Isabelle NEWS -- history user-relevant changes

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

New in this Isabelle version

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

*** Pure ***

* Recovered hiding of consts, which was accidentally broken in

Isabelle2007.  Potential INCOMPATIBILITY, ``hide const c'' really

makes c inaccessible; consider using ``hide (open) const c'' instead.

* Command 'instance': attached definitions now longer accepted.

INCOMPATIBILITY, use proper 'instantiation' target.

* Keyword 'code_exception' now named 'code_abort'.  INCOMPATIBILITY.

* Removed exotic 'token_translation' command.  INCOMPATIBILITY, use ML

interface instead.

*** HOL ***

* Methods "case_tac" and "induct_tac" now refer to the very same rules

as the structured Isar versions "cases" and "induct", cf. the

corresponding "cases" and "induct" attributes.  Mutual induction rules

are now presented as a list of individual projections

(e.g. foo_bar.inducts for types foo and bar); the old format with

explicit HOL conjunction is no longer supported.  INCOMPATIBILITY, in

rare situations a different rule is selected --- notably nested tuple

elimination instead of former prod.exhaust: use explicit (case_tac t

rule: prod.exhaust) here.

* Attributes "cases", "induct", "coinduct" support "del" option.

* Removed fact "case_split_thm", which duplicates "case_split".

* Command 'rep_datatype': instead of theorem names the command now

takes a list of terms denoting the constructors of the type to be

represented as datatype.  The characteristic theorems have to be

proven.  INCOMPATIBILITY.  Also observe that the following theorems

have disappeared in favour of existing ones:

    unit_induct                 ~> unit.induct

    prod_induct                 ~> prod.induct

    sum_induct                  ~> sum.induct

    Suc_Suc_eq                  ~> nat.inject

    Suc_not_Zero Zero_not_Suc   ~> nat.distinct

* Library/Nat_Infinity: added addition, numeral syntax and more

instantiations for algebraic structures.  Removed some duplicate

theorems.  Changes in simp rules.  INCOMPATIBILITY.

*** ML ***

* Rules and tactics that read instantiations (read_instantiate,

res_inst_tac, thin_tac, subgoal_tac etc.) now demand a proper proof

context, which is required for parsing and type-checking.  Moreover,

the variables are specified as plain indexnames, not string encodings

thereof.  INCOMPATIBILITY.

* Disposed old type and term read functions (Sign.read_def_typ,

Sign.read_typ, Sign.read_def_terms, Sign.read_term,

Thm.read_def_cterms, Thm.read_cterm etc.).  INCOMPATIBILITY, should

use regular Syntax.read_typ, Syntax.read_term, Syntax.read_typ_global,

Syntax.read_term_global etc.; see also OldGoals.read_term as last

resort for legacy applications.

* Antiquotations: block-structured compilation context indicated by

\<lbrace> ... \<rbrace>, and additional antiquotation forms:

  @{let ?pat = term}

  @{note name = fact}

  @{thm name [attribs]}

  @{thms name [attribs]}

New in Isabelle2008 (June 2008)

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

*** General ***

* The Isabelle/Isar Reference Manual (isar-ref) has been reorganized

and updated, with formally checked references as hyperlinks.

* Theory loader: use_thy (and similar operations) no longer set the

implicit ML context, which was occasionally hard to predict and in

conflict with concurrency.  INCOMPATIBILITY, use ML within Isar which

provides a proper context already.

* Theory loader: old-style ML proof scripts being *attached* to a thy

file are no longer supported.  INCOMPATIBILITY, regular 'uses' and

'use' within a theory file will do the job.

* Name space merge now observes canonical order, i.e. the second space

is inserted into the first one, while existing entries in the first

space take precedence.  INCOMPATIBILITY in rare situations, may try to

swap theory imports.

* Syntax: symbol \<chi> is now considered a letter.  Potential

INCOMPATIBILITY in identifier syntax etc.

* Outer syntax: string tokens no longer admit escaped white space,

which was an accidental (undocumented) feature.  INCOMPATIBILITY, use

white space without escapes.

* Outer syntax: string tokens may contain arbitrary character codes

specified via 3 decimal digits (as in SML).  E.g. "foo\095bar" for

"foo_bar".

*** Pure ***

* Context-dependent token translations.  Default setup reverts locally

fixed variables, and adds hilite markup for undeclared frees.

* Unused theorems can be found using the new command 'unused_thms'.

There are three ways of invoking it:

(1) unused_thms

     Only finds unused theorems in the current theory.

(2) unused_thms thy_1 ... thy_n -

     Finds unused theorems in the current theory and all of its ancestors,

     excluding the theories thy_1 ... thy_n and all of their ancestors.

(3) unused_thms thy_1 ... thy_n - thy'_1 ... thy'_m

     Finds unused theorems in the theories thy'_1 ... thy'_m and all of

     their ancestors, excluding the theories thy_1 ... thy_n and all of

     their ancestors.

