11.3.234 term_variables/2   [ISO]

Synopsis

term_variables(+Term, -Variables)   since release 4.3 True if Variables is the list of variables occurring in Term, without duplicates, in first occurrence order.

Arguments

Term

Any term, a cyclic term is also accepted.

-Variables

The variables in the term. Must be a variable or a list.

Exceptions

type_error

Variables is not a variable or a list.

Examples

     | ?- term_variables(f(A, B, A), Vs).
     Vs = [A,B] ?
     yes
     | ?- term_variables(f(a, b, a), Vs).
     Vs = [] ?
     yes
     | ?- T=[A,B|T], term_variables(f(C,T), Vs).
     T = [A,B,A,B,A,B,A,B,A,B|...],
     Vs = [C,A,B] ?
     yes

See Also

ref-lte-act.