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Merged
merged 2 commits into from
Feb 21, 2023
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+ functions as Alternatives (conditionally) #535

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+ functions as Alternatives (conditionally)
gusty Feb 19, 2023
ec5b212
Update docs
gusty Feb 21, 2023
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3 changes: 2 additions & 1 deletion docsrc/content/abstraction-alternative.fsx
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Expand Up @@ -59,6 +59,7 @@ From .Net/F#
- ``option<'T>``
- ``array<'T>``
- ``seq<'T>``
- ``'T -> 'Alternative``

From F#+

Expand Down Expand Up @@ -157,4 +158,4 @@ let r6 = map string (Just 6)
// But not always the Monoidal behaviour is the same

let r3 = Some 2 ++ Some 1 // addition => Some 3
let r2 = Some 2 <|> Some 1 // first success => Some 2
let r2 = Some 2 <|> Some 1 // first success => Some 2
6 changes: 5 additions & 1 deletion src/FSharpPlus/Control/Alternative.fs
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Expand Up @@ -24,14 +24,16 @@ type Empty =
static member Empty ([<Optional>]_output: option<'T> , [<Optional>]_mthd: Empty ) = None : option<'T>
static member Empty ([<Optional>]_output: voption<'T> , [<Optional>]_mthd: Empty ) = ValueNone : voption<'T>
static member Empty ([<Optional>]_output: list<'T> , [<Optional>]_mthd: Empty ) = [ ] : list<'T>
static member Empty ([<Optional>]_output: 'T [] , [<Optional>]_mthd: Empty ) = [||] : 'T []
static member Empty ([<Optional>]_output: 'T [] , [<Optional>]_mthd: Empty ) = [||] : 'T []

static member inline Invoke () : '``Alternative<'T>`` =
let inline call (mthd: ^M, output: ^R) = ((^M or ^R) : (static member Empty : _*_ -> _) output, mthd)
call (Unchecked.defaultof<Empty>, Unchecked.defaultof<'``Alternative<'T>``> )

static member inline InvokeOnInstance () : '``Alternative<'T>`` = (^``Alternative<'T>`` : (static member Empty : ^``Alternative<'T>``) ()) : '``Alternative<'T>``

type Empty with
static member inline Empty ([<Optional>]_output: 'R -> '``Alternative<'T>``, [<Optional>]_mthd: Empty) = (fun _ -> Empty.Invoke ()) : 'R -> '``Alternative<'T>``

type Append =
inherit Default1
Expand All @@ -53,6 +55,8 @@ type Append =
let inline call (mthd: ^M, input1: ^I, input2: ^I) = ((^M or ^I) : (static member ``<|>`` : _*_*_ -> _) input1, input2, mthd)
call (Unchecked.defaultof<Append>, x, y)

type Append with
static member inline ``<|>`` (x: 'R -> '``Alt<'T>`` , y , [<Optional>]_mthd: Append ) = fun r -> Append.Invoke (x r) (y r)


type IsAltLeftZero =
Expand Down