In order to increase the readability of the list produced by

unused_thms, theorems that have been created by a particular instance

of a theory command such as 'inductive' or 'function' are considered

to belong to the same "group", meaning that if at least one theorem in

this group is used, the other theorems in the same group are no longer

reported as unused.  Moreover, if all theorems in the group are

unused, only one theorem in the group is displayed.

Note that proof objects have to be switched on in order for

unused_thms to work properly (i.e. !proofs must be >= 1, which is

usually the case when using Proof General with the default settings).

* Authentic naming of facts disallows ad-hoc overwriting of previous

theorems within the same name space.  INCOMPATIBILITY, need to remove

duplicate fact bindings, or even accidental fact duplications.  Note

that tools may maintain dynamically scoped facts systematically, using

PureThy.add_thms_dynamic.

* Command 'hide' now allows to hide from "fact" name space as well.

* Eliminated destructive theorem database, simpset, claset, and

clasimpset.  Potential INCOMPATIBILITY, really need to observe linear

update of theories within ML code.

* Eliminated theory ProtoPure and CPure, leaving just one Pure theory.

INCOMPATIBILITY, object-logics depending on former Pure require

additional setup PureThy.old_appl_syntax_setup; object-logics

depending on former CPure need to refer to Pure.

* Commands 'use' and 'ML' are now purely functional, operating on

theory/local_theory.  Removed former 'ML_setup' (on theory), use 'ML'

instead.  Added 'ML_val' as mere diagnostic replacement for 'ML'.

INCOMPATIBILITY.

* Command 'setup': discontinued implicit version with ML reference.

* Instantiation target allows for simultaneous specification of class

instance operations together with an instantiation proof.

Type-checking phase allows to refer to class operations uniformly.

See src/HOL/Complex/Complex.thy for an Isar example and

src/HOL/Library/Eval.thy for an ML example.

* Indexing of literal facts: be more serious about including only

facts from the visible specification/proof context, but not the

background context (locale etc.).  Affects `prop` notation and method

"fact".  INCOMPATIBILITY: need to name facts explicitly in rare

situations.

* Method "cases", "induct", "coinduct": removed obsolete/undocumented

"(open)" option, which used to expose internal bound variables to the

proof text.

* Isar statements: removed obsolete case "rule_context".

INCOMPATIBILITY, better use explicit fixes/assumes.

* Locale proofs: default proof step now includes 'unfold_locales';

hence 'proof' without argument may be used to unfold locale

predicates.

*** Document preparation ***

* Simplified pdfsetup.sty: color/hyperref is used unconditionally for

both pdf and dvi (hyperlinks usually work in xdvi as well); removed

obsolete thumbpdf setup (contemporary PDF viewers do this on the

spot); renamed link color from "darkblue" to "linkcolor" (default

value unchanged, can be redefined via \definecolor); no longer sets

"a4paper" option (unnecessary or even intrusive).

* Antiquotation @{lemma A method} proves proposition A by the given

method (either a method name or a method name plus (optional) method

arguments in parentheses) and prints A just like @{prop A}.

*** HOL ***

* New primrec package.  Specification syntax conforms in style to

definition/function/....  No separate induction rule is provided.  The

"primrec" command distinguishes old-style and new-style specifications

by syntax.  The former primrec package is now named OldPrimrecPackage.

When adjusting theories, beware: constants stemming from new-style

primrec specifications have authentic syntax.

* Metis prover is now an order of magnitude faster, and also works

with multithreading.

* Metis: the maximum number of clauses that can be produced from a

theorem is now given by the attribute max_clauses.  Theorems that

exceed this number are ignored, with a warning printed.

* Sledgehammer no longer produces structured proofs by default. To

enable, declare [[sledgehammer_full = true]].  Attributes

reconstruction_modulus, reconstruction_sorts renamed

sledgehammer_modulus, sledgehammer_sorts.  INCOMPATIBILITY.

* Method "induct_scheme" derives user-specified induction rules

from well-founded induction and completeness of patterns. This factors

out some operations that are done internally by the function package

and makes them available separately.  See

src/HOL/ex/Induction_Scheme.thy for examples.

* More flexible generation of measure functions for termination

proofs: Measure functions can be declared by proving a rule of the

form "is_measure f" and giving it the [measure_function] attribute.

The "is_measure" predicate is logically meaningless (always true), and

just guides the heuristic.  To find suitable measure functions, the

termination prover sets up the goal "is_measure ?f" of the appropriate

type and generates all solutions by prolog-style backwards proof using

the declared rules.

This setup also deals with rules like 

  "is_measure f ==> is_measure (list_size f)"

which accommodates nested datatypes that recurse through lists.

Similar rules are predeclared for products and option types.

* Turned the type of sets "'a set" into an abbreviation for "'a => bool"

  INCOMPATIBILITIES:

  - Definitions of overloaded constants on sets have to be replaced by

    definitions on => and bool.

