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numbervars/3
numbervars(+Term, +FirstVar, -LastVar)
instantiates each of the variables in Term to a term of the form
'$VAR'(N)
.
term
integer, must be nonvar
integer
FirstVar is used as the value of N for the first variable in Term (starting from the left). The second distinct variable in Term is given a value of N satisfying “N is FirstVar+1”; the third distinct variable gets the value FirstVar+2, and so on. The last variable in Term has the value LastVar-1.
Notice that in the example below, write_canonical/1
is used rather than
writeq/1
. This is because writeq/1
treats terms of the
form '$VAR'(N)
specially; it writes ‘A’ if
N=0, ‘B’ if N=1, …‘Z’ if N=25,
‘A1’ if N=26, etc. That is why, if you type the goal in
the example below, then the variable bindings will also be printed out as
follows:
Term = foo(W,W,X), A = W, B = X
instantiation_error
FirstVar is uninstantiated
type_error
FirstVar is not an integer
| ?- Term = foo(A, A, B), numbervars(Term, 22, _), write_canonical(Term). foo('$VAR'(22),'$VAR'(22),'$VAR'(23))
ref-lte-anv,
write_term/[2,3]
.