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Merge pull request dotnet#11 from liboz/manofstick
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seq.tail and a fix to takewhile to use avoidtailcall
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@manofstick
manofstick authored Oct 15, 2016
2 parents e51ff40 + 16b1ac4 commit ce17cf1
Showing 1 changed file with 34 additions and 17 deletions.
51 changes: 34 additions & 17 deletions src/fsharp/FSharp.Core/seq.fs
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Original file line number Diff line number Diff line change
Expand Up @@ -604,6 +604,10 @@ namespace Microsoft.FSharp.Collections
inherit SeqComponentFactory<'T,'T> ()
override __.Create<'V> (result:Result<'V>) (next:SeqComponent<'T,'V>) : SeqComponent<'T,'V> = upcast Take (count, result, next)

and TailFactory<'T> () =
inherit SeqComponentFactory<'T,'T> ()
override __.Create<'V> (_result:Result<'V>) (next:SeqComponent<'T,'V>) : SeqComponent<'T,'V> = upcast Tail<'T,'V> (next)

and TruncateFactory<'T> (count:int) =
inherit SeqComponentFactory<'T,'T> ()
override __.Create<'V> (result:Result<'V>) (next:SeqComponent<'T,'V>) : SeqComponent<'T,'V> = upcast Truncate (count, result, next)
Expand Down Expand Up @@ -876,7 +880,7 @@ namespace Microsoft.FSharp.Collections

override __.ProcessNext (input:'T) : bool =
if predicate input then
next.ProcessNext input
Helpers.avoidTailCall (next.ProcessNext input)
else
result.StopFurtherProcessing ()
false
Expand All @@ -888,6 +892,24 @@ namespace Microsoft.FSharp.Collections
result.Current <- input
true

and Tail<'T, 'V> (next:SeqComponent<'T,'V>) =
inherit SeqComponent<'T,'V>(next)

let mutable first = true

override __.ProcessNext (input:'T) : bool =
if first then
first <- false
false
else
Helpers.avoidTailCall (next.ProcessNext input)

interface ISeqComponent with
override this.OnComplete () =
if first then
invalidArg "source" (SR.GetString(SR.notEnoughElements))
(Helpers.upcastISeqComponent next).OnComplete ()

and Truncate<'T,'V> (truncateCount:int, result:Result<'V>, next:SeqComponent<'T,'V>) =
inherit SeqComponent<'T,'V>(next)

Expand Down Expand Up @@ -974,7 +996,7 @@ namespace Microsoft.FSharp.Collections
interface IEnumerable<'U> with
member this.GetEnumerator () : IEnumerator<'U> =
let result = Result<'U> ()
Helpers.upcastEnumerator (new Enumerator<'T,'U>(enumerable.GetEnumerator(), current.Create result (Tail result), result))
Helpers.upcastEnumerator (new Enumerator<'T,'U>(enumerable.GetEnumerator(), current.Create result (Tail<'U> result), result))

override __.Compose (next:SeqComponentFactory<'U,'V>) : IEnumerable<'V> =
Helpers.upcastEnumerable (new Enumerable<'T,'V>(enumerable, ComposedFactory.Combine current next))
Expand All @@ -985,7 +1007,7 @@ namespace Microsoft.FSharp.Collections
let enumerator = enumerable.GetEnumerator ()
let result = Result<'U> ()

let components = current.Create result (Tail result)
let components = current.Create result (Tail<'U> result)

let mutable state = initialState
while (not result.Halted) && (enumerator.MoveNext ()) do
Expand Down Expand Up @@ -1087,7 +1109,7 @@ namespace Microsoft.FSharp.Collections
interface IEnumerable<'U> with
member this.GetEnumerator () : IEnumerator<'U> =
let result = Result<'U> ()
Helpers.upcastEnumerator (new Enumerator<'T,'U>(array, current.Create result (Tail result), result))
Helpers.upcastEnumerator (new Enumerator<'T,'U>(array, current.Create result (Tail<'U> result), result))

override __.Compose (next:SeqComponentFactory<'U,'V>) : IEnumerable<'V> =
Helpers.upcastEnumerable (new Enumerable<'T,'V>(array, ComposedFactory.Combine current next))
Expand All @@ -1097,7 +1119,7 @@ namespace Microsoft.FSharp.Collections