  - Some definitions of overloaded operators on sets can now be proved

    using the definitions of the operators on => and bool.  Therefore,

    the following theorems have been renamed:

      subset_def   -> subset_eq

      psubset_def  -> psubset_eq

      set_diff_def -> set_diff_eq

      Compl_def    -> Compl_eq

      Sup_set_def  -> Sup_set_eq

      Inf_set_def  -> Inf_set_eq

      sup_set_def  -> sup_set_eq

      inf_set_def  -> inf_set_eq

  - Due to the incompleteness of the HO unification algorithm, some

    rules such as subst may require manual instantiation, if some of

    the unknowns in the rule is a set.

  - Higher order unification and forward proofs:

    The proof pattern

      have "P (S::'a set)" <...>

      then have "EX S. P S" ..

    no longer works (due to the incompleteness of the HO unification

    algorithm) and must be replaced by the pattern

      have "EX S. P S"

      proof

        show "P S" <...>

      qed

  - Calculational reasoning with subst (or similar rules):

    The proof pattern

      have "P (S::'a set)" <...>

      also have "S = T" <...>

      finally have "P T" .

    no longer works (for similar reasons as the previous example) and

    must be replaced by something like

      have "P (S::'a set)" <...>

      moreover have "S = T" <...>

      ultimately have "P T" by simp

  - Tactics or packages written in ML code:

    Code performing pattern matching on types via

      Type ("set", [T]) => ...

    must be rewritten. Moreover, functions like strip_type or

    binder_types no longer return the right value when applied to a

    type of the form

      T1 => ... => Tn => U => bool

    rather than

      T1 => ... => Tn => U set

* Merged theories Wellfounded_Recursion, Accessible_Part and

Wellfounded_Relations to theory Wellfounded.

* Explicit class "eq" for executable equality.  INCOMPATIBILITY.

* Class finite no longer treats UNIV as class parameter.  Use class

enum from theory Library/Enum instead to achieve a similar effect.

INCOMPATIBILITY.

* Theory List: rule list_induct2 now has explicitly named cases "Nil"

and "Cons".  INCOMPATIBILITY.

* HOL (and FOL): renamed variables in rules imp_elim and swap.

Potential INCOMPATIBILITY.

* Theory Product_Type: duplicated lemmas split_Pair_apply and

injective_fst_snd removed, use split_eta and prod_eqI instead.

Renamed upd_fst to apfst and upd_snd to apsnd.  INCOMPATIBILITY.

* Theory Nat: removed redundant lemmas that merely duplicate lemmas of

the same name in theory Orderings:

  less_trans

  less_linear

  le_imp_less_or_eq

  le_less_trans

  less_le_trans

  less_not_sym

  less_asym

Renamed less_imp_le to less_imp_le_nat, and less_irrefl to

less_irrefl_nat.  Potential INCOMPATIBILITY due to more general types

and different variable names.

* Library/Option_ord.thy: Canonical order on option type.

* Library/RBT.thy: Red-black trees, an efficient implementation of

finite maps.

* Library/Countable.thy: Type class for countable types.

* Theory Int: The representation of numerals has changed.  The infix

operator BIT and the bit datatype with constructors B0 and B1 have

disappeared.  INCOMPATIBILITY, use "Int.Bit0 x" and "Int.Bit1 y" in

place of "x BIT bit.B0" and "y BIT bit.B1", respectively.  Theorems

involving BIT, B0, or B1 have been renamed with "Bit0" or "Bit1"

accordingly.

* Theory Nat: definition of <= and < on natural numbers no longer

depend on well-founded relations.  INCOMPATIBILITY.  Definitions

le_def and less_def have disappeared.  Consider lemmas not_less

[symmetric, where ?'a = nat] and less_eq [symmetric] instead.

* Theory Finite_Set: locales ACf, ACe, ACIf, ACIfSL and ACIfSLlin

(whose purpose mainly is for various fold_set functionals) have been

abandoned in favor of the existing algebraic classes

ab_semigroup_mult, comm_monoid_mult, ab_semigroup_idem_mult,

lower_semilattice (resp. upper_semilattice) and linorder.

INCOMPATIBILITY.

* Theory Transitive_Closure: induct and cases rules now declare proper

case_names ("base" and "step").  INCOMPATIBILITY.

* Theorem Inductive.lfp_ordinal_induct generalized to complete

lattices.  The form set-specific version is available as

Inductive.lfp_ordinal_induct_set.

* Renamed theorems "power.simps" to "power_int.simps".

INCOMPATIBILITY.

* Class semiring_div provides basic abstract properties of semirings

with division and modulo operations.  Subsumes former class dvd_mod.

* Merged theories IntDef, Numeral and IntArith into unified theory

Int.  INCOMPATIBILITY.

* Theory Library/Code_Index: type "index" now represents natural

numbers rather than integers.  INCOMPATIBILITY.

