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)
Syntax
// Signature:
Seq.head : seq<'T> -> 'T
// Usage:
Seq.head source
Parameters
source Type: seq<'T>
The input sequence.
Exceptions
Exception | Condition |
---|---|
ArgumentException | Thrown when the input sequence is empty. |
ArgumentNullException | 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
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