Generating Atoms

library(strings) defines three predicates for generating atoms.

gensym(+Prefix, -Atom)

is equivalent to concat_atom([Prefix, N], Atom), where N is the next number in the sequence associated with Prefix. Notionally, each Prefix has its own counter, starting with zero. Prefix must be an atom. Examples:

          | ?- gensym(a, X).
          
          X = a1
          
          | ?- gensym(a, X).
          
          X = a2
          
          | ?- gensym(b, X).
          
          X = b1
          
          | ?- gensym(1, X).
          
          no
          

gensym(-Atom)

uses the Prefix %. Example:

          | ?- gensym(X).
          
          X = '%58'
          

cgensym(+Prefix, ?Atom)

if Atom is a variable, it generates a new atom using gensym/2. Otherwise, Prefix and Atom should be atoms. The name is to be read as "conditionally generate symbol".

These predicates are included for compatibility with the DEC-10 Prolog library, which has contained them for several years. cgensym/2 will do nothing to Atom if it is already bound; otherwise it is just like gensym/2.