Table of contents
TOC
Collapse the table of content
Expand the table of content

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

Den Delimarsky|Last Updated: 7/25/2016
|
1 Contributor

Returns the first element of the sequence.

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

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

Syntax

// Signature:
Seq.head : seq<'T> -> 'T

// Usage:
Seq.head source

Parameters

source Type: seq<'T>

The input sequence.

Exceptions

ExceptionCondition
ArgumentExceptionThrown when the input sequence is empty.
ArgumentNullExceptionThrown when the input sequence is null.

Return Value

The first element of the sequence.

Remarks

The first element of the source sequence is evaluated at each call. To avoid this reevaluation, you can create a cached version of a sequence by calling Seq.cache.

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

Example


    let headItem = Seq.head [| 1 .. 10 |]
    printfn "%d" headItem

Output

1

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

Collections.Seq Module (F#)

Microsoft.FSharp.Collections Namespace (F#)

© 2016 Microsoft