Seq.head<'T> Function (F#)
Returns the first element of the sequence.
Namespace/Module Path: Microsoft.FSharp.Collections.Seq
Assembly: FSharp.Core (in FSharp.Core.dll)
// Signature:
Seq.head : seq<'T> -> 'T
// Usage:
Seq.head source
Parameters
source
Type: seq<'T>The input sequence.
Exceptions
Exception |
Condition |
|---|---|
Thrown when the input does not have any elements. |
|
Thrown 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
The following code shows how to use Seq.head.
let headItem = Seq.head [| 1 .. 10 |]
printfn "%d" headItem
Output
1
Platforms
Windows 7, Windows Vista SP2, Windows XP SP3, Windows XP x64 SP2, Windows Server 2008 R2, Windows Server 2008 SP2, Windows Server 2003 SP2
Version Information
F# Runtime
Supported in: 2.0, 4.0
Silverlight
Supported in: 3