* New class "uminus" with operation "uminus" (split of from class

"minus" which now only has operation "minus", binary).

INCOMPATIBILITY.

* Constants "card", "internal_split", "option_map" now with authentic

syntax.  INCOMPATIBILITY.

* Definitions subset_def, psubset_def, set_diff_def, Compl_def,

le_bool_def, less_bool_def, le_fun_def, less_fun_def, inf_bool_def,

sup_bool_def, Inf_bool_def, Sup_bool_def, inf_fun_def, sup_fun_def,

Inf_fun_def, Sup_fun_def, inf_set_def, sup_set_def, Inf_set_def,

Sup_set_def, le_def, less_def, option_map_def now with object

equality.  INCOMPATIBILITY.

* Records. Removed K_record, and replaced it by pure lambda term

%x. c. The simplifier setup is now more robust against eta expansion.

INCOMPATIBILITY: in cases explicitly referring to K_record.

* Library/Multiset: {#a, b, c#} abbreviates {#a#} + {#b#} + {#c#}.

* Library/ListVector: new theory of arithmetic vector operations.

* Library/Order_Relation: new theory of various orderings as sets of

pairs.  Defines preorders, partial orders, linear orders and

well-orders on sets and on types.

*** ZF ***

* Renamed some theories to allow to loading both ZF and HOL in the

same session:

  Datatype  -> Datatype_ZF

  Inductive -> Inductive_ZF

  Int       -> Int_ZF

  IntDiv    -> IntDiv_ZF

  Nat       -> Nat_ZF

  List      -> List_ZF

  Main      -> Main_ZF

INCOMPATIBILITY: ZF theories that import individual theories below

Main might need to be adapted.  Regular theory Main is still

available, as trivial extension of Main_ZF.

*** ML ***

* ML within Isar: antiquotation @{const name} or @{const

name(typargs)} produces statically-checked Const term.

* Functor NamedThmsFun: data is available to the user as dynamic fact

(of the same name).  Removed obsolete print command.

* Removed obsolete "use_legacy_bindings" function.

* The ``print mode'' is now a thread-local value derived from a global

template (the former print_mode reference), thus access becomes

non-critical.  The global print_mode reference is for session

management only; user-code should use print_mode_value,

print_mode_active, PrintMode.setmp etc.  INCOMPATIBILITY.

* Functions system/system_out provide a robust way to invoke external

shell commands, with propagation of interrupts (requires Poly/ML 5.2).

Do not use OS.Process.system etc. from the basis library!

*** System ***

* Default settings: PROOFGENERAL_OPTIONS no longer impose xemacs ---

in accordance with Proof General 3.7, which prefers GNU emacs.

* isatool tty runs Isabelle process with plain tty interaction;

optional line editor may be specified via ISABELLE_LINE_EDITOR

setting, the default settings attempt to locate "ledit" and "rlwrap".

* isatool browser now works with Cygwin as well, using general

"javapath" function defined in Isabelle process environment.

* YXML notation provides a simple and efficient alternative to

standard XML transfer syntax.  See src/Pure/General/yxml.ML and

isatool yxml as described in the Isabelle system manual.

* JVM class isabelle.IsabelleProcess (located in Isabelle/lib/classes)

provides general wrapper for managing an Isabelle process in a robust

fashion, with ``cooked'' output from stdin/stderr.

* Rudimentary Isabelle plugin for jEdit (see Isabelle/lib/jedit),

based on Isabelle/JVM process wrapper (see Isabelle/lib/classes).

* Removed obsolete THIS_IS_ISABELLE_BUILD feature.  NB: the documented

way of changing the user's settings is via

ISABELLE_HOME_USER/etc/settings, which is a fully featured bash

script.

* Multithreading.max_threads := 0 refers to the number of actual CPU

cores of the underlying machine, which is a good starting point for

optimal performance tuning.  The corresponding usedir option -M allows

"max" as an alias for "0".  WARNING: does not work on certain versions

of Mac OS (with Poly/ML 5.1).

* isabelle-process: non-ML sessions are run with "nice", to reduce the

adverse effect of Isabelle flooding interactive front-ends (notably

ProofGeneral / XEmacs).

New in Isabelle2007 (November 2007)

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

*** General ***

* More uniform information about legacy features, notably a

warning/error of "Legacy feature: ...", depending on the state of the

tolerate_legacy_features flag (default true). FUTURE INCOMPATIBILITY:

legacy features will disappear eventually.

* Theory syntax: the header format ``theory A = B + C:'' has been

discontinued in favour of ``theory A imports B C begin''.  Use isatool

fixheaders to convert existing theory files.  INCOMPATIBILITY.

* Theory syntax: the old non-Isar theory file format has been

discontinued altogether.  Note that ML proof scripts may still be used

with Isar theories; migration is usually quite simple with the ML

function use_legacy_bindings.  INCOMPATIBILITY.

