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Seq.takeWhile<'T> Function (F#)

Returns a sequence that, when iterated, yields elements of the underlying sequence while the given predicate returns true, and then returns no further elements.

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

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

// Signature:
Seq.takeWhile : ('T -> bool) -> seq<'T> -> seq<'T>

// Usage:
Seq.takeWhile predicate source


Type: 'T -> bool

A function that evaluates to false when no more items should be returned.


Type: seq<'T>

The input sequence.




Thrown when the input sequence is null.

The result sequence.

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

The following example demonstrates the use of Seq.takeWhile. The sequence contains squares of integers that are less than 10.

let mySeq = seq { for i in 1 .. 10 -> i*i }
let printSeq seq1 = Seq.iter (printf "%A ") seq1; printfn "" 
let mySeqLessThan10 = Seq.takeWhile (fun elem -> elem < 10) mySeq
mySeqLessThan10 |> printSeq
1 4 9

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

F# Core Library Versions

Supported in: 2.0, 4.0, Portable

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