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

Parameters

• predicate
  Type: 'T ->bool

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

• source
  Type: seq<'T>

  The input sequence.

Exceptions

Return Value

The result sequence.

Remarks

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.

Example

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

Platforms

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

Reference

Collections.Seq Module (F#)

Microsoft.FSharp.Collections Namespace (F#)