Checks whether the provided element is there, using equal.

fold t ~init ~f returns f (... f (f (f init e1) e2) e3 ...) en, where e1..en are the elements of t

fold_result t ~init ~f is a short-circuiting version of fold that runs in the Result monad. If f returns an Error _, that value is returned without any additional invocations of f.

fold_until t ~init ~f ~finish is a short-circuiting version of fold. If f returns Stop _ the computation ceases and results in that value. If f returns Continue _, the fold will proceed. If f never returns Stop _, the final result is computed by finish.

Example:

  type maybe_negative =
    | Found_negative of int
    | All_nonnegative of { sum : int }

  (** [first_neg_or_sum list] returns the first negative number in [list], if any,
      otherwise returns the sum of the list. *)
  let first_neg_or_sum =
    List.fold_until ~init:0
      ~f:(fun sum x ->
        if x < 0
        then Stop (Found_negative x)
        else Continue (sum + x))
      ~finish:(fun sum -> All_nonnegative { sum })
  ;;

  let x = first_neg_or_sum [1; 2; 3; 4; 5]
  val x : maybe_negative = All_nonnegative {sum = 15}

  let y = first_neg_or_sum [1; 2; -3; 4; 5]
  val y : maybe_negative = Found_negative -3

Returns true if and only if there exists an element for which the provided function evaluates to true. This is a short-circuiting operation.

Returns true if and only if the provided function evaluates to true for all elements. This is a short-circuiting operation.

Returns the number of elements for which the provided function evaluates to true.

Returns the sum of f i for all i in the container.

Returns as an option the first element for which f evaluates to true.

Returns the first evaluation of f that returns Some, and returns None if there is no such element.

Returns a minimum (resp maximum) element from the collection using the provided compare function, or None if the collection is empty. In case of a tie, the first element encountered while traversing the collection is returned. The implementation uses fold so it has the same complexity as fold.

t >>= f returns a computation that sequences the computations represented by two monad elements. The resulting computation first does t to yield a value v, and then runs the computation returned by f v.

t >>| f is t >>= (fun a -> return (f a)).

bind t ~f = t >>= f

return v returns the (trivial) computation that returns v.

map t ~f is t >>| f.

join t is t >>= (fun t' -> t').

ignore_m t is map t ~f:(fun _ -> ()). ignore_m used to be called ignore, but we decided that was a bad name, because it shadowed the widely used Caml.ignore. Some monads still do let ignore = ignore_m for historical reasons.

Like all, but ensures that every monadic value in the list produces a unit value, all of which are discarded rather than being collected into a list.

These are convenient to have in scope when programming with a monad: