==/2, \==/2

Synopsis

+Term1 == +Term2

Succeeds if the terms currently instantiating Term1 and Term2 are literally identical (in particular, variables in equivalent positions in the two terms must be identical).

+Term1 \== +Term2

Succeeds if the terms currently instantiating Term1 and Term2 are not literally identical.

Arguments

Term1 term

Term2 term

Description

Query (A) fails because Term1 and Term2 are distinct uninstantiated variables. However, query (B) succeeds because the first goal unifies the two variables:

     | ?- Term1 == Term2.   (A)
     
     no
     

     | ?- Term1 = Term2, Term1 == Term2.   (B)
     
     yes
     

Query (C) succeeds because Term1 and Term2 are distinct uninstantiated variables. However, query (D) fails because the first goal unifies the two variables.

     | ?- Term1 \== Term2.  (C)
     
     yes
     

     | ?- Term1 = Term2, Term1 \== Term2.  (D)
     
     no
     

See also

compare/3, @</2, @=</2, @>/2, @>=/2 ref-lte