{ $description "Tests if the sequence contains an element satisfying the predicate, by applying the predicate to each element in turn until a true value is found. If the sequence is empty or if the end of the sequence is reached, outputs " { $link f } "." } ;
+{ $description "Tests if the sequence does not contain any element satisfying the predicate, by applying the predicate to each element in turn until a true value is found. If the sequence is empty or if the end of the sequence is reached, outputs " { $link t } "." } ;
{ $description "Tests if all elements in the sequence satisfy the predicate by checking each element in turn. Given an empty sequence, vacuously outputs " { $link t } "." } ;