Source file `standard.ml`

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(**************************************************************************)
(*                                                                        *)
(*                                 OCaml                                  *)
(*                                                                        *)
(*                 Simon Cruanes                                          *)
(*                                                                        *)
(*   Copyright 2017 Institut National de Recherche en Informatique et     *)
(*     en Automatique.                                                    *)
(*                                                                        *)
(*   All rights reserved.  This file is distributed under the terms of    *)
(*   the GNU Lesser General Public License version 2.1, with the          *)
(*   special exception on linking described in the file LICENSE.          *)
(*                                                                        *)
(**************************************************************************)

(** Monadic traversors over {!Stdlib.Seq}.

    This [Make] functor produces functions to traverse {!Stdlib.Seq}
    sequences, when the function provided by the user is within a monad.

    The [Make] functor does not export a new type: it only exports
    traversors for the existing type exported by the Stdlib. If you need tighter
    integration between your monad and the sequence, checkout
    {!Seqes.Monadic}.

    The buld of the documentation is located in the {!Seqes.Sigs1} module.
    Familiarity with the {!Stdlib.Seq} module is also assumed.
 *)
module Make1(Mon: Sigs1.MONAD1)
: Sigs1.SEQMON1TRAVERSORS
    with type 'a mon := 'a Mon.t
    with type 'a callermon := 'a Mon.t
    with type 'a t := 'a Stdlib.Seq.t
= struct

  let return = Mon.return
  let ( let* ) = Mon.bind

  let rec fold_left f acc seq =
    let n = seq () in
    match n with
    | Stdlib.Seq.Nil -> return acc
    | Cons (x, next) ->
        let* acc = f acc x in
        fold_left f acc next

  let rec iter f seq =
    let n = seq () in
    match n with
    | Stdlib.Seq.Nil -> return ()
    | Cons (x, next) ->
        let* () = f x in
        iter f next

  let rec iteri_aux f i xs =
    let n = xs () in
    match n with
    | Stdlib.Seq.Nil ->
        return ()
    | Cons (x, xs) ->
        let* () = f i x in
        iteri_aux f (i+1) xs
  let[@inline] iteri f xs = iteri_aux f 0 xs

  let rec fold_lefti_aux f accu i xs =
    let n = xs () in
    match n with
    | Stdlib.Seq.Nil ->
        return accu
    | Cons (x, xs) ->
        let* accu = f accu i x in
        fold_lefti_aux f accu (i+1) xs
  let[@inline] fold_lefti f accu xs = fold_lefti_aux f accu 0 xs

  let rec for_all p xs =
    let n = xs () in
    match n with
    | Stdlib.Seq.Nil ->
        return true
    | Cons (x, xs) ->
        let* b = p x in
        if b then
          for_all p xs
        else
          return false

  let rec exists p xs =
    let n = xs () in
    match n with
    | Stdlib.Seq.Nil ->
        return false
    | Cons (x, xs) ->
        let* b = p x in
        if b then
          return true
        else
          exists p xs

  let rec find p xs =
    let n = xs () in
    match n with
    | Stdlib.Seq.Nil ->
        return None
    | Cons (x, xs) ->
        let* b = p x in
        if b then return (Some x) else find p xs

  let rec find_map f xs =
    let n = xs () in
    match n with
    | Stdlib.Seq.Nil ->
        return None
    | Cons (x, xs) ->
        let* o = f x in
        match o with
        | None ->
            find_map f xs
        | Some _ as result ->
            return result

  let rec iter2 f xs ys =
    let n = xs () in
    match n with
    | Stdlib.Seq.Nil ->
        return ()
    | Cons (x, xs) ->
        let n = ys () in
        match n with
        | Stdlib.Seq.Nil ->
            return ()
        | Cons (y, ys) ->
            let* () = f x y in
            iter2 f xs ys

  let rec fold_left2 f accu xs ys =
    let n = xs () in
    match n with
    | Stdlib.Seq.Nil ->
        return accu
    | Cons (x, xs) ->
        let n = ys () in
        match n with
        | Stdlib.Seq.Nil ->
            return accu
        | Cons (y, ys) ->
            let* accu = f accu x y in
            fold_left2 f accu xs ys

  let rec for_all2 f xs ys =
    let n = xs () in
    match n with
    | Stdlib.Seq.Nil ->
        return true
    | Cons (x, xs) ->
        let n = ys () in
        match n with
        | Stdlib.Seq.Nil ->
            return true
        | Cons (y, ys) ->
            let* b = f x y in
            if b then
              for_all2 f xs ys
            else
              return false

