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Array.filter<'T> Function (F#)

Den Delimarsky|Last Updated: 8/18/2017
1 Contributor

Returns a new collection containing only the elements of the collection for which the given predicate returns true.

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

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


// Signature:
Array.filter : ('T -> bool) -> 'T [] -> 'T []

// Usage:
Array.filter predicate array


predicate Type: 'T ->bool

The function to test the input elements.

array Type: 'T[]

The input array.

Return Value

An array containing the elements for which the given predicate returns true.


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


The following example shows how to use Array.filter to select elements from an array.

let names = [|"Bob"; "Ann"; "Stephen"; "Vivek"; "Fred"; "Kim"; "Brian"; "Ling"; "Jane"; "Jonathan"|]
let longNames = names |> Array.filter (fun x -> x.Length > 4)

printfn "names = %A\n" names
printfn "longNames = %A" longNames
names = [|"Bob"; "Ann"; "Stephen"; "Vivek"; "Fred"; "Kim"; "Brian"; "Ling"; "Jane"; "Jonathan"|]

longNames = [|"Stephen"; "Vivek"; "Brian"; "Jonathan"|]


Windows 8, Windows 7, Windows Server 2012, Windows Server 2008 R2

Version Information

F# Core Library Versions

Supported in: 2.0, 4.0, Portable

See Also

Collections.Array Module (F#)

Microsoft.FSharp.Collections Namespace (F#)

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