SWI-Prolog -- name/2

Availability:built-in

name(?Atomic, ?CodeList)

CodeList is a list of character codes representing the same text as Atomic. Each of the arguments may be a variable, but not both. When CodeList describes an integer or floating point number and Atomic is a variable, Atomic will be unified with the numeric value described by CodeList (e.g.,

name(N, 
"300"), 400 is N + 100

succeeds). If CodeList is not a representation of a number, Atomic will be unified with the atom with the name given by the character code list. When Atomic is an atom or number, the unquoted print representation of it as a character code list will be unified with CodeList.

Note that it is not possible to produce the atom '300' using name/2, and that name(300, CodeList), name('300', CodeList) succeeds. For these reasons, new code should consider using the ISO predicates atom_codes/2 or number_codes/2.^{103Unfortunately,
the ISO predicates provide no neat way to check that a string can be
interpreted as a number. The most sensible way is to use catch/3
to catch the exception from number_codes/2;
however, this is both slow and cumbersome. We consider making, e.g., number_codes(N,
"abc") fail silently in future versions.} See also atom_number/2.