  let rec exists2 f xs ys =
    let n = xs () in
    match n with
    | Stdlib.Seq.Nil ->
        return false
    | Cons (x, xs) ->
        let n = ys () in
        match n with
        | Stdlib.Seq.Nil ->
            return false
        | Cons (y, ys) ->
            let* b = f x y in
            if b then
              return true
            else
              exists2 f xs ys

end


module Make2(Mon: Sigs2.MONAD2)
: Sigs2.SEQMON2TRAVERSORS
    with type ('a, 'e) mon := ('a, 'e) Mon.t
    with type ('a, 'e) callermon := ('a, 'e) Mon.t
    with type ('a, 'e) t := 'a Stdlib.Seq.t
= struct

  let return = Mon.return
  let ( let* ) = Mon.bind

  let rec fold_left f acc seq =
    let n = seq () in
    match n with
    | Stdlib.Seq.Nil -> return acc
    | Cons (x, next) ->
        let* acc = f acc x in
        fold_left f acc next

  let rec iter f seq =
    let n = seq () in
    match n with
    | Stdlib.Seq.Nil -> return ()
    | Cons (x, next) ->
        let* () = f x in
        iter f next

  let rec iteri_aux f i xs =
    let n = xs () in
    match n with
    | Stdlib.Seq.Nil ->
        return ()
    | Cons (x, xs) ->
        let* () = f i x in
        iteri_aux f (i+1) xs
  let[@inline] iteri f xs = iteri_aux f 0 xs

  let rec fold_lefti_aux f accu i xs =
    let n = xs () in
    match n with
    | Stdlib.Seq.Nil ->
        return accu
    | Cons (x, xs) ->
        let* accu = f accu i x in
        fold_lefti_aux f accu (i+1) xs
  let[@inline] fold_lefti f accu xs = fold_lefti_aux f accu 0 xs

  let rec for_all p xs =
    let n = xs () in
    match n with
    | Stdlib.Seq.Nil ->
        return true
    | Cons (x, xs) ->
        let* b = p x in
        if b then
          for_all p xs
        else
          return false

  let rec exists p xs =
    let n = xs () in
    match n with
    | Stdlib.Seq.Nil ->
        return false
    | Cons (x, xs) ->
        let* b = p x in
        if b then
          return true
        else
          exists p xs

  let rec find p xs =
    let n = xs () in
    match n with
    | Stdlib.Seq.Nil ->
        return None
    | Cons (x, xs) ->
        let* b = p x in
        if b then return (Some x) else find p xs

  let rec find_map f xs =
    let n = xs () in
    match n with
    | Stdlib.Seq.Nil ->
        return None
    | Cons (x, xs) ->
        let* o = f x in
        match o with
        | None ->
            find_map f xs
        | Some _ as result ->
            return result

  let rec iter2 f xs ys =
    let n = xs () in
    match n with
    | Stdlib.Seq.Nil ->
        return ()
    | Cons (x, xs) ->
        let n = ys () in
        match n with
        | Stdlib.Seq.Nil ->
            return ()
        | Cons (y, ys) ->
            let* () = f x y in
            iter2 f xs ys

  let rec fold_left2 f accu xs ys =
    let n = xs () in
    match n with
    | Stdlib.Seq.Nil ->
        return accu
    | Cons (x, xs) ->
        let n = ys () in
        match n with
        | Stdlib.Seq.Nil ->
            return accu
        | Cons (y, ys) ->
            let* accu = f accu x y in
            fold_left2 f accu xs ys

  let rec for_all2 f xs ys =
    let n = xs () in
    match n with
    | Stdlib.Seq.Nil ->
        return true
    | Cons (x, xs) ->
        let n = ys () in
        match n with
        | Stdlib.Seq.Nil ->
            return true
        | Cons (y, ys) ->
            let* b = f x y in
            if b then
              for_all2 f xs ys
            else
              return false

  let rec exists2 f xs ys =
    let n = xs () in
    match n with
    | Stdlib.Seq.Nil ->
        return false
    | Cons (x, xs) ->
        let n = ys () in
        match n with
        | Stdlib.Seq.Nil ->
            return false
        | Cons (y, ys) ->
            let* b = f x y in
            if b then
              return true
            else
              exists2 f xs ys

end