NEWS
author nipkow
Wed Jun 24 13:59:45 1998 +0200 (1998-06-24)
changeset 5077 71043526295f
parent 5075 9a3d48fa28ca
child 5085 8e5a7942fdea
permissions -rw-r--r--
* 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,...].
     1 Isabelle NEWS -- history of user-visible changes
     2 ================================================
     3 
     4 New in this Isabelle version
     5 ----------------------------
     6 
     7 *** General Changes ***
     8 
     9 * new toplevel commands `Goal' and `Goalw' that improve upon `goal'
    10 and `goalw': the theory is no longer needed as an explicit argument -
    11 the current theory is used; assumptions are no longer returned at the
    12 ML-level unless one of them starts with ==> or !!; it is recommended
    13 to convert to these new commands using isatool fixgoal (as usual,
    14 backup your sources first!);
    15 
    16 * Simplifier: Asm_full_simp_tac is now more aggressive.
    17   1. It will sometimes reorient premises if that increases their power to
    18      simplify.
    19   2. It does no longer proceed strictly from left to right but may also
    20      rotate premises to achieve further simplification.
    21   For compatibility reasons there is now Asm_lr_simp_tac which is like the
    22   old Asm_full_simp_tac in that it does not rotate premises.
    23 
    24 * Changed wrapper mechanism for the classical reasoner now allows for
    25 selected deletion of wrappers, by introduction of names for wrapper
    26 functionals.  This implies that addbefore, addSbefore, addaltern, and
    27 addSaltern now take a pair (name, tactic) as argument, and that adding
    28 two tactics with the same name overwrites the first one (emitting a
    29 warning).
    30   type wrapper = (int -> tactic) -> (int -> tactic)
    31   setWrapper, setSWrapper, compWrapper and compSWrapper are replaced by
    32   addWrapper, addSWrapper: claset * (string * wrapper) -> claset
    33   delWrapper, delSWrapper: claset *  string            -> claset
    34   getWrapper is renamed to appWrappers, getSWrapper to appSWrappers;
    35 
    36 * inductive definitions now handle disjunctive premises correctly (HOL
    37 and ZF);
    38 
    39 * new toplevel commands 'thm' and 'thms' for retrieving theorems from
    40 the current theory context;
    41 
    42 * new theory section 'nonterminals';
    43 
    44 * new theory section 'setup';
    45 
    46 
    47 *** HOL ***
    48 
    49 * HOL/record: now includes concrete syntax for record terms (still
    50 lacks important theorems, like surjective pairing and split);
    51 
    52 * new force_tac (and its derivations Force_tac, force): combines
    53 rewriting and classical reasoning (and whatever other tools) similarly
    54 to auto_tac, but is aimed to solve the given subgoal totally;
    55 
    56 * added option_map_eq_Some to simpset() and claset()
    57 
    58 * New directory HOL/UNITY: Chandy and Misra's UNITY formalism
    59 
    60 * New theory HOL/Update of function updates:
    61   f(a:=b) == %x. if x=a then b else f x
    62   May also be iterated as in f(a:=b,c:=d,...).
    63 
    64 * HOL/List: new function list_update written xs[i:=v] that updates the i-th
    65   list position. May also be iterated as in xs[i:=a,j:=b,...].
    66 
    67 * split_all_tac is now much faster and fails if there is nothing to
    68 split.  Existing (fragile) proofs may require adaption because the
    69 order and the names of the automatically generated variables have
    70 changed.  split_all_tac has moved within claset() from usafe wrappers
    71 to safe wrappers, which means that !!-bound variables are splitted
    72 much more aggressively, and safe_tac and clarify_tac now split such
    73 variables.  If this splitting is not appropriate, use delSWrapper
    74 "split_all_tac".
