val pair : ?eq:(('a * 'b) -> ('a * 'b) -> bool) -> 'a signal -> 'b signal -> ('a * 'b) signal
val fst : ?eq:('a -> 'a -> bool) -> ('a * 'b) signal -> 'a signal
val snd : ?eq:('a -> 'a -> bool) -> ('b * 'a) signal -> 'a signal