NEWS

Adapted to new datatype package.

Isabelle NEWS -- history of user-visible changes
================================================

New in this Isabelle version
----------------------------

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

* several changes of proof tools (see next section);

* HOL/datatype:
  - Theories using datatypes must now have Datatype.thy as an
    ancestor.
  - The specific <typename>.induct_tac no longer exists - use the
    generic induct_tac instead.
  - natE has been renamed to nat.exhaustion - use exhaust_tac
    instead of res_inst_tac ... natE. Note that the variable
    names in nat.exhaustion 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 are no longer ignored by the package,
    some datatype definitions may have to be annotated with
    explicit sort constraints.
  - Primrec definitions no longer require function name and type
    of recursive argument.
  Use isatool fixdatatype to adapt your theories and proof scripts
  to the new package (as usual, backup your sources first!).

* HOL/inductive requires Inductive.thy as an ancestor; `inj_onto' is
now called `inj_on' (which makes more sense);

* HOL/Relation: renamed the relational operator r^-1 to 'converse'
from 'inverse' (for compatibility with ZF and some literature);


*** Proof tools ***

* Simplifier: 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.

* 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;

* HOL/split_all_tac is now much faster and fails if there is nothing
to split.  Existing (fragile) 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".

* 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.

 - 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 toplevel 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 (as
usual, backup your sources first!);

* new toplevel commands 'thm' and 'thms' for retrieving theorems from
the current theory context, and 'theory' to lookup stored theories;

* 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;


*** HOL ***

* HOL/datatype package reorganized and 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

* reorganized the main HOL image: HOL/Integ and String loaded by
default; theory Main includes everything;

* added option_map_eq_Some to the default simpset 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/record package: now includes concrete syntax for record types,
terms, updates; still lacks important theorems, like surjective
pairing and split;

* 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 component "elims" of the structure created by the package contains
an elimination rule for each of the recursive sets; requires
Inductive.thy as an ancestor; component "mutual_induct" no longer
exists - the induction rule is always contained in "induct"; inductive
definitions now handle disjunctive premises correctly (also ZF);

* HOL/recdef can now declare non-recursive functions, with {} supplied as
the well-founded relation;

* 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,...].

* 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/Set: added the predicate "disjoint A B" that stands for "A <= Compl B".
  This is much better than "A Int B = {}" for Fast/Blast_tac.

* directory HOL/Real: a construction of the reals using Dedekind cuts
(not included by default);

* directory HOL/UNITY: Chandy and Misra's UNITY formalism;

* 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]


*** ZF ***

* theory Main includes everything;

* 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]

* case_tac provided for compatibility with HOL
    (like the old excluded_middle_tac, but with subgoals swapped)


*** Internal programming interfaces ***

* removed global_names compatibility flag -- all theory declarations
are qualified by default;

* 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;

* module Pure/Syntax now offers quote / antiquote translation
functions (useful for Hoare logic etc. with implicit dependencies);

* Simplifier now offers conversions (asm_)(full_)rewrite: simpset ->
cterm -> thm;

* Pure: several new basic modules made available for general use, see
also src/Pure/README;

* new tactical CHANGED_GOAL for checking that a tactic modifies a
subgoal;



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)

* a new logic, CHOL, the same as HOL, but with a curried syntax 
for functions.  Application looks like f a b instead of f(a,b).  Also pairs 
look like (a,b) instead of <a,b>;

* PLEASE NOTE: CHOL will eventually replace HOL!

* In CHOL, pattern-matching on tuples is now available in all abstractions.
It translates to the operator "split".  A new theory of integers is available;

* In ZF, integer numerals now denote two's-complement binary integers.
Arithmetic operations can be performed by rewriting.  See ZF/ex/Bin.ML;

* Many new examples: I/O automata, Church-Rosser theorem, equivalents 
of the Axiom of Choice;



New in Isabelle94-2
-------------------

* Significantly faster resolution;  

* the different sections in a .thy file can now be mixed and repeated
freely;

* Database of theorems for FOL, HOL and ZF.  New
commands including qed, qed_goal and bind_thm store theorems in the database.

* Simple database queries: return a named theorem (get_thm) or all theorems of
a given theory (thms_of), or find out what theory a theorem was proved in
(theory_of_thm);

* Bugs fixed in the inductive definition and datatype packages;

* The classical reasoner provides deepen_tac and depth_tac, making FOL_dup_cs
and HOL_dup_cs obsolete;

* Syntactic ambiguities caused by the new treatment of syntax in Isabelle94-1
have been removed;

* Simpler definition of function space in ZF;

* new results about cardinal and ordinal arithmetic in ZF;

* 'subtype' facility in HOL for introducing new types as subsets of existing
types;


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