    75 
    76 * added disj_not1 = "(~P | Q) = (P --> Q)" to the default simpset;
    77 
    78 * HOL/Arithmetic:
    79   
    80   - removed 'pred' (predecessor) function
    81   - generalized some theorems about n-1
    82   - Many new laws about "div" and "mod"
    83   - New laws about greatest common divisors (see theory ex/Primes)
    84 
    85 * HOL/Relation: renamed the relational operatotr r^-1 "converse"
    86 instead of "inverse";
    87 
    88 * recdef can now declare non-recursive functions, with {} supplied as
    89 the well-founded relation;
    90 
    91 * expand_if, expand_split, expand_sum_case and expand_nat_case are now called
    92   split_if, split_split, split_sum_case and split_nat_case
    93   (to go with add/delsplits).
    94 
    95 * Simplifier:
    96 
    97  -Rewrite rules for case distinctions can now be added permanently to the
    98   default simpset using Addsplits just like Addsimps. They can be removed via
    99   Delsplits just like Delsimps. Lower-case versions are also available.
   100 
   101  -The rule split_if is now part of the default simpset. This means that
   102   the simplifier will eliminate all ocurrences of if-then-else in the
   103   conclusion of a goal. To prevent this, you can either remove split_if
   104   completely from the default simpset by `Delsplits [split_if]' or
   105   remove it in a specific call of the simplifier using
   106   `... delsplits [split_if]'.
   107   You can also add/delete other case splitting rules to/from the default
   108   simpset: every datatype generates suitable rules `split_t_case' and
   109   `split_t_case_asm' (where t is the name of the datatype).
   110 
   111 * new theory Vimage (inverse image of a function, syntax f-``B);
   112 
   113 * many new identities for unions, intersections, set difference, etc.;
   114 
   115 
   116 *** ZF ***
   117 
   118 * in  let x=t in u(x), neither t nor u(x) has to be an FOL term.
   119 
   120 
   121 *** Internal changes ***
   122 
   123 * improved the theory data mechanism to support encapsulation (data
   124 kind name replaced by private Object.kind, acting as authorization
   125 key); new type-safe user interface via functor TheoryDataFun;
   126 
   127 
   128 
   129 New in Isabelle98 (January 1998)
   130 --------------------------------
   131 
   132 *** Overview of INCOMPATIBILITIES (see below for more details) ***
   133 
   134 * changed lexical syntax of terms / types: dots made part of long
   135 identifiers, e.g. "%x.x" no longer possible, should be "%x. x";
   136 
   137 * simpset (and claset) reference variable replaced by functions
   138 simpset / simpset_ref;
   139 
   140 * no longer supports theory aliases (via merge) and non-trivial
   141 implicit merge of thms' signatures;
   142 
   143 * most internal names of constants changed due to qualified names;
   144 
   145 * changed Pure/Sequence interface (see Pure/seq.ML);
   146 
   147 
   148 *** General Changes ***
   149 
   150 * hierachically structured name spaces (for consts, types, axms, thms
   151 etc.); new lexical class 'longid' (e.g. Foo.bar.x) may render much of
   152 old input syntactically incorrect (e.g. "%x.x"); COMPATIBILITY:
   153 isatool fixdots ensures space after dots (e.g. "%x. x"); set
   154 long_names for fully qualified output names; NOTE: ML programs
   155 (special tactics, packages etc.) referring to internal names may have
   156 to be adapted to cope with fully qualified names; in case of severe
   157 backward campatibility problems try setting 'global_names' at compile
   158 time to have enrything declared within a flat name space; one may also
   159 fine tune name declarations in theories via the 'global' and 'local'
   160 section;
