HANDBOOK / GENTLE PRIMER / A Summary of Predefined Predicates /

The Predicate where

The predicate where is defined for each type. It simply copies its input parameter to its output parameter. Hence, it may be used to construct a value and assign it to a variable as in

   where(list(red, nil) -> L)
or to inspect a value and define variables with subterms as in

   where(L -> list(Head, Tail))
This predicate is of particular use in alternative statements and is discussed in the corresponding section.