) -> solver

 where the string argument is only a comment.

 *** Proof tools ***

 * Provers/Arith/fast_lin_arith.ML contains a functor for creating a

 decision procedure for linear arithmetic. Currently it is used for

 types `nat', `int', and `real' in HOL (see below); it can, should and

 will be instantiated for other types and logics as well.

 * The simplifier now accepts rewrite rules with flexible heads, eg

      hom ?f ==> ?f(?x+?y) = ?f ?x + ?f ?y

   They are applied like any rule with a non-pattern lhs, i.e. by first-order

   matching.

 *** General ***

 * New Isabelle/Isar subsystem provides an alternative to traditional

 tactical theorem proving; together with the ProofGeneral/isar user

 interface it offers an interactive environment for developing human

 readable proof documents (Isar == Intelligible semi-automated

 reasoning); for further information see isatool doc isar-ref,

 src/HOL/Isar_examples and http://isabelle.in.tum.de/Isar/

 * improved and simplified presentation of theories: better HTML markup

 (including colors), graph views in several sizes; isatool usedir now

 provides a proper interface for user theories (via -P option); actual

 document preparation based on (PDF)LaTeX is available as well (for

 new-style theories only); see isatool doc system for more information;

 * native support for Proof General, both for classic Isabelle and

 Isabelle/Isar;

 * ML function thm_deps visualizes dependencies of theorems and lemmas,

 using the graph browser tool;

 * Isabelle manuals now also available as PDF;

 * theory loader rewritten from scratch (may not be fully

 bug-compatible); old loadpath variable has been replaced by show_path,

 add_path, del_path, reset_path functions; new operations such as

 update_thy, touch_thy, remove_thy, use/update_thy_only (see also

 isatool doc ref);

 * improved isatool install: option -k creates KDE application icon,

 option -p DIR installs standalone binaries;

 * added ML_PLATFORM setting (useful for cross-platform installations);

 more robust handling of platform specific ML images for SML/NJ;

 * the settings environment is now statically scoped, i.e. it is never

 created again in sub-processes invoked from isabelle, isatool, or

 Isabelle;

 * path element specification '~~' refers to '$ISABELLE_HOME';

 * in locales, the "assumes" and "defines" parts may be omitted if

 empty;

 * new print_mode "xsymbols" for extended symbol support (e.g. genuine

 long arrows);

 * new print_mode "HTML";

 * new flag show_tags controls display of tags of theorems (which are

 basically just comments that may be attached by some tools);

 * Isamode 2.6 requires patch to accomodate change of Isabelle font

 mode and goal output format:

 diff -r Isamode-2.6/elisp/isa-load.el Isamode/elisp/isa-load.el

 244c244

 <       (list (isa-getenv "ISABELLE") "-msymbols" logic-name)

 ---

 >       (list (isa-getenv "ISABELLE") "-misabelle_font" "-msymbols" logic-name)

 diff -r Isabelle-2.6/elisp/isa-proofstate.el Isamode/elisp/isa-proofstate.el

 181c181

 < (defconst proofstate-proofstart-regexp "^Level [0-9]+$"

 ---

 > (defconst proofstate-proofstart-regexp "^Level [0-9]+"

 * function bind_thms stores lists of theorems (cf. bind_thm);

 * new shorthand tactics ftac, eatac, datac, fatac;

 * qed (and friends) now accept "" as result name; in that case the

 theorem is not stored, but proper checks and presentation of the

 result still apply;

 * theorem database now also indexes constants "Trueprop", "all",

 "==>", "=="; thus thms_containing, findI etc. may retrieve more rules;

 *** HOL ***

 ** HOL arithmetic **

 * There are now decision procedures for linear arithmetic over nat and

 int:

 1. arith_tac copes with arbitrary formulae involving `=', `<', `<=',

 `+', `-', `Suc', `min', `max' and numerical constants; other subterms

 are treated as atomic; subformulae not involving type `nat' or `int'

 are ignored; quantified subformulae are ignored unless they are

 positive universal or negative existential. The tactic has to be

 invoked by hand and can be a little bit slow. In particular, the

 running time is exponential in the number of occurrences of `min' and

 `max', and `-' on `nat'.

 2. fast_arith_tac is a cut-down version of arith_tac: it only takes

 (negated) (in)equalities among the premises and the conclusion into

 account (i.e. no compound formulae) and does not know about `min' and

 `max', and `-' on `nat'. It is fast and is used automatically by the

 simplifier.

 NB: At the moment, these decision procedures do not cope with mixed

 nat/int formulae where the two parts interact, such as `m < n ==>

 int(m) < int(n)'.

