* MW: check uses of Unsynchronized.ref vs. Synchronized.var;

* 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"),

* Eliminate Thy_Info.get_theory eventually: should take theory from ancestory

  within current context.

    cf. e587c45cae0f note in Build_Thydata.thy

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

    ??

* KEStore_Elems: Should we eliminate union_overwrite and use standard namespace merge?

  (Exception: rlss with its special cross-theory merge.)

* What is the purpose of "#numeral" instead of plain numeral?

    ??

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

    present ISAC assumes 2 sessions in the MathEngine, Specify and Interpret, 

    and all Isac_Knowledge is in session Isac.

    So Context.theory_name suffices

* Eliminate mutable Rewrite_Ord.rew_ord' (!?);

    shall be done in connection with cf. e587c45cae0f note in Build_Thydata.thy

* What is the idea behind KEStore_Elems.add_thes? How to do it properly in current Isabelle?

    https://static.miraheze.org/isacwiki/0/04/Isac-docu.pdf distinguishes 

    several kinds of ISAC users, in particular "math author (Mathematik-Autor)" and

    "course designer (Kurs-Designer)". The latter just adds examples which re-use existing

    knowledge designed by the former. KEStore_Elems.add_thes is an interface for the latter.   

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

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

* WN: eliminate global flags like "trace_on", replace Unsynchronized.ref by

    ML \<open>val rewrite_trace = Attrib.setup_config_bool \<^binding>\<open>rewrite_trace\<close> (K false);\<close>

* WN: Avoid Thm.get_name_hint --- somewhat fragile.

    Thm.get_name_hint supports lazyness of students, who do not care about theories

    a theorem is defined in.

    Dropping it, e.g. in "fun revert_sym_rule", breaks tests on Thy_Write.thydata,

    which shall be dropped; see e587c45cae0f note in Build_Thydata.thy.

  + what remains TODO: use Global_Theory.get_thm instead, get theory from References.T

    and push theory through as argument of respective functions.

* 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: eliminate ThmC.numerals_to_Free, done except 1 error:

  + exception TYPE raised by Skip_Proof.make_thm, several inherited errors in tests marked TOODOO.1

  + ? how do algebraic operations on numerals ? Presburger ? simplifier ? hack see

    https://hg.risc.uni-linz.ac.at/wneuper/isa/file/a14022b99b92/src/Tools/isac/ProgLang/evaluate.sml#l210

* WN: DONE cleanup remaining ^^^ in comments (but sometimes it is just ASCII art), partially;

      Left ^^^ in doc-isac (old master-theses, etc: "x^^^#2 + #8" ... # are left, too)

      Left "ASCII art" in case of indicating comments pointing at facts ABOVE.

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

      ???

* WN: reduce the number of TermC.parse*;

  + 0d22a6bf1fc6 was too much for 1 changeset

  + first parse with ctxt in Specify (O_Model.init shall return a context,..) etc

* WN: push suggestions of MW through the whole code

  + e1da148725ed : \<^ML>\<open>...\<close> instead of parentheses

  +