/usr/local/lib/swipl/library/terms.pl
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 same_functor(?Term1, ?Term2) is semidet
 same_functor(?Term1, ?Term2, -Arity) is semidet
 same_functor(?Term1, ?Term2, ?Name, ?Arity) is semidet
True when Term1 and Term2 are terms that have the same functor (Name/Arity). The arguments must be sufficiently instantiated, which means either Term1 or Term2 must be bound or both Name and Arity must be bound.

If Arity is 0, Term1 and Term2 are unified with Name for compatibility.

Compatibility
- SICStus