# Module type `Monad.ListS`

List combinators

`val map : ('a -> 'b t) -> 'a list -> 'b list t`

`List.map f l`

maps`f`

on the elements of`l`

in left to right order.

`val map_right : ('a -> 'b t) -> 'a list -> 'b list t`

`List.map f l`

maps`f`

on the elements of`l`

in right to left order.

`val fold_right : ('a -> 'b -> 'b t) -> 'a list -> 'b -> 'b t`

Like the regular

`List.fold_right`

. The monadic effects are threaded right to left.Note: many monads behave poorly with right-to-left order. For instance a failure monad would still have to traverse the whole list in order to fail and failure needs to be propagated through the rest of the list in binds which are now spurious. It is also the worst case for substitution monads (aka free monads), exposing the quadratic behaviour.

`val fold_left : ('a -> 'b -> 'a t) -> 'a -> 'b list -> 'a t`

Like the regular

`List.fold_left`

. The monadic effects are threaded left to right. It is tail-recursive if the`(>>=)`

operator calls its second argument in a tail position.

`val iter : ('a -> unit t) -> 'a list -> unit t`

Like the regular

`List.iter`

. The monadic effects are threaded left to right. It is tail-recurisve if the`>>`

operator calls its second argument in a tail position.

`val map_filter : ('a -> 'b option t) -> 'a list -> 'b list t`

Like the regular

`CList.map_filter`

. The monadic effects are threaded left to right.