   161 
   162 * reimplemented the implicit simpset and claset using the new anytype
   163 data filed in signatures; references simpset:simpset ref etc. are
   164 replaced by functions simpset:unit->simpset and
   165 simpset_ref:unit->simpset ref; COMPATIBILITY: use isatool fixclasimp
   166 to patch your ML files accordingly;
   167 
   168 * HTML output now includes theory graph data for display with Java
   169 applet or isatool browser; data generated automatically via isatool
   170 usedir (see -i option, ISABELLE_USEDIR_OPTIONS);
   171 
   172 * defs may now be conditional; improved rewrite_goals_tac to handle
   173 conditional equations;
   174 
   175 * defs now admits additional type arguments, using TYPE('a) syntax;
   176 
   177 * theory aliases via merge (e.g. M=A+B+C) no longer supported, always
   178 creates a new theory node; implicit merge of thms' signatures is
   179 restricted to 'trivial' ones; COMPATIBILITY: one may have to use
   180 transfer:theory->thm->thm in (rare) cases;
   181 
   182 * improved handling of draft signatures / theories; draft thms (and
   183 ctyps, cterms) are automatically promoted to real ones;
   184 
   185 * slightly changed interfaces for oracles: admit many per theory, named
   186 (e.g. oracle foo = mlfun), additional name argument for invoke_oracle;
   187 
   188 * print_goals: optional output of const types (set show_consts and
   189 show_types);
   190 
   191 * improved output of warnings (###) and errors (***);
   192 
   193 * subgoal_tac displays a warning if the new subgoal has type variables;
   194 
   195 * removed old README and Makefiles;
   196 
   197 * replaced print_goals_ref hook by print_current_goals_fn and result_error_fn;
   198 
   199 * removed obsolete init_pps and init_database;
   200 
   201 * deleted the obsolete tactical STATE, which was declared by
   202     fun STATE tacfun st = tacfun st st;
   203 
   204 * cd and use now support path variables, e.g. $ISABELLE_HOME, or ~
   205 (which abbreviates $HOME);
   206 
   207 * changed Pure/Sequence interface (see Pure/seq.ML); COMPATIBILITY:
   208 use isatool fixseq to adapt your ML programs (this works for fully
   209 qualified references to the Sequence structure only!);
   210 
   211 * use_thy no longer requires writable current directory; it always
   212 reloads .ML *and* .thy file, if either one is out of date;
   213 
   214 
   215 *** Classical Reasoner ***
   216 
   217 * Clarify_tac, clarify_tac, clarify_step_tac, Clarify_step_tac: new
   218 tactics that use classical reasoning to simplify a subgoal without
   219 splitting it into several subgoals;
   220 
   221 * Safe_tac: like safe_tac but uses the default claset;
   222 
   223 
   224 *** Simplifier ***
   225 
   226 * added simplification meta rules:
   227     (asm_)(full_)simplify: simpset -> thm -> thm;
   228 
   229 * simplifier.ML no longer part of Pure -- has to be loaded by object
   230 logics (again);
   231 
   232 * added prems argument to simplification procedures;
   233 
   234 * HOL, FOL, ZF: added infix function `addsplits':
   235   instead of `<simpset> setloop (split_tac <thms>)'
   236   you can simply write `<simpset> addsplits <thms>'
   237 
   238 
   239 *** Syntax ***
   240 
   241 * TYPE('a) syntax for type reflection terms;
   242 
   243 * no longer handles consts with name "" -- declare as 'syntax' instead;
   244 
   245 * pretty printer: changed order of mixfix annotation preference (again!);
   246 
   247 * Pure: fixed idt/idts vs. pttrn/pttrns syntactic categories;
   248 
   249 
   250 *** HOL ***
   251 
   252 * HOL: there is a new splitter `split_asm_tac' that can be used e.g. 
   253   with `addloop' of the simplifier to faciliate case splitting in premises.