* Theory syntax: some popular names (e.g. 'class', 'declaration',

'fun', 'help', 'if') are now keywords.  INCOMPATIBILITY, use double

quotes.

* Theory loader: be more serious about observing the static theory

header specifications (including optional directories), but not the

accidental file locations of previously successful loads.  The strict

update policy of former update_thy is now already performed by

use_thy, so the former has been removed; use_thys updates several

theories simultaneously, just as 'imports' within a theory header

specification, but without merging the results.  Potential

INCOMPATIBILITY: may need to refine theory headers and commands

ROOT.ML which depend on load order.

* Theory loader: optional support for content-based file

identification, instead of the traditional scheme of full physical

path plus date stamp; configured by the ISABELLE_FILE_IDENT setting

(cf. the system manual).  The new scheme allows to work with

non-finished theories in persistent session images, such that source

files may be moved later on without requiring reloads.

* Theory loader: old-style ML proof scripts being *attached* to a thy

file (with the same base name as the theory) are considered a legacy

feature, which will disappear eventually. Even now, the theory loader

no longer maintains dependencies on such files.

* Syntax: the scope for resolving ambiguities via type-inference is

now limited to individual terms, instead of whole simultaneous

specifications as before. This greatly reduces the complexity of the

syntax module and improves flexibility by separating parsing and

type-checking. INCOMPATIBILITY: additional type-constraints (explicit

'fixes' etc.) are required in rare situations.

* Syntax: constants introduced by new-style packages ('definition',

'abbreviation' etc.) are passed through the syntax module in

``authentic mode''. This means that associated mixfix annotations

really stick to such constants, independently of potential name space

ambiguities introduced later on. INCOMPATIBILITY: constants in parse

trees are represented slightly differently, may need to adapt syntax

translations accordingly. Use CONST marker in 'translations' and

@{const_syntax} antiquotation in 'parse_translation' etc.

* Legacy goal package: reduced interface to the bare minimum required

to keep existing proof scripts running.  Most other user-level

functions are now part of the OldGoals structure, which is *not* open

by default (consider isatool expandshort before open OldGoals).

Removed top_sg, prin, printyp, pprint_term/typ altogether, because

these tend to cause confusion about the actual goal (!) context being

used here, which is not necessarily the same as the_context().

* Command 'find_theorems': supports "*" wild-card in "name:"

criterion; "with_dups" option.  Certain ProofGeneral versions might

support a specific search form (see ProofGeneral/CHANGES).

* The ``prems limit'' option (cf. ProofContext.prems_limit) is now -1

by default, which means that "prems" (and also "fixed variables") are

suppressed from proof state output.  Note that the ProofGeneral

settings mechanism allows to change and save options persistently, but

older versions of Isabelle will fail to start up if a negative prems

limit is imposed.

* Local theory targets may be specified by non-nested blocks of

``context/locale/class ... begin'' followed by ``end''.  The body may

contain definitions, theorems etc., including any derived mechanism

that has been implemented on top of these primitives.  This concept

generalizes the existing ``theorem (in ...)'' towards more versatility

and scalability.

* Proof General interface: proper undo of final 'end' command;

discontinued Isabelle/classic mode (ML proof scripts).

*** Document preparation ***

* Added antiquotation @{theory name} which prints the given name,

after checking that it refers to a valid ancestor theory in the

current context.

* Added antiquotations @{ML_type text} and @{ML_struct text} which

check the given source text as ML type/structure, printing verbatim.

* Added antiquotation @{abbrev "c args"} which prints the abbreviation

"c args == rhs" given in the current context.  (Any number of

arguments may be given on the LHS.)

*** Pure ***

* The 'class' package offers a combination of axclass and locale to

achieve Haskell-like type classes in Isabelle.  Definitions and

theorems within a class context produce both relative results (with

implicit parameters according to the locale context), and polymorphic

constants with qualified polymorphism (according to the class

context).  Within the body context of a 'class' target, a separate

syntax layer ("user space type system") takes care of converting

between global polymorphic consts and internal locale representation.

See src/HOL/ex/Classpackage.thy for examples (as well as main HOL).

"isatool doc classes" provides a tutorial.

* Generic code generator framework allows to generate executable

code for ML and Haskell (including Isabelle classes).  A short usage

sketch:

    internal compilation:

        export_code <list of constants (term syntax)> in SML

    writing SML code to a file:

        export_code <list of constants (term syntax)> in SML <filename>

    writing OCaml code to a file:

        export_code <list of constants (term syntax)> in OCaml <filename>

    writing Haskell code to a bunch of files:

        export_code <list of constants (term syntax)> in Haskell <filename>

    evaluating closed propositions to True/False using code generation:

        method ``eval''

Reasonable default setup of framework in HOL.