let mutable idx = 0
let result = Result<'U> ()
let components = current.Create result (Tail result)
let components = current.Create result (Tail<'U> result)

let mutable state = initialState
while (not result.Halted) && (idx < array.Length) do
Expand Down Expand Up @@ -1137,7 +1159,7 @@ namespace Microsoft.FSharp.Collections
interface IEnumerable<'U> with
member this.GetEnumerator () : IEnumerator<'U> =
let result = Result<'U> ()
Helpers.upcastEnumerator (new Enumerator<'T,'U>(alist, current.Create result (Tail result), result))
Helpers.upcastEnumerator (new Enumerator<'T,'U>(alist, current.Create result (Tail<'U> result), result))

override __.Compose (next:SeqComponentFactory<'U,'V>) : IEnumerable<'V> =
Helpers.upcastEnumerable (new Enumerable<'T,'V>(alist, ComposedFactory.Combine current next))
Expand All @@ -1146,7 +1168,7 @@ namespace Microsoft.FSharp.Collections
let folder' = OptimizedClosures.FSharpFunc<_,_,_>.Adapt folder

let result = Result<'U> ()
let components = current.Create result (Tail result)
let components = current.Create result (Tail<'U> result)

let rec fold state lst =
match result.Halted, lst with
Expand Down Expand Up @@ -1187,7 +1209,7 @@ namespace Microsoft.FSharp.Collections
interface IEnumerable<'U> with
member this.GetEnumerator () : IEnumerator<'U> =
let result = Result<'U> ()
Helpers.upcastEnumerator (new Enumerator<'T,'U,'GeneratorState>(generator, state, current.Create result (Tail result), result))
Helpers.upcastEnumerator (new Enumerator<'T,'U,'GeneratorState>(generator, state, current.Create result (Tail<'U> result), result))

override this.Compose (next:SeqComponentFactory<'U,'V>) : IEnumerable<'V> =
Helpers.upcastEnumerable (new Enumerable<'T,'V,'GeneratorState>(generator, state, ComposedFactory.Combine current next))
Expand All @@ -1196,7 +1218,7 @@ namespace Microsoft.FSharp.Collections
let folder' = OptimizedClosures.FSharpFunc<_,_,_>.Adapt folder

let result = Result<'U> ()
let components = current.Create result (Tail result)
let components = current.Create result (Tail<'U> result)

let rec fold state current =
match result.Halted, generator current with
Expand Down Expand Up @@ -1272,7 +1294,7 @@ namespace Microsoft.FSharp.Collections
interface IEnumerable<'U> with
member this.GetEnumerator () : IEnumerator<'U> =
let result = Result<'U> ()
Helpers.upcastEnumerator (new Enumerator<'T,'U>(count, f, current.Create result (Tail result), result))
Helpers.upcastEnumerator (new Enumerator<'T,'U>(count, f, current.Create result (Tail<'U> result), result))

override this.Compose (next:SeqComponentFactory<'U,'V>) : IEnumerable<'V> =
Helpers.upcastEnumerable (new Enumerable<'T,'V>(count, f, ComposedFactory.Combine current next))
Expand All @@ -1281,7 +1303,7 @@ namespace Microsoft.FSharp.Collections
let folder' = OptimizedClosures.FSharpFunc<_,_,_>.Adapt folder

let result = Result<'U> ()
let components = current.Create result (Tail result)
let components = current.Create result (Tail<'U> result)

let mutable idx = -1
let terminatingIdx = getTerminatingIdx count
Expand Down Expand Up @@ -2253,12 +2275,7 @@ namespace Microsoft.FSharp.Collections

[<CompiledName("Tail")>]
let tail (source: seq<'T>) =
checkNonNull "source" source
seq { use e = source.GetEnumerator()
if not (e.MoveNext()) then
invalidArg "source" (SR.GetString(SR.notEnoughElements))
while e.MoveNext() do
yield e.Current }
source |> seqFactory (SeqComposer.TailFactory ())

[<CompiledName("Last")>]
let last (source : seq<_>) =
Expand Down

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