NEWS
author nipkow
Wed Jun 17 12:44:02 1998 +0200 (1998-06-17)
changeset 5044 59808d00ea8d
parent 5008 6f56d9650ee9
child 5046 de5eacb7361a
permissions -rw-r--r--
Goal and Goalw
     1 Isabelle NEWS -- history of user-visible changes
     2 ================================================
     3 
     4 New in this Isabelle version
     5 ----------------------------
     6 
     7 *** General Changes ***
     8 
     9 * Simplifier:
    10 
    11  -Asm_full_simp_tac is now more aggressive:
    12   1. It will sometimes reorient premises if that increases their power to
    13      simplify.
    14   2. It does no longer proceed strictly from left to right but may also
    15      rotate premises to achieve further simplification.
    16   For compatibility reasons there is now Asm_lr_simp_tac which is like the
    17   old Asm_full_simp_tac in that it does not rotate premises.
    18 
    19 * Changed wrapper mechanism for the classical reasoner now allows for
    20 selected deletion of wrappers, by introduction of names for wrapper
    21 functionals.  This implies that addbefore, addSbefore, addaltern, and
    22 addSaltern now take a pair (name, tactic) as argument, and that adding
    23 two tactics with the same name overwrites the first one (emitting a
    24 warning).
    25   type wrapper = (int -> tactic) -> (int -> tactic)
    26   setWrapper, setSWrapper, compWrapper and compSWrapper are replaced by
    27   addWrapper, addSWrapper: claset * (string * wrapper) -> claset
    28   delWrapper, delSWrapper: claset *  string            -> claset
    29   getWrapper is renamed to appWrappers, getSWrapper to appSWrappers;
    30 
    31 * new toplevel commands `Goal' and `Goalw' that improve upon `goal' and
    32 `goalw': the theory is no longer needed as an explicit argument - the current
    33 theory is used; assumptions are no longer returned at the ML-level unless one
    34 of them starts with ==> or !!. It is recommended to convert to these new
    35 commands.
    36 
    37 * inductive definitions now handle disjunctive premises correctly (HOL
    38 and ZF);
    39 
    40 * new toplevel commands 'thm' and 'thms' for retrieving theorems from
    41 the current theory context;
    42 
    43 * new theory section 'nonterminals';
    44 
    45 * new theory section 'setup';
    46 
    47 
    48 *** HOL ***
    49 
    50 * HOL/record: now includes concrete syntax for record terms (still
    51 lacks important theorems, like surjective pairing and split);
    52 
    53 * new force_tac (and its derivations Force_tac, force): combines
    54 rewriting and classical reasoning (and whatever other tools) similarly
    55 to auto_tac, but is aimed to solve the given subgoal totally;
    56 
    57 * added option_map_eq_Some to simpset() and claset()
    58 
    59 * New theory HOL/Update of function updates:
    60   f[a:=b] == %x. if x=a then b else f x
    61 
    62 * New directory HOL/UNITY: Chandy and Misra's UNITY formalism
    63 
    64 * split_all_tac is now much faster and fails if there is nothing to
    65 split.  Existing (fragile) proofs may require adaption because the
    66 order and the names of the automatically generated variables have
    67 changed.  split_all_tac has moved within claset() from usafe wrappers
    68 to safe wrappers, which means that !!-bound variables are splitted
    69 much more aggressively, and safe_tac and clarify_tac now split such
    70 variables.  If this splitting is not appropriate, use delSWrapper
    71 "split_all_tac".
    72 
    73 * added disj_not1 = "(~P | Q) = (P --> Q)" to the default simpset;
    74 
    75 * HOL/Arithmetic:
    76   
    77   - removed 'pred' (predecessor) function
    78   - generalized some theorems about n-1
    79   - Many new laws about "div" and "mod"
    80   - New laws about greatest common divisors (see theory ex/Primes)
    81 
    82 * HOL/Relation: renamed the relational operatotr r^-1 "converse"
    83 instead of "inverse";
    84 
    85 * recdef can now declare non-recursive functions, with {} supplied as
    86 the well-founded relation;
    87 
    88 * expand_if, expand_split, expand_sum_case and expand_nat_case are now called
    89   split_if, split_split, split_sum_case and split_nat_case
    90   (to go with add/delsplits).
