Gensym (Generate Symbols) is an old library for generating
unique symbols (atoms). Such symbols are generated from a base atom
which gets a sequence number appended. Of course there is no guarantee
that
catch22 is not an already defined atom and therefore one
must be aware these atoms are only unique in an isolated context.
The SWI-Prolog gensym library is thread-safe. The sequence numbers
are global over all threads and therefore generated atoms are unique
over all threads.
- gensym(+Base,
-Unique)
- Generate <Base>1, <Base>2,
etc atoms on each subsequent call. Note that there is nothing that
prevents other parts of the application to‘invent' the same
identifier. The predicate
gensym/2 is thread-safe
in the sense that two threads generating identifiers from the same Base
will never generate the same identifier.
- See also
- uuid/1, term_hash/2, variant_sha1/2
may be used to generate various unique or content-based identifiers
safely.
- reset_gensym
- Reset gensym for all registered keys. This predicate is available for
compatibility only. New code is strongly advised to avoid the use of
reset_gensym or at least to reset only the keys used by your program to
avoid unexpected side effects on other components.
- reset_gensym(+Base)
- Restart generation of identifiers from Base at <Base>1.
Used to make sure a program produces the same results on subsequent
runs. Use with care.