 * HOL/Numeral provides a generic theory of numerals (encoded

 efficiently as bit strings); setup for types nat/int/real is in place;

 INCOMPATIBILITY: since numeral syntax is now polymorphic, rather than

 int, existing theories and proof scripts may require a few additional

 type constraints;

 * integer division and remainder can now be performed on constant

 arguments;

 * many properties of integer multiplication, division and remainder

 are now available;

 * An interface to the Stanford Validity Checker (SVC) is available through the

 tactic svc_tac.  Propositional tautologies and theorems of linear arithmetic

 are proved automatically.  SVC must be installed separately, and its results

 must be TAKEN ON TRUST (Isabelle does not check the proofs, but tags any

 invocation of the underlying oracle).  For SVC see

   http://verify.stanford.edu/SVC

 * IsaMakefile: the HOL-Real target now builds an actual image;

 ** HOL misc **

 * HOL/Real/HahnBanach: the Hahn-Banach theorem for real vector spaces

 (in Isabelle/Isar) -- by Gertrud Bauer;

 * HOL/BCV: generic model of bytecode verification, i.e. data-flow

 analysis for assembly languages with subtypes;

 * HOL/TLA (Lamport's Temporal Logic of Actions): major reorganization

 -- avoids syntactic ambiguities and treats state, transition, and

 temporal levels more uniformly; introduces INCOMPATIBILITIES due to

 changed syntax and (many) tactics;

 * HOL/inductive: Now also handles more general introduction rules such

   as "ALL y. (y, x) : r --> y : acc r ==> x : acc r"; monotonicity

   theorems are now maintained within the theory (maintained via the

   "mono" attribute);

 * HOL/datatype: Now also handles arbitrarily branching datatypes

   (using function types) such as

   datatype 'a tree = Atom 'a | Branch "nat => 'a tree"

 * HOL/record: record_simproc (part of the default simpset) takes care

 of selectors applied to updated records; record_split_tac is no longer

 part of the default claset; update_defs may now be removed from the

 simpset in many cases; COMPATIBILITY: old behavior achieved by

   claset_ref () := claset() addSWrapper record_split_wrapper;

   Delsimprocs [record_simproc]

 * HOL/typedef: fixed type inference for representing set; type

 arguments now have to occur explicitly on the rhs as type constraints;

 * HOL/recdef (TFL): 'congs' syntax now expects comma separated list of theorem

 names rather than an ML expression;

 * HOL/defer_recdef (TFL): like recdef but the well-founded relation can be

 supplied later.  Program schemes can be defined, such as

     "While B C s = (if B s then While B C (C s) else s)"

 where the well-founded relation can be chosen after B and C have been given.

 * HOL/List: the constructors of type list are now Nil and Cons;

 INCOMPATIBILITY: while [] and infix # syntax is still there, of

 course, ML tools referring to List.list.op # etc. have to be adapted;

 * HOL_quantifiers flag superseded by "HOL" print mode, which is

 disabled by default; run isabelle with option -m HOL to get back to

 the original Gordon/HOL-style output;

 * HOL/Ord.thy: new bounded quantifier syntax (input only): ALL x<y. P,

 ALL x<=y. P, EX x<y. P, EX x<=y. P;

 * HOL basic syntax simplified (more orthogonal): all variants of

 All/Ex now support plain / symbolic / HOL notation; plain syntax for

 Eps operator is provided as well: "SOME x. P[x]";

 * HOL/Sum.thy: sum_case has been moved to HOL/Datatype;

 * HOL/Univ.thy: infix syntax <*>, <+>, <**>, <+> eliminated and made

 thus available for user theories;

 * HOLCF/IOA/Sequents: renamed 'Cons' to 'Consq' to avoid clash with

 HOL/List; hardly an INCOMPATIBILITY since '>>' syntax is used all the

 time;

 * HOL: new tactic smp_tac: int -> int -> tactic, which applies spec

 several times and then mp;

 *** LK ***

 * the notation <<...>> is now available as a notation for sequences of

 formulas;

 * the simplifier is now installed

 * the axiom system has been generalized (thanks to Soren Heilmann)

 * the classical reasoner now has a default rule database

 *** ZF ***

 * new primrec section allows primitive recursive functions to be given

 directly (as in HOL) over datatypes and the natural numbers;

 * new tactics induct_tac and exhaust_tac for induction (or case

 analysis) over datatypes and the natural numbers;

 * the datatype declaration of type T now defines the recursor T_rec;

 * simplification automatically does freeness reasoning for datatype

 constructors;

 * automatic type-inference, with AddTCs command to insert new

 type-checking rules;

 * datatype introduction rules are now added as Safe Introduction rules

 to the claset;

 * the syntax "if P then x else y" is now available in addition to

 if(P,x,y);

 *** Internal programming interfaces ***

 * tuned simplifier trace output; new flag debug_simp;

 * structures Vartab / Termtab (instances of TableFun) offer efficient

 tables indexed by indexname_ord / term_ord (compatible with aconv);

 * AxClass.axclass_tac lost the theory argument;

 * tuned current_goals_markers semantics: begin / end goal avoids

 printing empty lines;

 * removed prs and prs_fn hook, which was broken because it did not

 include \n in its semantics, forcing writeln to add one

 uncoditionally; replaced prs_fn by writeln_fn; consider std_output:

 string -> unit if you really want to output text without newline;

 * Symbol.output subject to print mode; INCOMPATIBILITY: defaults to

 plain output, interface builders may have to enable 'isabelle_font'

 mode to get Isabelle font glyphs as before;

 * refined token_translation interface; INCOMPATIBILITY: output length

 now of type real instead of int;