   254 
   255 * HOL/TLA: Stephan Merz's formalization of Lamport's Temporal Logic of Actions;
   256 
   257 * HOL/Auth: new protocol proofs including some for the Internet
   258   protocol TLS;
   259 
   260 * HOL/Map: new theory of `maps' a la VDM;
   261 
   262 * HOL/simplifier: simplification procedures nat_cancel_sums for
   263 cancelling out common nat summands from =, <, <= (in)equalities, or
   264 differences; simplification procedures nat_cancel_factor for
   265 cancelling common factor from =, <, <= (in)equalities over natural
   266 sums; nat_cancel contains both kinds of procedures, it is installed by
   267 default in Arith.thy -- this COULD MAKE EXISTING PROOFS FAIL;
   268 
   269 * HOL/simplifier: terms of the form
   270   `? x. P1(x) & ... & Pn(x) & x=t & Q1(x) & ... Qn(x)'  (or t=x)
   271   are rewritten to
   272   `P1(t) & ... & Pn(t) & Q1(t) & ... Qn(t)',
   273   and those of the form
   274   `! x. P1(x) & ... & Pn(x) & x=t & Q1(x) & ... Qn(x) --> R(x)'  (or t=x)
   275   are rewritten to
   276   `P1(t) & ... & Pn(t) & Q1(t) & ... Qn(t) --> R(t)',
   277 
   278 * HOL/datatype
   279   Each datatype `t' now comes with a theorem `split_t_case' of the form
   280 
   281   P(t_case f1 ... fn x) =
   282      ( (!y1 ... ym1. x = C1 y1 ... ym1 --> P(f1 y1 ... ym1)) &
   283         ...
   284        (!y1 ... ymn. x = Cn y1 ... ymn --> P(f1 y1 ... ymn))
   285      )
   286 
   287   and a theorem `split_t_case_asm' of the form
   288 
   289   P(t_case f1 ... fn x) =
   290     ~( (? y1 ... ym1. x = C1 y1 ... ym1 & ~P(f1 y1 ... ym1)) |
   291         ...
   292        (? y1 ... ymn. x = Cn y1 ... ymn & ~P(f1 y1 ... ymn))
   293      )
   294   which can be added to a simpset via `addsplits'. The existing theorems
   295   expand_list_case and expand_option_case have been renamed to
   296   split_list_case and split_option_case.
   297 
   298 * HOL/Arithmetic:
   299   - `pred n' is automatically converted to `n-1'.
   300     Users are strongly encouraged not to use `pred' any longer,
   301     because it will disappear altogether at some point.
   302   - Users are strongly encouraged to write "0 < n" rather than
   303     "n ~= 0". Theorems and proof tools have been modified towards this
   304     `standard'.
   305 
   306 * HOL/Lists:
   307   the function "set_of_list" has been renamed "set" (and its theorems too);
   308   the function "nth" now takes its arguments in the reverse order and
   309   has acquired the infix notation "!" as in "xs!n".
   310 
   311 * HOL/Set: UNIV is now a constant and is no longer translated to Compl{};
   312 
   313 * HOL/Set: The operator (UN x.B x) now abbreviates (UN x:UNIV. B x) and its
   314   specialist theorems (like UN1_I) are gone.  Similarly for (INT x.B x);
   315 
   316 * HOL/record: extensible records with schematic structural subtyping
   317 (single inheritance); EXPERIMENTAL version demonstrating the encoding,
   318 still lacks various theorems and concrete record syntax;
   319 
   320 
   321 *** HOLCF ***
   322 
   323 * removed "axioms" and "generated by" sections;
   324 
   325 * replaced "ops" section by extended "consts" section, which is capable of
   326   handling the continuous function space "->" directly;
   327 
   328 * domain package:
   329   . proves theorems immediately and stores them in the theory,
   330   . creates hierachical name space,
   331   . now uses normal mixfix annotations (instead of cinfix...),
   332   . minor changes to some names and values (for consistency),
   333   . e.g. cases -> casedist, dists_eq -> dist_eqs, [take_lemma] -> take_lemmas,
   334   . separator between mutual domain defs: changed "," to "and",
   335   . improved handling of sort constraints;  now they have to
   336     appear on the left-hand side of the equations only;
   337 
   338 * fixed LAM <x,y,zs>.b syntax;
   339 
   340 * added extended adm_tac to simplifier in HOLCF -- can now discharge
   341 adm (%x. P (t x)), where P is chainfinite and t continuous;
   342 
   343 
   344 *** FOL and ZF ***
   345 
   346 * FOL: there is a new splitter `split_asm_tac' that can be used e.g. 