    91 
    92 * Simplifier:
    93 
    94  -Rewrite rules for case distinctions can now be added permanently to the
    95   default simpset using Addsplits just like Addsimps. They can be removed via
    96   Delsplits just like Delsimps. Lower-case versions are also available.
    97 
    98  -The rule split_if is now part of the default simpset. This means that
    99   the simplifier will eliminate all ocurrences of if-then-else in the
   100   conclusion of a goal. To prevent this, you can either remove split_if
   101   completely from the default simpset by `Delsplits [split_if]' or
   102   remove it in a specific call of the simplifier using
   103   `... delsplits [split_if]'.
   104   You can also add/delete other case splitting rules to/from the default
   105   simpset: every datatype generates suitable rules `split_t_case' and
   106   `split_t_case_asm' (where t is the name of the datatype).
   107 
   108 * new theory Vimage (inverse image of a function, syntax f-``B);
   109 
   110 * many new identities for unions, intersections, set difference, etc.;
   111 
   112 
   113 *** ZF ***
   114 
   115 * in  let x=t in u(x), neither t nor u(x) has to be an FOL term.
   116 
   117 
   118 *** Internal changes ***
   119 
   120 * improved the theory data mechanism to support encapsulation (data
   121 kind name replaced by private Object.kind, acting as authorization
   122 key); new type-safe user interface via functor TheoryDataFun;
   123 
   124 
   125 
   126 New in Isabelle98 (January 1998)
   127 --------------------------------
   128 
   129 *** Overview of INCOMPATIBILITIES (see below for more details) ***
   130 
   131 * changed lexical syntax of terms / types: dots made part of long
   132 identifiers, e.g. "%x.x" no longer possible, should be "%x. x";
   133 
   134 * simpset (and claset) reference variable replaced by functions
   135 simpset / simpset_ref;
   136 
   137 * no longer supports theory aliases (via merge) and non-trivial
   138 implicit merge of thms' signatures;
   139 
   140 * most internal names of constants changed due to qualified names;
   141 
   142 * changed Pure/Sequence interface (see Pure/seq.ML);
   143 
   144 
   145 *** General Changes ***
   146 
   147 * hierachically structured name spaces (for consts, types, axms, thms
   148 etc.); new lexical class 'longid' (e.g. Foo.bar.x) may render much of
   149 old input syntactically incorrect (e.g. "%x.x"); COMPATIBILITY:
   150 isatool fixdots ensures space after dots (e.g. "%x. x"); set
   151 long_names for fully qualified output names; NOTE: ML programs
   152 (special tactics, packages etc.) referring to internal names may have
   153 to be adapted to cope with fully qualified names; in case of severe
   154 backward campatibility problems try setting 'global_names' at compile
   155 time to have enrything declared within a flat name space; one may also
   156 fine tune name declarations in theories via the 'global' and 'local'
   157 section;
   158 
   159 * reimplemented the implicit simpset and claset using the new anytype
   160 data filed in signatures; references simpset:simpset ref etc. are
   161 replaced by functions simpset:unit->simpset and
   162 simpset_ref:unit->simpset ref; COMPATIBILITY: use isatool fixclasimp
   163 to patch your ML files accordingly;
   164 
   165 * HTML output now includes theory graph data for display with Java