 * theory loader actions may be traced via new ThyInfo.add_hook

 interface (see src/Pure/Thy/thy_info.ML); example application: keep

 your own database of information attached to *whole* theories -- as

 opposed to intra-theory data slots offered via TheoryDataFun;

 * proper handling of dangling sort hypotheses (at last!);

 Thm.strip_shyps and Drule.strip_shyps_warning take care of removing

 extra sort hypotheses that can be witnessed from the type signature;

 the force_strip_shyps flag is gone, any remaining shyps are simply

 left in the theorem (with a warning issued by strip_shyps_warning);

 New in Isabelle98-1 (October 1998)

 ----------------------------------

 *** Overview of INCOMPATIBILITIES (see below for more details) ***

 * several changes of automated proof tools;

 * HOL: major changes to the inductive and datatype packages, including

 some minor incompatibilities of theory syntax;

 * HOL: renamed r^-1 to 'converse' from 'inverse'; 'inj_onto' is now

 called `inj_on';

 * HOL: removed duplicate thms in Arith:

   less_imp_add_less  should be replaced by  trans_less_add1

   le_imp_add_le      should be replaced by  trans_le_add1

 * HOL: unary minus is now overloaded (new type constraints may be

 required);

 * HOL and ZF: unary minus for integers is now #- instead of #~.  In

 ZF, expressions such as n#-1 must be changed to n#- 1, since #-1 is

 now taken as an integer constant.

 * Pure: ML function 'theory_of' renamed to 'theory';

 *** Proof tools ***

 * Simplifier:

   1. Asm_full_simp_tac is now more aggressive.

      1. It will sometimes reorient premises if that increases their power to

         simplify.

      2. It does no longer proceed strictly from left to right but may also

         rotate premises to achieve further simplification.

      For compatibility reasons there is now Asm_lr_simp_tac which is like the

      old Asm_full_simp_tac in that it does not rotate premises.

   2. The simplifier now knows a little bit about nat-arithmetic.

 * Classical reasoner: wrapper mechanism for the classical reasoner now

 allows for selected deletion of wrappers, by introduction of names for

 wrapper functionals.  This implies that addbefore, addSbefore,

 addaltern, and addSaltern now take a pair (name, tactic) as argument,

 and that adding two tactics with the same name overwrites the first

 one (emitting a warning).

   type wrapper = (int -> tactic) -> (int -> tactic)

   setWrapper, setSWrapper, compWrapper and compSWrapper are replaced by

   addWrapper, addSWrapper: claset * (string * wrapper) -> claset

   delWrapper, delSWrapper: claset *  string            -> claset

   getWrapper is renamed to appWrappers, getSWrapper to appSWrappers;

 * Classical reasoner: addbefore/addSbefore now have APPEND/ORELSE

 semantics; addbefore now affects only the unsafe part of step_tac

 etc.; this affects addss/auto_tac/force_tac, so EXISTING PROOFS MAY

 FAIL, but proofs should be fixable easily, e.g. by replacing Auto_tac

 by Force_tac;

 * Classical reasoner: setwrapper to setWrapper and compwrapper to

 compWrapper; added safe wrapper (and access functions for it);

 * HOL/split_all_tac is now much faster and fails if there is nothing

 to split.  Some EXISTING PROOFS MAY REQUIRE ADAPTION because the order

 and the names of the automatically generated variables have changed.

 split_all_tac has moved within claset() from unsafe wrappers to safe

 wrappers, which means that !!-bound variables are split much more

 aggressively, and safe_tac and clarify_tac now split such variables.

 If this splitting is not appropriate, use delSWrapper "split_all_tac".

 Note: the same holds for record_split_tac, which does the job of

 split_all_tac for record fields.

 * HOL/Simplifier: Rewrite rules for case distinctions can now be added

 permanently to the default simpset using Addsplits just like

 Addsimps. They can be removed via Delsplits just like

 Delsimps. Lower-case versions are also available.

 * HOL/Simplifier: The rule split_if is now part of the default

 simpset. This means that the simplifier will eliminate all occurrences

 of if-then-else in the conclusion of a goal. To prevent this, you can

 either remove split_if completely from the default simpset by

 `Delsplits [split_if]' or remove it in a specific call of the

 simplifier using `... delsplits [split_if]'.  You can also add/delete

 other case splitting rules to/from the default simpset: every datatype

 generates suitable rules `split_t_case' and `split_t_case_asm' (where

 t is the name of the datatype).

 * Classical reasoner / Simplifier combination: new force_tac (and

 derivatives Force_tac, force) combines rewriting and classical

 reasoning (and whatever other tools) similarly to auto_tac, but is

 aimed to solve the given subgoal completely.

