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updated CCBatch (more optimizations and type-safety,
enforcing some structural constraints with GADT)
This commit is contained in:
Simon Cruanes
parent
5567b12b79
commit
40f8955b34
2 changed files with 77 additions and 28 deletions
103
core/CCBatch.ml
103
core/CCBatch.ml
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@ -47,6 +47,8 @@ module type S = sig
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(** {6 Combinators} *)
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val id : ('a, 'a) op
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val map : ('a -> 'b) -> ('a, 'b) op
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val filter : ('a -> bool) -> ('a,'a) op
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@ -62,22 +64,21 @@ end
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module Make(C : COLLECTION) = struct
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type 'a t = 'a C.t
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type (_,_) op =
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| Map : ('a -> 'b) -> ('a, 'b) op
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| Filter : ('a -> bool) -> ('a, 'a) op
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| FilterMap : ('a -> 'b option) -> ('a,'b) op
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| FlatMap : ('a -> 'b t) -> ('a,'b) op
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| Compose : ('a,'b) op * ('b, 'c) op -> ('a, 'c) op
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| Id : ('a,'a) op
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| Compose : ('a,'b) base_op * ('b, 'c) op -> ('a, 'c) op
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and (_,_) base_op =
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| Map : ('a -> 'b) -> ('a, 'b) base_op
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| Filter : ('a -> bool) -> ('a, 'a) base_op
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| FilterMap : ('a -> 'b option) -> ('a,'b) base_op
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| FlatMap : ('a -> 'b t) -> ('a,'b) base_op
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(* right-associativity *)
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let _compose f g = match f with
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| Compose (f1, f2) -> Compose (f1, Compose (f2, g))
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| _ -> Compose (f, g)
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let compose f g = _compose g f
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let (>>>) f g = _compose f g
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(* function composition *)
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let _compose_fun f g = fun x -> g (f x)
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(* associativity: put parenthesis on the right *)
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let rec _compose : type a b c. (a,b) op -> (b,c) op -> (a,c) op
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= fun f g -> match f with
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| Compose (f1, Id) -> Compose (f1, g)
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| Compose (f1, f2) -> Compose (f1, _compose f2 g)
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| Id -> g
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(* result of one step of optimization, indicates whether the object did
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change or not *)
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@ -91,10 +92,9 @@ module Make(C : COLLECTION) = struct
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let rec _optimize : type a b. (a,b) op -> (a,b) op
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= fun op -> match op with
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| Compose (a, b) ->
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let a' = _optimize a
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and b' = _optimize b in
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_optimize_rec (Compose (a', b'))
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| op -> op
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let b' = _optimize b in
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_optimize_rec (Compose (a, b'))
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| Id -> Id
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(* repeat optimization until a fixpoint is reached *)
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and _optimize_rec : type a b. (a,b) op -> (a,b) op
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= fun op -> match _optimize_head op with
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@ -102,24 +102,67 @@ module Make(C : COLLECTION) = struct
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| New op' -> _optimize_rec op'
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and _optimize_head : type a b. (a,b) op -> (a,b) op optim_result
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= function
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| Id -> Same Id
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| Compose (Map f, Compose (Map g, cont)) ->
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_new_compose (Map (fun x -> g (f x))) cont
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| Compose (Map f, Compose (Filter p, cont)) ->
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_new_compose
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(FilterMap (fun x -> let y = f x in if p y then Some y else None)) cont
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| Compose (Map f, Compose (FilterMap f', cont)) ->
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_new_compose
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(FilterMap (fun x -> f' (f x))) cont
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| Compose (Map f, Compose (FlatMap f', cont)) ->
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_new_compose
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(FlatMap (fun x -> f' (f x))) cont
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| Compose (Filter p, Compose (Filter p', cont)) ->
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_new_compose (Filter (fun x -> p x && p' x)) cont
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| Compose (Filter p, Compose (Map g, cont)) ->
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_new_compose
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(FilterMap (fun x -> if p x then Some (g x) else None)) cont
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| Compose (Filter p, Compose (Filter p', cont)) ->
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_new_compose (Filter (fun x -> p x && p' x)) cont
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| Compose (Filter p, Compose (FlatMap f, cont)) ->
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_new_compose (FlatMap (fun x -> if p x then f x else C.empty)) cont
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| op ->
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| Compose (Filter p, Compose (FilterMap f', cont)) ->
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_new_compose
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(FilterMap (fun x -> if p x then f' x else None)) cont
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| Compose (Filter p, Compose (FlatMap f', cont)) ->
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_new_compose
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(FlatMap (fun x -> if p x then f' x else C.empty)) cont
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| Compose (FilterMap f, Compose (FilterMap f', cont)) ->
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_new_compose
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(FilterMap
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(fun x -> match f x with None -> None | Some y -> f' y))
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cont
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| Compose (FilterMap f, Compose (Filter p, cont)) ->
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_new_compose
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(FilterMap
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(fun x -> match f x with
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| (Some y) as res when p y -> res
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| _ -> None))
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cont
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| Compose (FilterMap f, Compose (Map f', cont)) ->
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_new_compose
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(FilterMap
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(fun x -> match f x with
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| None -> None
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| Some y -> Some (f' y)))
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cont
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| Compose (FilterMap f, Compose (FlatMap f', cont)) ->
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_new_compose
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(FlatMap
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(fun x -> match f x with
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| None -> C.empty
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| Some y -> f' y))
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cont
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| (Compose _) as op ->
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Same op (* cannot optimize *)
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let apply op a =
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let rec _apply : type a b. (a,b) op -> a t -> b t
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= fun op a -> match op with
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| Compose (op1, op2) ->
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let a' = _apply op1 a in
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let a' = _apply_base op1 a in
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_apply op2 a'
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| Id -> a
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and _apply_base : type a b. (a,b) base_op -> a t -> b t
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= fun op a -> match op with
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| Map f -> C.map f a
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| Filter p -> C.filter p a
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| FlatMap f -> C.flat_map f a
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@ -133,9 +176,13 @@ module Make(C : COLLECTION) = struct
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(** {6 Combinators} *)
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let map f = Map f
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let filter p = Filter p
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let filter_map f = FilterMap f
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let flat_map f = FlatMap f
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let id = Id
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let map f = Compose (Map f, Id)
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let filter p = Compose (Filter p, Id)
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let filter_map f = Compose (FilterMap f, Id)
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let flat_map f = Compose (FlatMap f, Id)
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let compose f g = _compose g f
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let (>>>) f g = _compose f g
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end
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@ -53,6 +53,8 @@ module type S = sig
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(** {6 Combinators} *)
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val id : ('a, 'a) op
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val map : ('a -> 'b) -> ('a, 'b) op
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val filter : ('a -> bool) -> ('a,'a) op
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