   166 applet or isatool browser; data generated automatically via isatool
   167 usedir (see -i option, ISABELLE_USEDIR_OPTIONS);
   168 
   169 * defs may now be conditional; improved rewrite_goals_tac to handle
   170 conditional equations;
   171 
   172 * defs now admits additional type arguments, using TYPE('a) syntax;
   173 
   174 * theory aliases via merge (e.g. M=A+B+C) no longer supported, always
   175 creates a new theory node; implicit merge of thms' signatures is
   176 restricted to 'trivial' ones; COMPATIBILITY: one may have to use
   177 transfer:theory->thm->thm in (rare) cases;
   178 
   179 * improved handling of draft signatures / theories; draft thms (and
   180 ctyps, cterms) are automatically promoted to real ones;
   181 
   182 * slightly changed interfaces for oracles: admit many per theory, named
   183 (e.g. oracle foo = mlfun), additional name argument for invoke_oracle;
   184 
   185 * print_goals: optional output of const types (set show_consts and
   186 show_types);
   187 
   188 * improved output of warnings (###) and errors (***);
   189 
   190 * subgoal_tac displays a warning if the new subgoal has type variables;
   191 
   192 * removed old README and Makefiles;
   193 
   194 * replaced print_goals_ref hook by print_current_goals_fn and result_error_fn;
   195 
   196 * removed obsolete init_pps and init_database;
   197 
   198 * deleted the obsolete tactical STATE, which was declared by
   199     fun STATE tacfun st = tacfun st st;
   200 
   201 * cd and use now support path variables, e.g. $ISABELLE_HOME, or ~
   202 (which abbreviates $HOME);
   203 
   204 * changed Pure/Sequence interface (see Pure/seq.ML); COMPATIBILITY:
   205 use isatool fixseq to adapt your ML programs (this works for fully
   206 qualified references to the Sequence structure only!);
   207 
   208 * use_thy no longer requires writable current directory; it always
   209 reloads .ML *and* .thy file, if either one is out of date;
   210 
   211 
   212 *** Classical Reasoner ***
   213 
   214 * Clarify_tac, clarify_tac, clarify_step_tac, Clarify_step_tac: new
   215 tactics that use classical reasoning to simplify a subgoal without
   216 splitting it into several subgoals;
   217 
   218 * Safe_tac: like safe_tac but uses the default claset;
   219 
   220 
   221 *** Simplifier ***
   222 
   223 * added simplification meta rules:
   224     (asm_)(full_)simplify: simpset -> thm -> thm;
   225 
   226 * simplifier.ML no longer part of Pure -- has to be loaded by object
   227 logics (again);
   228 
   229 * added prems argument to simplification procedures;
   230 
   231 * HOL, FOL, ZF: added infix function `addsplits':
   232   instead of `<simpset> setloop (split_tac <thms>)'
   233   you can simply write `<simpset> addsplits <thms>'
   234 
   235 
   236 *** Syntax ***
   237 
   238 * TYPE('a) syntax for type reflection terms;
   239 
   240 * no longer handles consts with name "" -- declare as 'syntax' instead;
   241 
   242 * pretty printer: changed order of mixfix annotation preference (again!);
   243 
   244 * Pure: fixed idt/idts vs. pttrn/pttrns syntactic categories;
   245 
   246 
   247 *** HOL ***
   248 
   249 * HOL: there is a new splitter `split_asm_tac' that can be used e.g. 
   250   with `addloop' of the simplifier to faciliate case splitting in premises.