 *** General ***

 * new top-level commands `Goal' and `Goalw' that improve upon `goal'

 and `goalw': the theory is no longer needed as an explicit argument -

 the current theory context is used; assumptions are no longer returned

 at the ML-level unless one of them starts with ==> or !!; it is

 recommended to convert to these new commands using isatool fixgoal

 (backup your sources first!);

 * new top-level commands 'thm' and 'thms' for retrieving theorems from

 the current theory context, and 'theory' to lookup stored theories;

 * new theory section 'locale' for declaring constants, assumptions and

 definitions that have local scope;

 * new theory section 'nonterminals' for purely syntactic types;

 * new theory section 'setup' for generic ML setup functions

 (e.g. package initialization);

 * the distribution now includes Isabelle icons: see

 lib/logo/isabelle-{small,tiny}.xpm;

 * isatool install - install binaries with absolute references to

 ISABELLE_HOME/bin;

 * isatool logo -- create instances of the Isabelle logo (as EPS);

 * print mode 'emacs' reserved for Isamode;

 * support multiple print (ast) translations per constant name;

 * theorems involving oracles are now printed with a suffixed [!];

 *** HOL ***

 * there is now a tutorial on Isabelle/HOL (do 'isatool doc tutorial');

 * HOL/inductive package reorganized and improved: now supports mutual

 definitions such as

   inductive EVEN ODD

     intrs

       null "0 : EVEN"

       oddI "n : EVEN ==> Suc n : ODD"

       evenI "n : ODD ==> Suc n : EVEN"

 new theorem list "elims" contains an elimination rule for each of the

 recursive sets; inductive definitions now handle disjunctive premises

 correctly (also ZF);

 INCOMPATIBILITIES: requires Inductive as an ancestor; component

 "mutual_induct" no longer exists - the induction rule is always

 contained in "induct";

 * HOL/datatype package re-implemented and greatly improved: now

 supports mutually recursive datatypes such as

   datatype

     'a aexp = IF_THEN_ELSE ('a bexp) ('a aexp) ('a aexp)

             | SUM ('a aexp) ('a aexp)

             | DIFF ('a aexp) ('a aexp)

             | NUM 'a

   and

     'a bexp = LESS ('a aexp) ('a aexp)

             | AND ('a bexp) ('a bexp)

             | OR ('a bexp) ('a bexp)

 as well as indirectly recursive datatypes such as

   datatype

     ('a, 'b) term = Var 'a

                   | App 'b ((('a, 'b) term) list)

 The new tactic  mutual_induct_tac [<var_1>, ..., <var_n>] i  performs

 induction on mutually / indirectly recursive datatypes.

 Primrec equations are now stored in theory and can be accessed via

 <function_name>.simps.

 INCOMPATIBILITIES:

   - Theories using datatypes must now have theory Datatype as an

     ancestor.

   - The specific <typename>.induct_tac no longer exists - use the

     generic induct_tac instead.

   - natE has been renamed to nat.exhaust - use exhaust_tac

     instead of res_inst_tac ... natE. Note that the variable

     names in nat.exhaust differ from the names in natE, this

     may cause some "fragile" proofs to fail.

   - The theorems split_<typename>_case and split_<typename>_case_asm

     have been renamed to <typename>.split and <typename>.split_asm.

   - Since default sorts of type variables are now handled correctly,

     some datatype definitions may have to be annotated with explicit

     sort constraints.

   - Primrec definitions no longer require function name and type

     of recursive argument.

 Consider using isatool fixdatatype to adapt your theories and proof

 scripts to the new package (backup your sources first!).

 * HOL/record package: considerably improved implementation; now

 includes concrete syntax for record types, terms, updates; theorems

 for surjective pairing and splitting !!-bound record variables; proof

 support is as follows:

   1) standard conversions (selectors or updates applied to record

 constructor terms) are part of the standard simpset;

   2) inject equations of the form ((x, y) = (x', y')) == x=x' & y=y' are

 made part of standard simpset and claset via addIffs;

   3) a tactic for record field splitting (record_split_tac) is part of

 the standard claset (addSWrapper);

 To get a better idea about these rules you may retrieve them via

 something like 'thms "foo.simps"' or 'thms "foo.iffs"', where "foo" is

 the name of your record type.

 The split tactic 3) conceptually simplifies by the following rule:

   "(!!x. PROP ?P x) == (!!a b. PROP ?P (a, b))"

 Thus any record variable that is bound by meta-all will automatically

 blow up into some record constructor term, consequently the

 simplifications of 1), 2) apply.  Thus force_tac, auto_tac etc. shall

 solve record problems automatically.

 * reorganized the main HOL image: HOL/Integ and String loaded by

 default; theory Main includes everything;

 * automatic simplification of integer sums and comparisons, using cancellation;

 * added option_map_eq_Some and not_Some_eq to the default simpset and claset;

 * added disj_not1 = "(~P | Q) = (P --> Q)" to the default simpset;

 * many new identities for unions, intersections, set difference, etc.;

 * expand_if, expand_split, expand_sum_case and expand_nat_case are now

 called split_if, split_split, split_sum_case and split_nat_case (to go

 with add/delsplits);

 * HOL/Prod introduces simplification procedure unit_eq_proc rewriting

 (?x::unit) = (); this is made part of the default simpset, which COULD

 MAKE EXISTING PROOFS FAIL under rare circumstances (consider

 'Delsimprocs [unit_eq_proc];' as last resort); also note that

 unit_abs_eta_conv is added in order to counter the effect of

 unit_eq_proc on (%u::unit. f u), replacing it by f rather than by

 %u.f();

 * HOL/Fun INCOMPATIBILITY: `inj_onto' is now called `inj_on' (which

 makes more sense);

 * HOL/Set INCOMPATIBILITY: rule `equals0D' is now a well-formed destruct rule;

   It and 'sym RS equals0D' are now in the default  claset, giving automatic

   disjointness reasoning but breaking a few old proofs.

