14.8.3 Other Changes

• The windowed executable (spwin.exe) on Windows now saves and reads the command history (see Command Line Editing).
• write/[1,2] is now much faster when writing atomic terms.
• assertz/1 and friends are now faster when asserting facts, i.e. clauses without bodies.
• library(terms): the new predicate term_hash/3 allows more control over the hashing behavior and hash algorithm used.

  Notable new features: a new, better, default hash algorithm and several other algorithms, including the 4.0.4 version, are available; it is possible to obtain a full 32-bit hash value; it is possible to get an instantiation error or hash value when the term being hashed is nonground.

  term_hash/[2,4] has been changed to use a better hash function by default. The new hash function gives fewer collisions in general, and gives the same value on all platforms.

  Please note: The change of hash function is an incompatible change that may affect programs or data that depend on the old hash algorithm. The old behavior can be obtained as follows:

  %% Pre 4.0.5 version
  term_hash_4_0_4(Term, Hash) :-
     term_hash(Term, [algorithm('sicstus-4.0.4')], Hash).
  
  term_hash_4_0_4(Term, Depth, Range, Value) :-
     term_hash(Term, [algorithm('sicstus-4.0.4'), depth(Depth), range(Range)], Hash).
  

• library(debugger_examples) updated.
• Extended Runtime systems (a separate product, adding the compiler to runtime systems) now require a license at runtime. By default spld will embed the license into the executable.
• The hook user:error_exception/1 is now called with the exception term specified by ISO Prolog, i.e. the same term that is seen by catch/3 and on_exception/3. It used to be called with an internal representation of the exception. This affects error exceptions, i.e. those with functor error/2. The old (pre 4.0.5) value passed to user:error_exception/1 is the second argument of the error/2 structure.

  Please note: This is an incompatible change. Old code that uses user:error_exception/1 may need to be updated. If the old code looked like:

  %% Pre 4.0.5 version
  user:error_exception(Old) :- do_something(Old).
  

  then it can be rewritten as follows (which will also work in older versions of SICStus Prolog):

  %% >= 4.0.5 version
  user:error_exception(New) :-
     ( New = error(_, Old) -> true; Old = New),
     do_something(Old).
  

• trimcore/0 is now more thorough when releasing memory back to the operating system. This also affects the trimcore-variant used by the top level.
• It is now possible to tell SICStus to use malloc() et al. as memory manager instead of the default custom allocator.

  malloc() is selected when starting sicstus with the new option -m; when initializing the SICStus runtime with the environment variable SP_USE_MALLOC set to yes; for SICStus runtimes built with the new spld option --memhook=malloc; and when calling SP_set_memalloc_hooks() with the new option SP_SET_MEMALLOC_HOOKS_HINT_USE_MALLOC. See SP_set_memalloc_hooks in the SICStus Prolog Manual.

• library(clpfd): unification with domain variables as well as propositional combinations of arithmetic constraints have been accelerated.