Module Let_syntax.Let_syntax
val return : 'a -> ('a, 'i, 'i) X.tval bind : ('a, 'i, 'j) X.t -> f:('a -> ('b, 'j, 'k) X.t) -> ('b, 'i, 'k) X.tval map : ('a, 'i, 'j) X.t -> f:('a -> 'b) -> ('b, 'i, 'j) X.tval both : ('a, 'i, 'j) X.t -> ('b, 'j, 'k) X.t -> ('a * 'b, 'i, 'k) X.t