numbervars/3
meta-logicalnumbervars(
+-Term,
+FirstVar,
-LastVar)
instantiates each of the variables in Term to a term of the form
'$VAR'(
N)
.
FirstVar is used as the value of N for the first variable in Term (starting from the left). The second distinct variable in Term is given a value of N satisfying "N is FirstVar+1"; the third distinct variable gets the value FirstVar+2, and so on. The last variable in Term has the value LastVar-1.
Notice that in the example below, display/1
is used
rather than write/1
. This is because write/1
treats terms of the form '$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,
the variable bindings will also be printed out as follows:
Term = foo(W,W,X), A = W, B = X
instantiation_error
type_error
| ?- Term = foo(A, A, B), numbervars(Term, 22, _), display(Term). foo($VAR(22),$VAR(22),$VAR(23))
write_term/1
, write_canonical/1