Theorem attributs for selecting and transforming function equations theorems:

    [code fun]:        select a theorem as function equation for a specific constant

    [code fun del]:    deselect a theorem as function equation for a specific constant

    [code inline]:     select an equation theorem for unfolding (inlining) in place

    [code inline del]: deselect an equation theorem for unfolding (inlining) in place

User-defined serializations (target in {SML, OCaml, Haskell}):

    code_const <and-list of constants (term syntax)>

      {(target) <and-list of const target syntax>}+

    code_type <and-list of type constructors>

      {(target) <and-list of type target syntax>}+

    code_instance <and-list of instances>

      {(target)}+

        where instance ::= <type constructor> :: <class>

    code_class <and_list of classes>

      {(target) <and-list of class target syntax>}+

        where class target syntax ::= <class name> {where {<classop> == <target syntax>}+}?

code_instance and code_class only are effective to target Haskell.

For example usage see src/HOL/ex/Codegenerator.thy and

src/HOL/ex/Codegenerator_Pretty.thy.  A separate tutorial on code

generation from Isabelle/HOL theories is available via "isatool doc

codegen".

* Code generator: consts in 'consts_code' Isar commands are now

referred to by usual term syntax (including optional type

annotations).

* Command 'no_translations' removes translation rules from theory

syntax.

* Overloaded definitions are now actually checked for acyclic

dependencies.  The overloading scheme is slightly more general than

that of Haskell98, although Isabelle does not demand an exact

correspondence to type class and instance declarations.

INCOMPATIBILITY, use ``defs (unchecked overloaded)'' to admit more

exotic versions of overloading -- at the discretion of the user!

Polymorphic constants are represented via type arguments, i.e. the

instantiation that matches an instance against the most general

declaration given in the signature.  For example, with the declaration

c :: 'a => 'a => 'a, an instance c :: nat => nat => nat is represented

as c(nat).  Overloading is essentially simultaneous structural

recursion over such type arguments.  Incomplete specification patterns

impose global constraints on all occurrences, e.g. c('a * 'a) on the

LHS means that more general c('a * 'b) will be disallowed on any RHS.

Command 'print_theory' outputs the normalized system of recursive

equations, see section "definitions".

* Configuration options are maintained within the theory or proof

context (with name and type bool/int/string), providing a very simple

interface to a poor-man's version of general context data.  Tools may

declare options in ML (e.g. using Attrib.config_int) and then refer to

these values using Config.get etc.  Users may change options via an

associated attribute of the same name.  This form of context

declaration works particularly well with commands 'declare' or

'using', for example ``declare [[foo = 42]]''.  Thus it has become

very easy to avoid global references, which would not observe Isar

toplevel undo/redo and fail to work with multithreading.

Various global ML references of Pure and HOL have been turned into

configuration options:

  Unify.search_bound		unify_search_bound

  Unify.trace_bound		unify_trace_bound

  Unify.trace_simp		unify_trace_simp

  Unify.trace_types		unify_trace_types

  Simplifier.simp_depth_limit	simp_depth_limit

  Blast.depth_limit		blast_depth_limit

  DatatypeProp.dtK		datatype_distinctness_limit

  fast_arith_neq_limit  	fast_arith_neq_limit

  fast_arith_split_limit	fast_arith_split_limit

* Named collections of theorems may be easily installed as context

data using the functor NamedThmsFun (see also

src/Pure/Tools/named_thms.ML).  The user may add or delete facts via

attributes; there is also a toplevel print command.  This facility is

just a common case of general context data, which is the preferred way

for anything more complex than just a list of facts in canonical

order.

* Isar: command 'declaration' augments a local theory by generic

declaration functions written in ML.  This enables arbitrary content

being added to the context, depending on a morphism that tells the

difference of the original declaration context wrt. the application

context encountered later on.

* Isar: proper interfaces for simplification procedures.  Command

'simproc_setup' declares named simprocs (with match patterns, and body

text in ML).  Attribute "simproc" adds/deletes simprocs in the current

context.  ML antiquotation @{simproc name} retrieves named simprocs.

* Isar: an extra pair of brackets around attribute declarations

abbreviates a theorem reference involving an internal dummy fact,

which will be ignored later --- only the effect of the attribute on

the background context will persist.  This form of in-place

declarations is particularly useful with commands like 'declare' and

'using', for example ``have A using [[simproc a]] by simp''.

* Isar: method "assumption" (and implicit closing of subproofs) now

takes simple non-atomic goal assumptions into account: after applying

an assumption as a rule the resulting subgoals are solved by atomic

assumption steps.  This is particularly useful to finish 'obtain'

goals, such as "!!x. (!!x. P x ==> thesis) ==> P x ==> thesis",

without referring to the original premise "!!x. P x ==> thesis" in the

Isar proof context.  POTENTIAL INCOMPATIBILITY: method "assumption" is

more permissive.

* Isar: implicit use of prems from the Isar proof context is

considered a legacy feature.  Common applications like ``have A .''

may be replaced by ``have A by fact'' or ``note `A`''.  In general,

referencing facts explicitly here improves readability and

maintainability of proof texts.