   347   with `addloop' of the simplifier to faciliate case splitting in premises.
   348 
   349 * qed_spec_mp, qed_goal_spec_mp, qed_goalw_spec_mp are available, as
   350 in HOL, they strip ALL and --> from proved theorems;
   351 
   352 
   353 
   354 New in Isabelle94-8 (May 1997)
   355 ------------------------------
   356 
   357 *** General Changes ***
   358 
   359 * new utilities to build / run / maintain Isabelle etc. (in parts
   360 still somewhat experimental); old Makefiles etc. still functional;
   361 
   362 * new 'Isabelle System Manual';
   363 
   364 * INSTALL text, together with ./configure and ./build scripts;
   365 
   366 * reimplemented type inference for greater efficiency, better error
   367 messages and clean internal interface;
   368 
   369 * prlim command for dealing with lots of subgoals (an easier way of
   370 setting goals_limit);
   371 
   372 
   373 *** Syntax ***
   374 
   375 * supports alternative (named) syntax tables (parser and pretty
   376 printer); internal interface is provided by add_modesyntax(_i);
   377 
   378 * Pure, FOL, ZF, HOL, HOLCF now support symbolic input and output; to
   379 be used in conjunction with the Isabelle symbol font; uses the
   380 "symbols" syntax table;
   381 
   382 * added token_translation interface (may translate name tokens in
   383 arbitrary ways, dependent on their type (free, bound, tfree, ...) and
   384 the current print_mode); IMPORTANT: user print translation functions
   385 are responsible for marking newly introduced bounds
   386 (Syntax.mark_boundT);
   387 
   388 * token translations for modes "xterm" and "xterm_color" that display
   389 names in bold, underline etc. or colors (which requires a color
   390 version of xterm);
   391 
   392 * infixes may now be declared with names independent of their syntax;
   393 
   394 * added typed_print_translation (like print_translation, but may
   395 access type of constant);
   396 
   397 
   398 *** Classical Reasoner ***
   399 
   400 Blast_tac: a new tactic!  It is often more powerful than fast_tac, but has
   401 some limitations.  Blast_tac...
   402   + ignores addss, addbefore, addafter; this restriction is intrinsic
   403   + ignores elimination rules that don't have the correct format
   404 	(the conclusion MUST be a formula variable)
   405   + ignores types, which can make HOL proofs fail
   406   + rules must not require higher-order unification, e.g. apply_type in ZF
   407     [message "Function Var's argument not a bound variable" relates to this]
   408   + its proof strategy is more general but can actually be slower
   409 
   410 * substitution with equality assumptions no longer permutes other
   411 assumptions;
   412 
   413 * minor changes in semantics of addafter (now called addaltern); renamed
   414 setwrapper to setWrapper and compwrapper to compWrapper; added safe wrapper
   415 (and access functions for it);
   416 
   417 * improved combination of classical reasoner and simplifier: 
   418   + functions for handling clasimpsets
   419   + improvement of addss: now the simplifier is called _after_ the
   420     safe steps.
   421   + safe variant of addss called addSss: uses safe simplifications
   422     _during_ the safe steps. It is more complete as it allows multiple 
   423     instantiations of unknowns (e.g. with slow_tac).
   424 
   425 *** Simplifier ***
   426 
   427 * added interface for simplification procedures (functions that
   428 produce *proven* rewrite rules on the fly, depending on current
   429 redex);
   430 
   431 * ordering on terms as parameter (used for ordered rewriting);
   432 
   433 * new functions delcongs, deleqcongs, and Delcongs. richer rep_ss;
   434 
   435 * the solver is now split into a safe and an unsafe part.
