mem' : ('a -> 'b -> bool) -> 'a -> 'b list -> bool
SYNOPSIS
Tests if an element is equivalent to a member of a list w.r.t. some relation.
DESCRIPTION
If r is a binary relation, x an element and l a list, the call
mem' r x l tests if there is an element in the list l that is equivalent to
x according to r, that is, if r x x' holds for some x' in l. The
function mem is the special case where the relation is equality.
FAILURE CONDITIONS
Fails only if the relation r fails.
EXAMPLE
# mem' (fun x y -> abs(x) = abs(y)) (-1) [1;2;3];;
val it : bool = true
# mem' (fun x y -> abs(x) = abs(y)) (-1) [2;3;4];;
val it : bool = false
USES
Set operations modulo some equivalence such as alpha-equivalence.