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List.pick<'T,'U> Function (F#)

Applies the given function to successive elements, returning the first result where function returns Some for some value. If no such element exists then this function raises KeyNotFoundException.

Namespace/Module Path: Microsoft.FSharp.Collections.List

Assembly: FSharp.Core (in FSharp.Core.dll)

// Signature:
List.pick : ('T -> 'U option) -> 'T list -> 'U

// Usage:
List.pick chooser list

chooser

Type: 'T -> 'U option

The function to generate options from the elements.

list

Type: 'T list

The input list.

Exception

Condition

KeyNotFoundException

Thrown when a matching element is not found or when the list is empty.

The first resulting value where Some is returned.

This function is named Pick in compiled assemblies. If you are accessing the function from a .NET language other than F#, or through reflection, use this name.

The following code example illustrates the use of List.pick.


let valuesList = [ ("a", 1); ("b", 2); ("c", 3) ]

let resultPick = List.pick (fun elem ->
                    match elem with
                    | (value, 2) -> Some value
                    | _ -> None) valuesList
printfn "%A" resultPick


Output

"b"

Windows 7, Windows Vista SP2, Windows XP SP3, Windows XP x64 SP2, Windows Server 2008 R2, Windows Server 2008 SP2, Windows Server 2003 SP2

F# Runtime

Supported in: 2.0, 4.0

Silverlight

Supported in: 3

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