   436 This should be invisible for the normal user, except that the
   437 functions setsolver and addsolver have been renamed to setSolver and
   438 addSolver; added safe_asm_full_simp_tac;
   439 
   440 
   441 *** HOL ***
   442 
   443 * a generic induction tactic `induct_tac' which works for all datatypes and
   444 also for type `nat';
   445 
   446 * a generic case distinction tactic `exhaust_tac' which works for all
   447 datatypes and also for type `nat';
   448 
   449 * each datatype comes with a function `size';
   450 
   451 * patterns in case expressions allow tuple patterns as arguments to
   452 constructors, for example `case x of [] => ... | (x,y,z)#ps => ...';
   453 
   454 * primrec now also works with type nat;
   455 
   456 * recdef: a new declaration form, allows general recursive functions to be
   457 defined in theory files.  See HOL/ex/Fib, HOL/ex/Primes, HOL/Subst/Unify.
   458 
   459 * the constant for negation has been renamed from "not" to "Not" to
   460 harmonize with FOL, ZF, LK, etc.;
   461 
   462 * HOL/ex/LFilter theory of a corecursive "filter" functional for
   463 infinite lists;
   464 
   465 * HOL/Modelcheck demonstrates invocation of model checker oracle;
   466 
   467 * HOL/ex/Ring.thy declares cring_simp, which solves equational
   468 problems in commutative rings, using axiomatic type classes for + and *;
   469 
   470 * more examples in HOL/MiniML and HOL/Auth;
   471 
   472 * more default rewrite rules for quantifiers, union/intersection;
   473 
   474 * a new constant `arbitrary == @x.False';
   475 
   476 * HOLCF/IOA replaces old HOL/IOA;
   477 
   478 * HOLCF changes: derived all rules and arities 
   479   + axiomatic type classes instead of classes 
   480   + typedef instead of faking type definitions
   481   + eliminated the internal constants less_fun, less_cfun, UU_fun, UU_cfun etc.
   482   + new axclasses cpo, chfin, flat with flat < chfin < pcpo < cpo < po
   483   + eliminated the types void, one, tr
   484   + use unit lift and bool lift (with translations) instead of one and tr
   485   + eliminated blift from Lift3.thy (use Def instead of blift)
   486   all eliminated rules are derived as theorems --> no visible changes ;
   487 
   488 
   489 *** ZF ***
   490 
   491 * ZF now has Fast_tac, Simp_tac and Auto_tac.  Union_iff is a now a default
   492 rewrite rule; this may affect some proofs.  eq_cs is gone but can be put back
   493 as ZF_cs addSIs [equalityI];
   494 
   495 
   496 
   497 New in Isabelle94-7 (November 96)
   498 ---------------------------------
   499 
   500 * allowing negative levels (as offsets) in prlev and choplev;
   501 
   502 * super-linear speedup for large simplifications;
   503 
   504 * FOL, ZF and HOL now use miniscoping: rewriting pushes
   505 quantifications in as far as possible (COULD MAKE EXISTING PROOFS
   506 FAIL); can suppress it using the command Delsimps (ex_simps @
   507 all_simps); De Morgan laws are also now included, by default;
   508 
   509 * improved printing of ==>  :  ~:
   510 
   511 * new object-logic "Sequents" adds linear logic, while replacing LK
   512 and Modal (thanks to Sara Kalvala);
   513 
   514 * HOL/Auth: correctness proofs for authentication protocols;
   515 
   516 * HOL: new auto_tac combines rewriting and classical reasoning (many
   517 examples on HOL/Auth);
   518 
   519 * HOL: new command AddIffs for declaring theorems of the form P=Q to
   520 the rewriter and classical reasoner simultaneously;
   521 
   522 * function uresult no longer returns theorems in "standard" format;
   523 regain previous version by: val uresult = standard o uresult;
   524 
   525 
   526 
   527 New in Isabelle94-6
   528 -------------------
   529 
   530 * oracles -- these establish an interface between Isabelle and trusted
