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

2012-07-11

Returns a sequence that when enumerated returns at most N elements.

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

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

// Signature:
Seq.truncate : int -> seq<'T> -> seq<'T>

// Usage:
Seq.truncate count source

Parameters

count
Type: int

The maximum number of items to enumerate.
source
Type: seq<'T>

The input sequence.

Exceptions

Exception	Condition
ArgumentNullException	Thrown when the input sequence is null.

Return Value

The result sequence.

Remarks

This function is named Truncate 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.truncate and contrasts the behavior with Seq.take.

let mySeq = seq { for i in 1 .. 10 -> i*i }
let truncatedSeq = Seq.truncate 5 mySeq
let takenSeq = Seq.take 5 mySeq

let truncatedSeq2 = Seq.truncate 20 mySeq
let takenSeq2 = Seq.take 20 mySeq

let printSeq seq1 = Seq.iter (printf "%A ") seq1; printfn "" 

// Up to this point, the sequences are not evaluated. 
// The following code causes the sequences to be evaluated.
truncatedSeq |> printSeq
truncatedSeq2 |> printSeq
takenSeq |> printSeq
// The following line produces a run-time error (in printSeq):
takenSeq2 |> printSeq

1 4 9 16 25 
1 4 9 16 25 36 49 64 81 100 
1 4 9 16 25 
1 4 9 16 25 36 49 64 81 100

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

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