* Isar: improper proof element 'guess' is like 'obtain', but derives

the obtained context from the course of reasoning!  For example:

  assume "EX x y. A x & B y"   -- "any previous fact"

  then guess x and y by clarify

This technique is potentially adventurous, depending on the facts and

proof tools being involved here.

* Isar: known facts from the proof context may be specified as literal

propositions, using ASCII back-quote syntax.  This works wherever

named facts used to be allowed so far, in proof commands, proof

methods, attributes etc.  Literal facts are retrieved from the context

according to unification of type and term parameters.  For example,

provided that "A" and "A ==> B" and "!!x. P x ==> Q x" are known

theorems in the current context, then these are valid literal facts:

`A` and `A ==> B` and `!!x. P x ==> Q x" as well as `P a ==> Q a` etc.

There is also a proof method "fact" which does the same composition

for explicit goal states, e.g. the following proof texts coincide with

certain special cases of literal facts:

  have "A" by fact                 ==  note `A`

  have "A ==> B" by fact           ==  note `A ==> B`

  have "!!x. P x ==> Q x" by fact  ==  note `!!x. P x ==> Q x`

  have "P a ==> Q a" by fact       ==  note `P a ==> Q a`

* Isar: ":" (colon) is no longer a symbolic identifier character in

outer syntax.  Thus symbolic identifiers may be used without

additional white space in declarations like this: ``assume *: A''.

* Isar: 'print_facts' prints all local facts of the current context,

both named and unnamed ones.

* Isar: 'def' now admits simultaneous definitions, e.g.:

  def x == "t" and y == "u"

* Isar: added command 'unfolding', which is structurally similar to

'using', but affects both the goal state and facts by unfolding given

rewrite rules.  Thus many occurrences of the 'unfold' method or

'unfolded' attribute may be replaced by first-class proof text.

* Isar: methods 'unfold' / 'fold', attributes 'unfolded' / 'folded',

and command 'unfolding' now all support object-level equalities

(potentially conditional).  The underlying notion of rewrite rule is

analogous to the 'rule_format' attribute, but *not* that of the

Simplifier (which is usually more generous).

* Isar: the new attribute [rotated n] (default n = 1) rotates the

premises of a theorem by n. Useful in conjunction with drule.

* Isar: the goal restriction operator [N] (default N = 1) evaluates a

method expression within a sandbox consisting of the first N

sub-goals, which need to exist.  For example, ``simp_all [3]''

simplifies the first three sub-goals, while (rule foo, simp_all)[]

simplifies all new goals that emerge from applying rule foo to the

originally first one.

* Isar: schematic goals are no longer restricted to higher-order

patterns; e.g. ``lemma "?P(?x)" by (rule TrueI)'' now works as

expected.

* Isar: the conclusion of a long theorem statement is now either

'shows' (a simultaneous conjunction, as before), or 'obtains'

(essentially a disjunction of cases with local parameters and

assumptions).  The latter allows to express general elimination rules

adequately; in this notation common elimination rules look like this:

  lemma exE:    -- "EX x. P x ==> (!!x. P x ==> thesis) ==> thesis"

    assumes "EX x. P x"

    obtains x where "P x"

  lemma conjE:  -- "A & B ==> (A ==> B ==> thesis) ==> thesis"

    assumes "A & B"

    obtains A and B

  lemma disjE:  -- "A | B ==> (A ==> thesis) ==> (B ==> thesis) ==> thesis"

    assumes "A | B"

    obtains

      A

    | B

The subsequent classical rules even refer to the formal "thesis"

explicitly:

  lemma classical:     -- "(~ thesis ==> thesis) ==> thesis"

    obtains "~ thesis"

  lemma Peirce's_Law:  -- "((thesis ==> something) ==> thesis) ==> thesis"

    obtains "thesis ==> something"

The actual proof of an 'obtains' statement is analogous to that of the

Isar proof element 'obtain', only that there may be several cases.

Optional case names may be specified in parentheses; these will be

available both in the present proof and as annotations in the

resulting rule, for later use with the 'cases' method (cf. attribute

case_names).

* Isar: the assumptions of a long theorem statement are available as

"assms" fact in the proof context.  This is more appropriate than the

(historical) "prems", which refers to all assumptions of the current

context, including those from the target locale, proof body etc.

* Isar: 'print_statement' prints theorems from the current theory or

proof context in long statement form, according to the syntax of a

top-level lemma.

* Isar: 'obtain' takes an optional case name for the local context

introduction rule (default "that").

* Isar: removed obsolete 'concl is' patterns.  INCOMPATIBILITY, use

explicit (is "_ ==> ?foo") in the rare cases where this still happens

to occur.

* Pure: syntax "CONST name" produces a fully internalized constant

according to the current context.  This is particularly useful for

syntax translations that should refer to internal constant

representations independently of name spaces.

