CHANGES-92f.txt
author wenzelm
Thu Aug 27 20:46:36 1998 +0200 (1998-08-27)
changeset 5400 645f46a24c72
parent 0 a5a9c433f639
permissions -rw-r--r--
made tutorial first;
     1 **** Isabelle-92f : a faster version of Isabelle-92 ****
     2 
     3 Isabelle now runs faster through a combination of improvements: pattern
     4 unification, discrimination nets and removal of assumptions during
     5 simplification.  Classical reasoning (e.g. fast_tac) runs up to 30% faster
     6 when large numbers of rules are involved.  Rewriting (e.g. SIMP_TAC) runs
     7 up to 3 times faster for large subgoals.  
     8 
     9 The new version will not benefit everybody; unless you require greater
    10 speed, it may be best to stay with the existing version.  The new changes
    11 have not been documented properly, and there are a few incompatibilities.
    12 
    13 THE SPEEDUPS
    14 
    15 Pattern unification is completely invisible to users.  It efficiently
    16 handles a common case of higher-order unification.
    17 
    18 Discrimination nets replace the old stringtrees.  They provide fast lookup
    19 in a large set of rules for matching or unification.  New "net" tactics
    20 replace the "compat_..." tactics based on stringtrees.  Tactics
    21 biresolve_from_nets_tac, bimatch_from_nets_tac, resolve_from_net_tac and
    22 match_from_net_tac take a net, rather than a list of rules, and perform
    23 resolution or matching.  Tactics net_biresolve_tac, net_bimatch_tac
    24 net_resolve_tac and net_match_tac take a list of rules, build a net
    25 (internally) and perform resolution or matching.
    26 
    27 The tactical METAHYPS, which allows a subgoal's hypotheses to be taken as a
    28 list of theorems, has been extended to handle unknowns (although not type
    29 unknowns).  The simplification tactics now use METAHYPS to economise on
    30 storage consumption, and to avoid problems involving "parameters" bound in
    31 a subgoal.  The modified simplifier now requires the auto_tac to take an
    32 extra argument: a list of theorems, which represents the assumptions of the
    33 current subgoal.
    34 
    35 OTHER CHANGES
    36 
    37 Apart from minor improvements in Pure Isabelle, the main other changes are
    38 extensions to object-logics.  HOL now contains a treatment of co-induction
    39 and co-recursion, while ZF contains a formalization of equivalence classes,
    40 the integers and binary arithmetic.  None of this material is documented.