 * HOL/Relation INCOMPATIBILITY: renamed the relational operator r^-1

 to 'converse' from 'inverse' (for compatibility with ZF and some

 literature);

 * HOL/recdef can now declare non-recursive functions, with {} supplied as

 the well-founded relation;

 * HOL/Set INCOMPATIBILITY: the complement of set A is now written -A instead of

     Compl A.  The "Compl" syntax remains available as input syntax for this

     release ONLY.

 * HOL/Update: new theory of function updates:

     f(a:=b) == %x. if x=a then b else f x

 may also be iterated as in f(a:=b,c:=d,...);

 * HOL/Vimage: new theory for inverse image of a function, syntax f-``B;

 * HOL/List:

   - new function list_update written xs[i:=v] that updates the i-th

     list position. May also be iterated as in xs[i:=a,j:=b,...].

   - new function `upt' written [i..j(] which generates the list

     [i,i+1,...,j-1], i.e. the upper bound is excluded. To include the upper

     bound write [i..j], which is a shorthand for [i..j+1(].

   - new lexicographic orderings and corresponding wellfoundedness theorems.

 * HOL/Arith:

   - removed 'pred' (predecessor) function;

   - generalized some theorems about n-1;

   - many new laws about "div" and "mod";

   - new laws about greatest common divisors (see theory ex/Primes);

 * HOL/Relation: renamed the relational operator r^-1 "converse"

 instead of "inverse";

 * HOL/Induct/Multiset: a theory of multisets, including the wellfoundedness

   of the multiset ordering;

 * directory HOL/Real: a construction of the reals using Dedekind cuts

   (not included by default);

 * directory HOL/UNITY: Chandy and Misra's UNITY formalism;

 * directory HOL/Hoare: a new version of Hoare logic which permits many-sorted

   programs, i.e. different program variables may have different types.

 * calling (stac rew i) now fails if "rew" has no effect on the goal

   [previously, this check worked only if the rewrite rule was unconditional]

   Now rew can involve either definitions or equalities (either == or =).

 *** ZF ***

 * theory Main includes everything; INCOMPATIBILITY: theory ZF.thy contains

   only the theorems proved on ZF.ML;

 * ZF INCOMPATIBILITY: rule `equals0D' is now a well-formed destruct rule;

   It and 'sym RS equals0D' are now in the default  claset, giving automatic

   disjointness reasoning but breaking a few old proofs.

 * ZF/Update: new theory of function updates

     with default rewrite rule  f(x:=y) ` z = if(z=x, y, f`z)

   may also be iterated as in f(a:=b,c:=d,...);

 * in  let x=t in u(x), neither t nor u(x) has to be an FOL term.

 * calling (stac rew i) now fails if "rew" has no effect on the goal

   [previously, this check worked only if the rewrite rule was unconditional]

   Now rew can involve either definitions or equalities (either == or =).

 * case_tac provided for compatibility with HOL

     (like the old excluded_middle_tac, but with subgoals swapped)

 *** Internal programming interfaces ***

 * Pure: several new basic modules made available for general use, see

 also src/Pure/README;

 * improved the theory data mechanism to support encapsulation (data

 kind name replaced by private Object.kind, acting as authorization

 key); new type-safe user interface via functor TheoryDataFun; generic

 print_data function becomes basically useless;

 * removed global_names compatibility flag -- all theory declarations

 are qualified by default;

 * module Pure/Syntax now offers quote / antiquote translation

 functions (useful for Hoare logic etc. with implicit dependencies);

 see HOL/ex/Antiquote for an example use;

 * Simplifier now offers conversions (asm_)(full_)rewrite: simpset ->

 cterm -> thm;

 * new tactical CHANGED_GOAL for checking that a tactic modifies a

 subgoal;

 * Display.print_goals function moved to Locale.print_goals;

 * standard print function for goals supports current_goals_markers

 variable for marking begin of proof, end of proof, start of goal; the

 default is ("", "", ""); setting current_goals_markers := ("<proof>",

 "</proof>", "<goal>") causes SGML like tagged proof state printing,

 for example;

 New in Isabelle98 (January 1998)

 --------------------------------

 *** Overview of INCOMPATIBILITIES (see below for more details) ***

 * changed lexical syntax of terms / types: dots made part of long

 identifiers, e.g. "%x.x" no longer possible, should be "%x. x";

 * simpset (and claset) reference variable replaced by functions

 simpset / simpset_ref;

 * no longer supports theory aliases (via merge) and non-trivial

 implicit merge of thms' signatures;

 * most internal names of constants changed due to qualified names;

 * changed Pure/Sequence interface (see Pure/seq.ML);

