Recursor

A sugar around IEnumerator<'a> to make it nicer to use with recursive functions

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module Recursor

type Recursor<'a> (enumerable:System.Collections.Generic.IEnumerable<'a>) =
    let enumerator = enumerable.GetEnumerator ()

    let mutable moreData = enumerator.MoveNext ()

    member __.TryGetValue ([<System.Runtime.InteropServices.OutAttribute>] out:byref<'a>) =
        if moreData then
            out <- enumerator.Current
            true
        else
            false

    member this.Next =
        moreData <- enumerator.MoveNext ()
        this

type System.Collections.Generic.IEnumerable<'a> with
    member this.Recursor = Recursor this
    
// example
let inline sum (e:System.Collections.Generic.IEnumerable<int>) =
    let rec f (cursor:Recursor<int>) total =
        match cursor.TryGetValue () with
        | false, _-> total
        | true, value -> f cursor.Next (total+value)

    f e.Recursor 0

module Recursor

Multiple items
type Recursor<'a> =
  new : enumerable:IEnumerable<'a> -> Recursor<'a>
  member TryGetValue : out:byref<'a> -> bool
  member Next : Recursor<'a>

Full name: Recursor.Recursor<_>

--------------------
new : enumerable:System.Collections.Generic.IEnumerable<'a> -> Recursor<'a>

val enumerable : System.Collections.Generic.IEnumerable<'a>

namespace System

namespace System.Collections

namespace System.Collections.Generic

type IEnumerable<'T> =
member GetEnumerator : unit -> IEnumerator<'T>

Full name: System.Collections.Generic.IEnumerable<_>

val enumerator : System.Collections.Generic.IEnumerator<'a>

System.Collections.Generic.IEnumerable.GetEnumerator() : System.Collections.Generic.IEnumerator<'a>

val mutable moreData : bool

System.Collections.IEnumerator.MoveNext() : bool

member Recursor.TryGetValue : out:byref<'a> -> bool

Full name: Recursor.Recursor`1.TryGetValue

namespace System.Runtime

namespace System.Runtime.InteropServices

Multiple items
type OutAttribute =
inherit Attribute
new : unit -> OutAttribute

Full name: System.Runtime.InteropServices.OutAttribute

--------------------
System.Runtime.InteropServices.OutAttribute() : unit

val out : byref<'a>

type byref<'T> = (# "<Common IL Type Omitted>" #)

Full name: Microsoft.FSharp.Core.byref<_>

property System.Collections.Generic.IEnumerator.Current: 'a

val this : Recursor<'a>

member Recursor.Next : Recursor<'a>

Full name: Recursor.Recursor`1.Next

val this : System.Collections.Generic.IEnumerable<'T>

Multiple items
member System.Collections.Generic.IEnumerable.Recursor : Recursor<'T>

Full name: Recursor.Recursor

--------------------
type Recursor<'a> =
  new : enumerable:IEnumerable<'a> -> Recursor<'a>
  member TryGetValue : out:byref<'a> -> bool
  member Next : Recursor<'a>

Full name: Recursor.Recursor<_>

--------------------
new : enumerable:System.Collections.Generic.IEnumerable<'a> -> Recursor<'a>

val sum : e:System.Collections.Generic.IEnumerable<int> -> int

Full name: Recursor.sum

val e : System.Collections.Generic.IEnumerable<int>

Multiple items
val int : value:'T -> int (requires member op_Explicit)

Full name: Microsoft.FSharp.Core.Operators.int

--------------------
type int = int32

Full name: Microsoft.FSharp.Core.int

--------------------
type int<'Measure> = int

Full name: Microsoft.FSharp.Core.int<_>

val f : (Recursor<int> -> int -> int)

val cursor : Recursor<int>

val total : int

member Recursor.TryGetValue : out:byref<'a> -> bool

val value : int

property Recursor.Next: Recursor<int>

property System.Collections.Generic.IEnumerable.Recursor: Recursor<'T>

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More information

Link:	http://fssnip.net/7Uq
Posted:	6 years ago
Author:	manofstick
Tags:	recursion , seq