Base interface for equatable polymorphic binary types.
type ('a, 'b) tAbstract type for equatable values.
val equal : 'a equality -> 'b equality -> ('a, 'b) t equalityeq equal_a equal_b t1 t2 tests if the values t1 and t2 are equal using the equal_a and equal_b functions to compare the contained values of type 'a and 'b respectively.