 *** General Changes ***

 * hierachically structured name spaces (for consts, types, axms, thms

 etc.); new lexical class 'longid' (e.g. Foo.bar.x) may render much of

 old input syntactically incorrect (e.g. "%x.x"); COMPATIBILITY:

 isatool fixdots ensures space after dots (e.g. "%x. x"); set

 long_names for fully qualified output names; NOTE: ML programs

 (special tactics, packages etc.) referring to internal names may have

 to be adapted to cope with fully qualified names; in case of severe

 backward campatibility problems try setting 'global_names' at compile

 time to have enrything declared within a flat name space; one may also

 fine tune name declarations in theories via the 'global' and 'local'

 section;

 * reimplemented the implicit simpset and claset using the new anytype

 data filed in signatures; references simpset:simpset ref etc. are

 replaced by functions simpset:unit->simpset and

 simpset_ref:unit->simpset ref; COMPATIBILITY: use isatool fixclasimp

 to patch your ML files accordingly;

 * HTML output now includes theory graph data for display with Java

 applet or isatool browser; data generated automatically via isatool

 usedir (see -i option, ISABELLE_USEDIR_OPTIONS);

 * defs may now be conditional; improved rewrite_goals_tac to handle

 conditional equations;

 * defs now admits additional type arguments, using TYPE('a) syntax;

 * theory aliases via merge (e.g. M=A+B+C) no longer supported, always

 creates a new theory node; implicit merge of thms' signatures is

 restricted to 'trivial' ones; COMPATIBILITY: one may have to use

 transfer:theory->thm->thm in (rare) cases;

 * improved handling of draft signatures / theories; draft thms (and

 ctyps, cterms) are automatically promoted to real ones;

 * slightly changed interfaces for oracles: admit many per theory, named

 (e.g. oracle foo = mlfun), additional name argument for invoke_oracle;

 * print_goals: optional output of const types (set show_consts and

 show_types);

 * improved output of warnings (###) and errors (***);

 * subgoal_tac displays a warning if the new subgoal has type variables;

 * removed old README and Makefiles;

 * replaced print_goals_ref hook by print_current_goals_fn and result_error_fn;

 * removed obsolete init_pps and init_database;

 * deleted the obsolete tactical STATE, which was declared by

     fun STATE tacfun st = tacfun st st;

 * cd and use now support path variables, e.g. $ISABELLE_HOME, or ~

 (which abbreviates $HOME);

 * changed Pure/Sequence interface (see Pure/seq.ML); COMPATIBILITY:

 use isatool fixseq to adapt your ML programs (this works for fully

 qualified references to the Sequence structure only!);

 * use_thy no longer requires writable current directory; it always

 reloads .ML *and* .thy file, if either one is out of date;

 *** Classical Reasoner ***

 * Clarify_tac, clarify_tac, clarify_step_tac, Clarify_step_tac: new

 tactics that use classical reasoning to simplify a subgoal without

 splitting it into several subgoals;

 * Safe_tac: like safe_tac but uses the default claset;

 *** Simplifier ***

 * added simplification meta rules:

     (asm_)(full_)simplify: simpset -> thm -> thm;

 * simplifier.ML no longer part of Pure -- has to be loaded by object

 logics (again);

 * added prems argument to simplification procedures;

 * HOL, FOL, ZF: added infix function `addsplits':

   instead of `<simpset> setloop (split_tac <thms>)'

   you can simply write `<simpset> addsplits <thms>'

 *** Syntax ***

 * TYPE('a) syntax for type reflection terms;

 * no longer handles consts with name "" -- declare as 'syntax' instead;

 * pretty printer: changed order of mixfix annotation preference (again!);

 * Pure: fixed idt/idts vs. pttrn/pttrns syntactic categories;

 *** HOL ***

 * HOL: there is a new splitter `split_asm_tac' that can be used e.g.

   with `addloop' of the simplifier to faciliate case splitting in premises.

 * HOL/TLA: Stephan Merz's formalization of Lamport's Temporal Logic of Actions;

 * HOL/Auth: new protocol proofs including some for the Internet

   protocol TLS;

 * HOL/Map: new theory of `maps' a la VDM;

 * HOL/simplifier: simplification procedures nat_cancel_sums for

 cancelling out common nat summands from =, <, <= (in)equalities, or

 differences; simplification procedures nat_cancel_factor for

 cancelling common factor from =, <, <= (in)equalities over natural

 sums; nat_cancel contains both kinds of procedures, it is installed by

 default in Arith.thy -- this COULD MAKE EXISTING PROOFS FAIL;

 * HOL/simplifier: terms of the form

   `? x. P1(x) & ... & Pn(x) & x=t & Q1(x) & ... Qn(x)'  (or t=x)

   are rewritten to

   `P1(t) & ... & Pn(t) & Q1(t) & ... Qn(t)',

   and those of the form

   `! x. P1(x) & ... & Pn(x) & x=t & Q1(x) & ... Qn(x) --> R(x)'  (or t=x)

   are rewritten to

   `P1(t) & ... & Pn(t) & Q1(t) & ... Qn(t) --> R(t)',

 * HOL/datatype

   Each datatype `t' now comes with a theorem `split_t_case' of the form

   P(t_case f1 ... fn x) =

      ( (!y1 ... ym1. x = C1 y1 ... ym1 --> P(f1 y1 ... ym1)) &

         ...

