* MW: implement ML toplevel spans in official Isabelle, e.g.

  with separator \<^medskip> and some tool support for automated

  update (in "isabelle update" and/or PIDE);

* MW?: rename *.sml to *.ML, potentially with tool support;

* MW: clarify/eliminate Isabelle/Scala add-ons (presently unused)

    diff -r /home/makarius/isabelle/repos-Isabelle2021/src/Pure/build-jars ./src/Pure/build-jars

    11a12

    >   src/Tools/isac/BridgeJEdit/isac.scala

    diff -r /home/makarius/isabelle/repos-Isabelle2021/src/Pure/Tools/scala_project.scala ./src/Pure/Tools/scala_project.scala

    76a77

    >       "src/Tools/isac/etc" -> Path.explode("isabelle.isac"),

* MW: Skip_Proof.make_thm: theory -> term -> thm        ? could now change signature to

                         : Proof.context -> term -> thm

* MW: Make $ISABELLE_ISAC_TEST work without sessions (please synchronise with WN)

***** some items for discussion

* Clarify symmetric rule: Thm.apply_attribute Calculation.symmetric thm context (!?);

    ??

* "fun pr_ord" is not required if used with @{make_string}, @{print}, @{print tracing};

    takes only static arguments ----------------^^^^^^^^^^^^^^, not value of "hd_ord (f, g)"

    ? are there better approximations to old output of (*1*) than with (*2*)

    (*1*)val _ = tracing ("hd_ord (f, g)      = " ^ ((pr_ord o hd_ord) (f, g)) );

    (*2*)val _ = @{print tracing}{a = "hd_ord (f, g)      = ", z = hd_ord (f, g)}(**)

***** for the few items below WN asks MW for help

* postpone: ?How accomplish two user-requirements by Outer_Syntax.command \<^command_keyword>\<open>Example\<close>

   (1) start a Calculation with a CAS_Cmd

   (2) start an Example from scratch, i.e. with (Formalize.empty, References.empty)

   Proposals for a solution are in test/../Test_VSCode_Example.thy

   in subsubsection ‹Start Example with a CAS_Cmd›

***** priority of WN items is top down, most urgent/simple on top

* WN: eliminate multiple get_ctxt in Solve_Step, Ctree

* WN: shift code from libraryC.sml to designated destination (ThyC, etc)

* WN: Know_Store.get_thes, add_thes still required for Error_Patterns, we want to eliminate thes:

    (1) Error_Pattern.T are already stored by MethodC -- place them in respective thys

    (2) Error_Pattern.fill_in stored with thm (in thes): instead introduce new Thy_Data for them.

        adapt Know_Store.insert_fillpats for that purpose.

    cf. e587c45cae0f note in Build_Thydata.thy

* WN: rename type Rule.rule -> Rule.T

* WN: Sub_Problem.tac_from_prog: use ctxt from pt

* WN: in subst_adapt_to_type should ''bdv''(string) handled by Varialbe.declare_constraints

      ?why is "x" not already typed correctly (by reading strings from Formalise)?)

* WN: replace tools derived from get_thes/add_thes by tools derived from current ctxt

* WN: improve naming in refine.sml, m-match.sml

* WN: all UnparseC with Proof.context, cleanup unparseC.sml and calls

* WN: all Subst with Proof.context, cleanup unparseC.sml and calls

* WN: review Prog_Tac:

      (*+isa==isa2*)@{term "Substitution []"};               (*Free ("Subproblem",.. ALSO Subproblem, ?!*)

      (*+isa==isa2*)@{term "Rewrite_Set ''norm_Rational''"}; (*Const ("Prog_Tac.Rewrite_Set",..*)

* WN: Specify/formalise.sml is in BaseDefinitions/ AND Specify/  DELETE ONE VERSION

* WN: Step_Specify.initialise: remove hdl in return-value, replace Step_Specify.nxt_specify_init_calc

      ? which uses initialise !?

* WN: ? unify "no_met" with "empty_meth_id" from References.empty ?

* WN: proper ML antiquotations for "Tactical.Try" etc. --- be careful about unclear situations,

  e.g. "Tactical.Try" vs. "Lucas_Interpreter.Try";

* WN: ? Rational.Cancel_p; extend use of \<^theory> to \<^theory_context>

* WN: Check/clarify Context.theory_name vs. Context.theory_long_name.

    Context.theory_name seems to suffice after elimination of sessions.

* WN: more direct logical foundations wrt. Isabelle/HOL, eliminate many axiomatizations

    - quite often "axiomatization ..." can be turned into "lemma ... by auto"

      without further ado;

    - sometimes this requires to use more specific types / type classes;

    - sometimes this requires to use proper definitional mechanisms (e.g. 'primrec', 'fun');

    - a few "hard" cases will remain, to be reconsidered eventually (e.g. differentiation);

* WN: rename Pos.* -- Pos.ints, Pos.spec, Pos.empty, Pos.ints_empty

* WN: redesign transition from Specification to Solution: how relate 

    - Formalise.model with variants (e.g. VSCode_Example)

      reconsider separation of variants F_I, F_II, see MAWEN paper

    - !?! I_Model of MethodC          (fairly free sequence, dependent on Formalise.model)

    - !?! formal arguments of program (fixed sequence)

* WN: avoid too many uses of "structure Data = Theory_Data", instead use approx. 1 data slot

  per ML module, with type T = ... record or tuple (e.g. see @{apply} ML antiquotation)

* WN: rename *.sml to *.ML, potentially with tool support by MW;

* WN: rename src/Tools/isac/ to main/ (or something else);