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[WIP - discussion] - Alternate Method of Seq.map chaining #1528

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[WIP - discussion] - Alternate Method of Seq.map chaining #1528

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32 changes: 21 additions & 11 deletions src/fsharp/FSharp.Core/seq.fs
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Original file line number Diff line number Diff line change
Expand Up @@ -107,18 +107,28 @@ namespace Microsoft.FSharp.Collections
member this.Reset() = noReset()
interface System.IDisposable with
member this.Dispose() = this.Dispose()

[<AbstractClass>]
type MapSingleAbstractEnumerator<'T> () =
inherit MapEnumerator<'T> ()
abstract member Map: ('T -> 'TResult) -> IEnumerator<'TResult>

let map f (e : IEnumerator<_>) : IEnumerator<_>=
upcast
{ new MapEnumerator<_>() with
member this.DoMoveNext (curr : byref<_>) =
if e.MoveNext() then
curr <- (f e.Current)
true
else
false
member this.Dispose() = e.Dispose()
}
type MapSingleEnumerator<'T0, 'T1> (e: IEnumerator<'T0>, f: 'T0 -> 'T1) =
inherit MapSingleAbstractEnumerator<'T1> ()
override this.DoMoveNext (curr : byref<_>) =
if e.MoveNext() then
curr <- f e.Current
true
else
false
override this.Dispose() = e.Dispose()
override this.Map (g: 'T1 -> 'T2) = new MapSingleEnumerator<'T0, 'T2>(e, f >> g) :> IEnumerator<'T2>

let map f (e : IEnumerator<_>) : IEnumerator<_> =
match e with
| :? MapSingleAbstractEnumerator<'TSource> as i ->
i.Map(f)
| _ -> new MapSingleEnumerator<'TSource, 'TResult>(e, f) :> IEnumerator<'TResult>

let mapi f (e : IEnumerator<_>) : IEnumerator<_> =
let f = OptimizedClosures.FSharpFunc<_,_,_>.Adapt(f)
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