        (!y1 ... ymn. x = Cn y1 ... ymn --> P(f1 y1 ... ymn))

      )

   and a theorem `split_t_case_asm' of the form

   P(t_case f1 ... fn x) =

     ~( (? y1 ... ym1. x = C1 y1 ... ym1 & ~P(f1 y1 ... ym1)) |

         ...

        (? y1 ... ymn. x = Cn y1 ... ymn & ~P(f1 y1 ... ymn))

      )

   which can be added to a simpset via `addsplits'. The existing theorems

   expand_list_case and expand_option_case have been renamed to

   split_list_case and split_option_case.

 * HOL/Arithmetic:

   - `pred n' is automatically converted to `n-1'.

     Users are strongly encouraged not to use `pred' any longer,

     because it will disappear altogether at some point.

   - Users are strongly encouraged to write "0 < n" rather than

     "n ~= 0". Theorems and proof tools have been modified towards this

     `standard'.

 * HOL/Lists:

   the function "set_of_list" has been renamed "set" (and its theorems too);

   the function "nth" now takes its arguments in the reverse order and

   has acquired the infix notation "!" as in "xs!n".

 * HOL/Set: UNIV is now a constant and is no longer translated to Compl{};

 * HOL/Set: The operator (UN x.B x) now abbreviates (UN x:UNIV. B x) and its

   specialist theorems (like UN1_I) are gone.  Similarly for (INT x.B x);

 * HOL/record: extensible records with schematic structural subtyping

 (single inheritance); EXPERIMENTAL version demonstrating the encoding,

 still lacks various theorems and concrete record syntax;

 *** HOLCF ***

 * removed "axioms" and "generated by" sections;

 * replaced "ops" section by extended "consts" section, which is capable of

   handling the continuous function space "->" directly;

 * domain package:

   . proves theorems immediately and stores them in the theory,

   . creates hierachical name space,

   . now uses normal mixfix annotations (instead of cinfix...),

   . minor changes to some names and values (for consistency),

   . e.g. cases -> casedist, dists_eq -> dist_eqs, [take_lemma] -> take_lemmas,

   . separator between mutual domain defs: changed "," to "and",

   . improved handling of sort constraints;  now they have to

     appear on the left-hand side of the equations only;

 * fixed LAM <x,y,zs>.b syntax;

 * added extended adm_tac to simplifier in HOLCF -- can now discharge

 adm (%x. P (t x)), where P is chainfinite and t continuous;

 *** FOL and ZF ***

 * FOL: there is a new splitter `split_asm_tac' that can be used e.g.

   with `addloop' of the simplifier to faciliate case splitting in premises.

 * qed_spec_mp, qed_goal_spec_mp, qed_goalw_spec_mp are available, as

 in HOL, they strip ALL and --> from proved theorems;

 New in Isabelle94-8 (May 1997)

 ------------------------------

 *** General Changes ***

 * new utilities to build / run / maintain Isabelle etc. (in parts

 still somewhat experimental); old Makefiles etc. still functional;

 * new 'Isabelle System Manual';

 * INSTALL text, together with ./configure and ./build scripts;

 * reimplemented type inference for greater efficiency, better error

 messages and clean internal interface;

 * prlim command for dealing with lots of subgoals (an easier way of

 setting goals_limit);

 *** Syntax ***

 * supports alternative (named) syntax tables (parser and pretty

 printer); internal interface is provided by add_modesyntax(_i);

 * Pure, FOL, ZF, HOL, HOLCF now support symbolic input and output; to

 be used in conjunction with the Isabelle symbol font; uses the

 "symbols" syntax table;

 * added token_translation interface (may translate name tokens in

 arbitrary ways, dependent on their type (free, bound, tfree, ...) and

 the current print_mode); IMPORTANT: user print translation functions

 are responsible for marking newly introduced bounds

 (Syntax.mark_boundT);

 * token translations for modes "xterm" and "xterm_color" that display

 names in bold, underline etc. or colors (which requires a color

 version of xterm);

 * infixes may now be declared with names independent of their syntax;

 * added typed_print_translation (like print_translation, but may

 access type of constant);

 *** Classical Reasoner ***

 Blast_tac: a new tactic!  It is often more powerful than fast_tac, but has

 some limitations.  Blast_tac...

   + ignores addss, addbefore, addafter; this restriction is intrinsic

   + ignores elimination rules that don't have the correct format

         (the conclusion MUST be a formula variable)

   + ignores types, which can make HOL proofs fail

   + rules must not require higher-order unification, e.g. apply_type in ZF

     [message "Function Var's argument not a bound variable" relates to this]

   + its proof strategy is more general but can actually be slower

 * substitution with equality assumptions no longer permutes other

 assumptions;

 * minor changes in semantics of addafter (now called addaltern); renamed

 setwrapper to setWrapper and compwrapper to compWrapper; added safe wrapper

 (and access functions for it);

 * improved combination of classical reasoner and simplifier:

   + functions for handling clasimpsets

   + improvement of addss: now the simplifier is called _after_ the

     safe steps.

   + safe variant of addss called addSss: uses safe simplifications

     _during_ the safe steps. It is more complete as it allows multiple

     instantiations of unknowns (e.g. with slow_tac).

