Module Let_syntax.Let_syntax
val return : 'a -> ('a, _, _) X.tval bind : ('a, 'd, 'e) X.t -> f:('a -> ('b, 'd, 'e) X.t) -> ('b, 'd, 'e) X.tval map : ('a, 'd, 'e) X.t -> f:('a -> 'b) -> ('b, 'd, 'e) X.tval both : ('a, 'd, 'e) X.t -> ('b, 'd, 'e) X.t -> ('a * 'b, 'd, 'e) X.t