   251 
   252 * HOL/TLA: Stephan Merz's formalization of Lamport's Temporal Logic of Actions;
   253 
   254 * HOL/Auth: new protocol proofs including some for the Internet
   255   protocol TLS;
   256 
   257 * HOL/Map: new theory of `maps' a la VDM;
   258 
   259 * HOL/simplifier: simplification procedures nat_cancel_sums for
   260 cancelling out common nat summands from =, <, <= (in)equalities, or
   261 differences; simplification procedures nat_cancel_factor for
   262 cancelling common factor from =, <, <= (in)equalities over natural
   263 sums; nat_cancel contains both kinds of procedures, it is installed by
   264 default in Arith.thy -- this COULD MAKE EXISTING PROOFS FAIL;
   265 
   266 * HOL/simplifier: terms of the form
   267   `? x. P1(x) & ... & Pn(x) & x=t & Q1(x) & ... Qn(x)'  (or t=x)
   268   are rewritten to
   269   `P1(t) & ... & Pn(t) & Q1(t) & ... Qn(t)',
   270   and those of the form
   271   `! x. P1(x) & ... & Pn(x) & x=t & Q1(x) & ... Qn(x) --> R(x)'  (or t=x)
   272   are rewritten to
   273   `P1(t) & ... & Pn(t) & Q1(t) & ... Qn(t) --> R(t)',
   274 
   275 * HOL/datatype
   276   Each datatype `t' now comes with a theorem `split_t_case' of the form
   277 
   278   P(t_case f1 ... fn x) =
   279      ( (!y1 ... ym1. x = C1 y1 ... ym1 --> P(f1 y1 ... ym1)) &
   280         ...
   281        (!y1 ... ymn. x = Cn y1 ... ymn --> P(f1 y1 ... ymn))
   282      )
   283 
   284   and a theorem `split_t_case_asm' of the form
   285 
   286   P(t_case f1 ... fn x) =
   287     ~( (? y1 ... ym1. x = C1 y1 ... ym1 & ~P(f1 y1 ... ym1)) |
   288         ...
   289        (? y1 ... ymn. x = Cn y1 ... ymn & ~P(f1 y1 ... ymn))
   290      )
   291   which can be added to a simpset via `addsplits'. The existing theorems
   292   expand_list_case and expand_option_case have been renamed to
   293   split_list_case and split_option_case.
   294 
   295 * HOL/Arithmetic:
   296   - `pred n' is automatically converted to `n-1'.
   297     Users are strongly encouraged not to use `pred' any longer,
   298     because it will disappear altogether at some point.
   299   - Users are strongly encouraged to write "0 < n" rather than
   300     "n ~= 0". Theorems and proof tools have been modified towards this
   301     `standard'.
   302 
   303 * HOL/Lists:
   304   the function "set_of_list" has been renamed "set" (and its theorems too);
   305   the function "nth" now takes its arguments in the reverse order and
   306   has acquired the infix notation "!" as in "xs!n".
   307 
   308 * HOL/Set: UNIV is now a constant and is no longer translated to Compl{};
   309 
   310 * HOL/Set: The operator (UN x.B x) now abbreviates (UN x:UNIV. B x) and its
   311   specialist theorems (like UN1_I) are gone.  Similarly for (INT x.B x);
   312 
   313 * HOL/record: extensible records with schematic structural subtyping
   314 (single inheritance); EXPERIMENTAL version demonstrating the encoding,
   315 still lacks various theorems and concrete record syntax;
   316 
   317 
   318 *** HOLCF ***
   319 
   320 * removed "axioms" and "generated by" sections;
   321 
   322 * replaced "ops" section by extended "consts" section, which is capable of
   323   handling the continuous function space "->" directly;
   324 
   325 * domain package:
   326   . proves theorems immediately and stores them in the theory,
   327   . creates hierachical name space,
   328   . now uses normal mixfix annotations (instead of cinfix...),
   329   . minor changes to some names and values (for consistency),
   330   . e.g. cases -> casedist, dists_eq -> dist_eqs, [take_lemma] -> take_lemmas,
   331   . separator between mutual domain defs: changed "," to "and",
   332   . improved handling of sort constraints;  now they have to
   333     appear on the left-hand side of the equations only;
   334 
   335 * fixed LAM <x,y,zs>.b syntax;
   336 
   337 * added extended adm_tac to simplifier in HOLCF -- can now discharge
   338 adm (%x. P (t x)), where P is chainfinite and t continuous;
   339 
   340 
   341 *** FOL and ZF ***
   342 
   343 * FOL: there is a new splitter `split_asm_tac' that can be used e.g. 