 *** Simplifier ***

 * added interface for simplification procedures (functions that

 produce *proven* rewrite rules on the fly, depending on current

 redex);

 * ordering on terms as parameter (used for ordered rewriting);

 * new functions delcongs, deleqcongs, and Delcongs. richer rep_ss;

 * the solver is now split into a safe and an unsafe part.

 This should be invisible for the normal user, except that the

 functions setsolver and addsolver have been renamed to setSolver and

 addSolver; added safe_asm_full_simp_tac;

 *** HOL ***

 * a generic induction tactic `induct_tac' which works for all datatypes and

 also for type `nat';

 * a generic case distinction tactic `exhaust_tac' which works for all

 datatypes and also for type `nat';

 * each datatype comes with a function `size';

 * patterns in case expressions allow tuple patterns as arguments to

 constructors, for example `case x of [] => ... | (x,y,z)#ps => ...';

 * primrec now also works with type nat;

 * recdef: a new declaration form, allows general recursive functions to be

 defined in theory files.  See HOL/ex/Fib, HOL/ex/Primes, HOL/Subst/Unify.

 * the constant for negation has been renamed from "not" to "Not" to

 harmonize with FOL, ZF, LK, etc.;

 * HOL/ex/LFilter theory of a corecursive "filter" functional for

 infinite lists;

 * HOL/Modelcheck demonstrates invocation of model checker oracle;

 * HOL/ex/Ring.thy declares cring_simp, which solves equational

 problems in commutative rings, using axiomatic type classes for + and *;

 * more examples in HOL/MiniML and HOL/Auth;

 * more default rewrite rules for quantifiers, union/intersection;

 * a new constant `arbitrary == @x.False';

 * HOLCF/IOA replaces old HOL/IOA;

 * HOLCF changes: derived all rules and arities

   + axiomatic type classes instead of classes

   + typedef instead of faking type definitions

   + eliminated the internal constants less_fun, less_cfun, UU_fun, UU_cfun etc.

   + new axclasses cpo, chfin, flat with flat < chfin < pcpo < cpo < po

   + eliminated the types void, one, tr

   + use unit lift and bool lift (with translations) instead of one and tr

   + eliminated blift from Lift3.thy (use Def instead of blift)

   all eliminated rules are derived as theorems --> no visible changes ;

 *** ZF ***

 * ZF now has Fast_tac, Simp_tac and Auto_tac.  Union_iff is a now a default

 rewrite rule; this may affect some proofs.  eq_cs is gone but can be put back

 as ZF_cs addSIs [equalityI];

 New in Isabelle94-7 (November 96)

 ---------------------------------

 * allowing negative levels (as offsets) in prlev and choplev;

 * super-linear speedup for large simplifications;

 * FOL, ZF and HOL now use miniscoping: rewriting pushes

 quantifications in as far as possible (COULD MAKE EXISTING PROOFS

 FAIL); can suppress it using the command Delsimps (ex_simps @

 all_simps); De Morgan laws are also now included, by default;

 * improved printing of ==>  :  ~:

 * new object-logic "Sequents" adds linear logic, while replacing LK

 and Modal (thanks to Sara Kalvala);

 * HOL/Auth: correctness proofs for authentication protocols;

 * HOL: new auto_tac combines rewriting and classical reasoning (many

 examples on HOL/Auth);

 * HOL: new command AddIffs for declaring theorems of the form P=Q to

 the rewriter and classical reasoner simultaneously;

 * function uresult no longer returns theorems in "standard" format;

 regain previous version by: val uresult = standard o uresult;

 New in Isabelle94-6

 -------------------

 * oracles -- these establish an interface between Isabelle and trusted

 external reasoners, which may deliver results as theorems;

 * proof objects (in particular record all uses of oracles);

 * Simp_tac, Fast_tac, etc. that refer to implicit simpset / claset;

 * "constdefs" section in theory files;

 * "primrec" section (HOL) no longer requires names;

 * internal type "tactic" now simply "thm -> thm Sequence.seq";

 New in Isabelle94-5

 -------------------

 * reduced space requirements;

 * automatic HTML generation from theories;

 * theory files no longer require "..." (quotes) around most types;

 * new examples, including two proofs of the Church-Rosser theorem;

 * non-curried (1994) version of HOL is no longer distributed;

 New in Isabelle94-4

 -------------------

 * greatly reduced space requirements;

 * theory files (.thy) no longer require \...\ escapes at line breaks;

 * searchable theorem database (see the section "Retrieving theorems" on

 page 8 of the Reference Manual);

 * new examples, including Grabczewski's monumental case study of the

 Axiom of Choice;

 * The previous version of HOL renamed to Old_HOL;

 * The new version of HOL (previously called CHOL) uses a curried syntax

 for functions.  Application looks like f a b instead of f(a,b);

 * Mutually recursive inductive definitions finally work in HOL;

 * In ZF, pattern-matching on tuples is now available in all abstractions and

 translates to the operator "split";

 New in Isabelle94-3

 -------------------

 * new infix operator, addss, allowing the classical reasoner to

 perform simplification at each step of its search.  Example:

         fast_tac (cs addss ss)