Isabelle NEWS -- history of user-visible changes

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New in Isabelle94-8 (April 1997)

--------------------------------

*** General Changes ***

* new utilities to build / run / maintain Isabelle etc. (in parts

still somewhat experimental); old Makefiles etc. still functional;

* INSTALL text, together with ./configure and ./build scripts;

* reimplemented type inference for greater efficiency;

* prlim command for dealing with lots of subgoals (an easier way of

setting goals_limit);

*** Syntax

* 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);

* token translations for modes "xterm" and "xterm_color" that display

names in bold, underline etc. or colors;

* now supports alternative (named) syntax tables (parser and pretty

printer); internal interface is provided by add_modesyntax(_i);

* 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: new

addss, auto_tac, functions for handling clasimpsets, ...  Now, the

simplification is safe (therefore moved to safe_step_tac) and thus

more complete, as multiple instantiation of unknowns (with slow_tac).

COULD MAKE EXISTING PROOFS FAIL; in case of problems with

old proofs, use unsafe_addss and unsafe_auto_tac

*** Simplifier ***

* 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.

* ordering on terms as parameter (used for ordered rewriting);

added interface for simplification procedures (functions that produce *proven*

rewrite rules on the fly, depending on current redex);

*** HOL ***

* 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;

* 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/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;

* 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;

$Id$