   344   with `addloop' of the simplifier to faciliate case splitting in premises.
   345 
   346 * qed_spec_mp, qed_goal_spec_mp, qed_goalw_spec_mp are available, as
   347 in HOL, they strip ALL and --> from proved theorems;
   348 
   349 
   350 
   351 New in Isabelle94-8 (May 1997)
   352 ------------------------------
   353 
   354 *** General Changes ***
   355 
   356 * new utilities to build / run / maintain Isabelle etc. (in parts
   357 still somewhat experimental); old Makefiles etc. still functional;
   358 
   359 * new 'Isabelle System Manual';
   360 
   361 * INSTALL text, together with ./configure and ./build scripts;
   362 
   363 * reimplemented type inference for greater efficiency, better error
   364 messages and clean internal interface;
   365 
   366 * prlim command for dealing with lots of subgoals (an easier way of
   367 setting goals_limit);
   368 
   369 
   370 *** Syntax ***
   371 
   372 * supports alternative (named) syntax tables (parser and pretty
   373 printer); internal interface is provided by add_modesyntax(_i);
   374 
   375 * Pure, FOL, ZF, HOL, HOLCF now support symbolic input and output; to
   376 be used in conjunction with the Isabelle symbol font; uses the
   377 "symbols" syntax table;
   378 
   379 * added token_translation interface (may translate name tokens in
   380 arbitrary ways, dependent on their type (free, bound, tfree, ...) and
   381 the current print_mode); IMPORTANT: user print translation functions
   382 are responsible for marking newly introduced bounds
   383 (Syntax.mark_boundT);
   384 
   385 * token translations for modes "xterm" and "xterm_color" that display
   386 names in bold, underline etc. or colors (which requires a color
   387 version of xterm);
   388 
   389 * infixes may now be declared with names independent of their syntax;
   390 
   391 * added typed_print_translation (like print_translation, but may
   392 access type of constant);
   393 
   394 
   395 *** Classical Reasoner ***
   396 
   397 Blast_tac: a new tactic!  It is often more powerful than fast_tac, but has
   398 some limitations.  Blast_tac...
   399   + ignores addss, addbefore, addafter; this restriction is intrinsic
   400   + ignores elimination rules that don't have the correct format
   401 	(the conclusion MUST be a formula variable)
   402   + ignores types, which can make HOL proofs fail
   403   + rules must not require higher-order unification, e.g. apply_type in ZF
   404     [message "Function Var's argument not a bound variable" relates to this]
   405   + its proof strategy is more general but can actually be slower
   406 
   407 * substitution with equality assumptions no longer permutes other
   408 assumptions;
   409 
   410 * minor changes in semantics of addafter (now called addaltern); renamed
   411 setwrapper to setWrapper and compwrapper to compWrapper; added safe wrapper
   412 (and access functions for it);
   413 
   414 * improved combination of classical reasoner and simplifier: 
   415   + functions for handling clasimpsets
   416   + improvement of addss: now the simplifier is called _after_ the
   417     safe steps.
   418   + safe variant of addss called addSss: uses safe simplifications
   419     _during_ the safe steps. It is more complete as it allows multiple 
   420     instantiations of unknowns (e.g. with slow_tac).
   421 
   422 *** Simplifier ***
   423 
   424 * added interface for simplification procedures (functions that
   425 produce *proven* rewrite rules on the fly, depending on current
   426 redex);
   427 
   428 * ordering on terms as parameter (used for ordered rewriting);
   429 
   430 * new functions delcongs, deleqcongs, and Delcongs. richer rep_ss;
   431 
   432 * the solver is now split into a safe and an unsafe part.
   433 This should be invisible for the normal user, except that the
   434 functions setsolver and addsolver have been renamed to setSolver and
   435 addSolver; added safe_asm_full_simp_tac;
   436 
   437 
   438 *** HOL ***
   439 
   440 * a generic induction tactic `induct_tac' which works for all datatypes and
   441 also for type `nat';
   442 
   443 * a generic case distinction tactic `exhaust_tac' which works for all
   444 datatypes and also for type `nat';
   445 
   446 * each datatype comes with a function `size';
   447 
   448 * patterns in case expressions allow tuple patterns as arguments to
   449 constructors, for example `case x of [] => ... | (x,y,z)#ps => ...';
   450 
   451 * primrec now also works with type nat;
   452 
   453 * recdef: a new declaration form, allows general recursive functions to be
   454 defined in theory files.  See HOL/ex/Fib, HOL/ex/Primes, HOL/Subst/Unify.
   455 
   456 * the constant for negation has been renamed from "not" to "Not" to
   457 harmonize with FOL, ZF, LK, etc.;
   458 
   459 * HOL/ex/LFilter theory of a corecursive "filter" functional for
   460 infinite lists;
   461 
   462 * HOL/Modelcheck demonstrates invocation of model checker oracle;
   463 
   464 * HOL/ex/Ring.thy declares cring_simp, which solves equational
   465 problems in commutative rings, using axiomatic type classes for + and *;
   466 
   467 * more examples in HOL/MiniML and HOL/Auth;
   468 
   469 * more default rewrite rules for quantifiers, union/intersection;
   470 
   471 * a new constant `arbitrary == @x.False';
   472 
   473 * HOLCF/IOA replaces old HOL/IOA;
   474 
   475 * HOLCF changes: derived all rules and arities 
   476   + axiomatic type classes instead of classes 
   477   + typedef instead of faking type definitions
   478   + eliminated the internal constants less_fun, less_cfun, UU_fun, UU_cfun etc.
   479   + new axclasses cpo, chfin, flat with flat < chfin < pcpo < cpo < po
   480   + eliminated the types void, one, tr
   481   + use unit lift and bool lift (with translations) instead of one and tr
   482   + eliminated blift from Lift3.thy (use Def instead of blift)
   483   all eliminated rules are derived as theorems --> no visible changes ;
   484 
   485 
   486 *** ZF ***
   487 
   488 * ZF now has Fast_tac, Simp_tac and Auto_tac.  Union_iff is a now a default
   489 rewrite rule; this may affect some proofs.  eq_cs is gone but can be put back
   490 as ZF_cs addSIs [equalityI];
   491 
   492 
   493 
   494 New in Isabelle94-7 (November 96)
   495 ---------------------------------
   496 
   497 * allowing negative levels (as offsets) in prlev and choplev;
   498 
   499 * super-linear speedup for large simplifications;
   500 
   501 * FOL, ZF and HOL now use miniscoping: rewriting pushes
   502 quantifications in as far as possible (COULD MAKE EXISTING PROOFS
   503 FAIL); can suppress it using the command Delsimps (ex_simps @
   504 all_simps); De Morgan laws are also now included, by default;
   505 
   506 * improved printing of ==>  :  ~:
   507 
   508 * new object-logic "Sequents" adds linear logic, while replacing LK
   509 and Modal (thanks to Sara Kalvala);
   510 
   511 * HOL/Auth: correctness proofs for authentication protocols;
   512 
   513 * HOL: new auto_tac combines rewriting and classical reasoning (many
   514 examples on HOL/Auth);
   515 
   516 * HOL: new command AddIffs for declaring theorems of the form P=Q to
   517 the rewriter and classical reasoner simultaneously;
   518 
   519 * function uresult no longer returns theorems in "standard" format;
   520 regain previous version by: val uresult = standard o uresult;
   521 
   522 
   523 
   524 New in Isabelle94-6
   525 -------------------
   526 
   527 * oracles -- these establish an interface between Isabelle and trusted
   528 external reasoners, which may deliver results as theorems;
   529 
   530 * proof objects (in particular record all uses of oracles);
   531 
   532 * Simp_tac, Fast_tac, etc. that refer to implicit simpset / claset;
   533 
   534 * "constdefs" section in theory files;
   535 
   536 * "primrec" section (HOL) no longer requires names;
   537 
   538 * internal type "tactic" now simply "thm -> thm Sequence.seq";
   539 
   540 
   541 
   542 New in Isabelle94-5
   543 -------------------
   544 
   545 * reduced space requirements;
   546 
   547 * automatic HTML generation from theories;
   548 
   549 * theory files no longer require "..." (quotes) around most types;
   550 
   551 * new examples, including two proofs of the Church-Rosser theorem;
   552 
   553 * non-curried (1994) version of HOL is no longer distributed;
   554 
   555 
   556 
   557 New in Isabelle94-4
   558 -------------------
   559 
   560 * greatly reduced space requirements;
   561 
   562 * theory files (.thy) no longer require \...\ escapes at line breaks;
   563 
   564 * searchable theorem database (see the section "Retrieving theorems" on 
   565 page 8 of the Reference Manual);
   566 
   567 * new examples, including Grabczewski's monumental case study of the
   568 Axiom of Choice;
   569 
   570 * The previous version of HOL renamed to Old_HOL;
   571 
   572 * The new version of HOL (previously called CHOL) uses a curried syntax 
   573 for functions.  Application looks like f a b instead of f(a,b);
   574 
   575 * Mutually recursive inductive definitions finally work in HOL;
   576 
   577 * In ZF, pattern-matching on tuples is now available in all abstractions and
   578 translates to the operator "split";
   579 
   580 
   581 
   582 New in Isabelle94-3
   583 -------------------
   584 
   585 * new infix operator, addss, allowing the classical reasoner to 
   586 perform simplification at each step of its search.  Example:
   587 	fast_tac (cs addss ss)
   588 
   589 * a new logic, CHOL, the same as HOL, but with a curried syntax 
   590 for functions.  Application looks like f a b instead of f(a,b).  Also pairs 
   591 look like (a,b) instead of <a,b>;
   592 
   593 * PLEASE NOTE: CHOL will eventually replace HOL!
   594 
   595 * In CHOL, pattern-matching on tuples is now available in all abstractions.
   596 It translates to the operator "split".  A new theory of integers is available;
   597 
   598 * In ZF, integer numerals now denote two's-complement binary integers.
   599 Arithmetic operations can be performed by rewriting.  See ZF/ex/Bin.ML;
   600 
   601 * Many new examples: I/O automata, Church-Rosser theorem, equivalents 
   602 of the Axiom of Choice;
   603 
   604 
   605 
   606 New in Isabelle94-2
   607 -------------------
   608 
   609 * Significantly faster resolution;  
   610 
   611 * the different sections in a .thy file can now be mixed and repeated
   612 freely;
   613 
   614 * Database of theorems for FOL, HOL and ZF.  New
   615 commands including qed, qed_goal and bind_thm store theorems in the database.
   616 
   617 * Simple database queries: return a named theorem (get_thm) or all theorems of
   618 a given theory (thms_of), or find out what theory a theorem was proved in
   619 (theory_of_thm);
   620 
   621 * Bugs fixed in the inductive definition and datatype packages;
   622 
   623 * The classical reasoner provides deepen_tac and depth_tac, making FOL_dup_cs
   624 and HOL_dup_cs obsolete;
   625 
   626 * Syntactic ambiguities caused by the new treatment of syntax in Isabelle94-1
   627 have been removed;
   628 
   629 * Simpler definition of function space in ZF;
   630 
   631 * new results about cardinal and ordinal arithmetic in ZF;
   632 
   633 * 'subtype' facility in HOL for introducing new types as subsets of existing
   634 types;
   635 
   636 
   637 $Id$