   531 external reasoners, which may deliver results as theorems;
   532 
   533 * proof objects (in particular record all uses of oracles);
   534 
   535 * Simp_tac, Fast_tac, etc. that refer to implicit simpset / claset;
   536 
   537 * "constdefs" section in theory files;
   538 
   539 * "primrec" section (HOL) no longer requires names;
   540 
   541 * internal type "tactic" now simply "thm -> thm Sequence.seq";
   542 
   543 
   544 
   545 New in Isabelle94-5
   546 -------------------
   547 
   548 * reduced space requirements;
   549 
   550 * automatic HTML generation from theories;
   551 
   552 * theory files no longer require "..." (quotes) around most types;
   553 
   554 * new examples, including two proofs of the Church-Rosser theorem;
   555 
   556 * non-curried (1994) version of HOL is no longer distributed;
   557 
   558 
   559 
   560 New in Isabelle94-4
   561 -------------------
   562 
   563 * greatly reduced space requirements;
   564 
   565 * theory files (.thy) no longer require \...\ escapes at line breaks;
   566 
   567 * searchable theorem database (see the section "Retrieving theorems" on 
   568 page 8 of the Reference Manual);
   569 
   570 * new examples, including Grabczewski's monumental case study of the
   571 Axiom of Choice;
   572 
   573 * The previous version of HOL renamed to Old_HOL;
   574 
   575 * The new version of HOL (previously called CHOL) uses a curried syntax 
   576 for functions.  Application looks like f a b instead of f(a,b);
   577 
   578 * Mutually recursive inductive definitions finally work in HOL;
   579 
   580 * In ZF, pattern-matching on tuples is now available in all abstractions and
   581 translates to the operator "split";
   582 
   583 
   584 
   585 New in Isabelle94-3
   586 -------------------
   587 
   588 * new infix operator, addss, allowing the classical reasoner to 
   589 perform simplification at each step of its search.  Example:
   590 	fast_tac (cs addss ss)
   591 
   592 * a new logic, CHOL, the same as HOL, but with a curried syntax 
   593 for functions.  Application looks like f a b instead of f(a,b).  Also pairs 
   594 look like (a,b) instead of <a,b>;
   595 
   596 * PLEASE NOTE: CHOL will eventually replace HOL!
   597 
   598 * In CHOL, pattern-matching on tuples is now available in all abstractions.
   599 It translates to the operator "split".  A new theory of integers is available;
   600 
   601 * In ZF, integer numerals now denote two's-complement binary integers.
   602 Arithmetic operations can be performed by rewriting.  See ZF/ex/Bin.ML;
   603 
   604 * Many new examples: I/O automata, Church-Rosser theorem, equivalents 
   605 of the Axiom of Choice;
   606 
   607 
   608 
   609 New in Isabelle94-2
   610 -------------------
   611 
   612 * Significantly faster resolution;  
   613 
   614 * the different sections in a .thy file can now be mixed and repeated
   615 freely;
   616 
   617 * Database of theorems for FOL, HOL and ZF.  New
   618 commands including qed, qed_goal and bind_thm store theorems in the database.
   619 
   620 * Simple database queries: return a named theorem (get_thm) or all theorems of
   621 a given theory (thms_of), or find out what theory a theorem was proved in
   622 (theory_of_thm);
   623 
   624 * Bugs fixed in the inductive definition and datatype packages;
   625 
   626 * The classical reasoner provides deepen_tac and depth_tac, making FOL_dup_cs
   627 and HOL_dup_cs obsolete;
   628 
   629 * Syntactic ambiguities caused by the new treatment of syntax in Isabelle94-1
   630 have been removed;
   631 
   632 * Simpler definition of function space in ZF;
   633 
   634 * new results about cardinal and ordinal arithmetic in ZF;
   635 
   636 * 'subtype' facility in HOL for introducing new types as subsets of existing
   637 types;
   638 
   639 
   640 $Id$