* Pure: syntax constant for foo (binder "FOO ") is called "foo_binder"

instead of "FOO ". This allows multiple binder declarations to coexist

in the same context.  INCOMPATIBILITY.

* Isar/locales: 'notation' provides a robust interface to the 'syntax'

primitive that also works in a locale context (both for constants and

fixed variables). Type declaration and internal syntactic representation

of given constants retrieved from the context. Likewise, the

'no_notation' command allows to remove given syntax annotations from the

current context.

* Isar/locales: new derived specification elements 'axiomatization',

'definition', 'abbreviation', which support type-inference, admit

object-level specifications (equality, equivalence).  See also the

isar-ref manual.  Examples:

  axiomatization

    eq  (infix "===" 50) where

    eq_refl: "x === x" and eq_subst: "x === y ==> P x ==> P y"

  definition "f x y = x + y + 1"

  definition g where "g x = f x x"

  abbreviation

    neq  (infix "=!=" 50) where

    "x =!= y == ~ (x === y)"

These specifications may be also used in a locale context.  Then the

constants being introduced depend on certain fixed parameters, and the

constant name is qualified by the locale base name.  An internal

abbreviation takes care for convenient input and output, making the

parameters implicit and using the original short name.  See also

src/HOL/ex/Abstract_NAT.thy for an example of deriving polymorphic

entities from a monomorphic theory.

Presently, abbreviations are only available 'in' a target locale, but

not inherited by general import expressions.  Also note that

'abbreviation' may be used as a type-safe replacement for 'syntax' +

'translations' in common applications.  The "no_abbrevs" print mode

prevents folding of abbreviations in term output.

Concrete syntax is attached to specified constants in internal form,

independently of name spaces.  The parse tree representation is

slightly different -- use 'notation' instead of raw 'syntax', and

'translations' with explicit "CONST" markup to accommodate this.

* Pure/Isar: unified syntax for new-style specification mechanisms

(e.g.  'definition', 'abbreviation', or 'inductive' in HOL) admits

full type inference and dummy patterns ("_").  For example:

  definition "K x _ = x"

  inductive conj for A B

  where "A ==> B ==> conj A B"

* Pure: command 'print_abbrevs' prints all constant abbreviations of

the current context.  Print mode "no_abbrevs" prevents inversion of

abbreviations on output.

* Isar/locales: improved parameter handling: use of locales "var" and

"struct" no longer necessary; - parameter renamings are no longer

required to be injective.  For example, this allows to define

endomorphisms as locale endom = homom mult mult h.

* Isar/locales: changed the way locales with predicates are defined.

Instead of accumulating the specification, the imported expression is

now an interpretation.  INCOMPATIBILITY: different normal form of

locale expressions.  In particular, in interpretations of locales with

predicates, goals repesenting already interpreted fragments are not

removed automatically.  Use methods `intro_locales' and

`unfold_locales'; see below.

* Isar/locales: new methods `intro_locales' and `unfold_locales'

provide backward reasoning on locales predicates.  The methods are

aware of interpretations and discharge corresponding goals.

`intro_locales' is less aggressive then `unfold_locales' and does not

unfold predicates to assumptions.

* Isar/locales: the order in which locale fragments are accumulated

has changed.  This enables to override declarations from fragments due

to interpretations -- for example, unwanted simp rules.

* Isar/locales: interpretation in theories and proof contexts has been

extended.  One may now specify (and prove) equations, which are

unfolded in interpreted theorems.  This is useful for replacing

defined concepts (constants depending on locale parameters) by

concepts already existing in the target context.  Example:

  interpretation partial_order ["op <= :: [int, int] => bool"]

    where "partial_order.less (op <=) (x::int) y = (x < y)"

Typically, the constant `partial_order.less' is created by a

definition specification element in the context of locale

partial_order.

* Method "induct": improved internal context management to support

local fixes and defines on-the-fly. Thus explicit meta-level

connectives !!  and ==> are rarely required anymore in inductive goals

(using object-logic connectives for this purpose has been long

obsolete anyway). Common proof patterns are explained in

src/HOL/Induct/Common_Patterns.thy, see also

src/HOL/Isar_examples/Puzzle.thy and src/HOL/Lambda for realistic

examples.

* Method "induct": improved handling of simultaneous goals. Instead of

introducing object-level conjunction, the statement is now split into

several conclusions, while the corresponding symbolic cases are nested

accordingly. INCOMPATIBILITY, proofs need to be structured explicitly,

see src/HOL/Induct/Common_Patterns.thy, for example.

* Method "induct": mutual induction rules are now specified as a list

of rule sharing the same induction cases. HOL packages usually provide

foo_bar.inducts for mutually defined items foo and bar (e.g. inductive

predicates/sets or datatypes). INCOMPATIBILITY, users need to specify

mutual induction rules differently, i.e. like this: