type U =
| A of int
| B of float
| C of string
let UFormat =
(
UnionCase A IntFormat <<
UnionCase B FloatFormat <<
UnionCase C StringFormat
)
|> Union (fun a b c x ->
match x with
| A x -> a x
| B x -> b x
| C x -> c x)
type R =
{
A : int
B : float
C : string
}
let RFormat : Format<R> =
(
RecordField (fun r -> r.A) IntFormat <<
RecordField (fun r -> r.B) FloatFormat <<
RecordField (fun r -> r.C) StringFormat
)
|> Record (fun a b c -> { A = a; B = b; C = c })
With some simplifications, here is the code:
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| open System.IO | |
| type Format<'T> = | |
| { | |
| Read : BinaryReader -> 'T | |
| Write : BinaryWriter -> 'T -> unit | |
| } | |
| (* Unions *) | |
| type UnionPart<'X,'U> = | |
| { | |
| R : list<BinaryReader -> 'U> | |
| W : 'X -> 'U -> BinaryWriter -> unit | |
| } | |
| let UnionCase (ctor: 'C -> 'U) (fmt: Format<'C>) | |
| (part: UnionPart<'X,'U>) : UnionPart<('C -> unit) -> 'X,'U> = | |
| let tag = char part.R.Length | |
| let write (w: BinaryWriter) x = | |
| w.Write(tag) | |
| fmt.Write w x | |
| { | |
| R = (fmt.Read >> ctor) :: part.R | |
| W = fun f u w -> part.W (f (write w)) u w | |
| } | |
| let private unionEnd<'U> : UnionPart<('U -> unit),'U> = | |
| { | |
| R = [] | |
| W = fun f u w -> f u | |
| } | |
| let Union proof f = | |
| let part = f unionEnd | |
| let rs = Array.rev (List.toArray part.R) | |
| { | |
| Read = fun r -> | |
| let tag = int (r.ReadChar()) | |
| rs.[tag] r | |
| Write = fun w x -> part.W proof x w | |
| } | |
| (* Records *) | |
| type RecordPart<'X,'R> = | |
| { | |
| R : 'X -> BinaryReader -> 'R | |
| W : list<BinaryWriter -> 'R -> unit> | |
| } | |
| let RecordField<'F,'U,'X> (proj: 'U -> 'F) (fmt: Format<'F>) (part: RecordPart<'X,'U>) : RecordPart<'F -> 'X, 'U> = | |
| { | |
| R = fun x r -> part.R (x (fmt.Read(r))) r | |
| W = (fun w x -> fmt.Write w (proj x)) :: part.W | |
| } | |
| let private recordEnd<'T> : RecordPart<'T,'T> = | |
| { | |
| R = fun r _ -> r | |
| W = [] | |
| } | |
| let Record proof f = | |
| let x = f recordEnd | |
| let ws = List.toArray x.W | |
| { | |
| Read = x.R proof | |
| Write = fun w x -> for f in ws do f w x | |
| } | |
| (* Scalars *) | |
| let IntFormat : Format<int> = | |
| { | |
| Read = fun r -> r.ReadInt32() | |
| Write = fun w x -> w.Write(x) | |
| } | |
| let FloatFormat : Format<float> = | |
| { | |
| Read = fun r -> r.ReadDouble() | |
| Write = fun w x -> w.Write(x) | |
| } | |
| let StringFormat : Format<string> = | |
| { | |
| Read = fun r -> r.ReadString() | |
| Write = fun w x -> w.Write(x) | |
| } |
