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

Den Delimarsky|Last Updated: 8/18/2017
1 Contributor

Generates a new sequence which, when iterated, will return successive elements by calling the given function, up to the given count.

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

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


// Signature:
Seq.init : int -> (int -> 'T) -> seq<'T>

// Usage:
Seq.init count initializer


count Type: int

The maximum number of items to generate for the sequence.

initializer Type: int-> 'T

A function that generates an item in the sequence from a given index.


ArgumentExceptionThrown when count is negative.

Return Value

The result sequence.


Each element is saved after its initialization. The function is passed the index of the item being generated.

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

Thread Safety

The returned sequence may be passed between threads safely. However, individual IEnumerator values generated from the returned sequence should not be accessed concurrently.


The following example demonstrates the use of Seq.init to create a sequence of the first five multiples of 10.

let seqFirst5MultiplesOf10 = Seq.init 5 (fun n -> n * 10)
Seq.iter (fun elem -> printf "%d " elem) seqFirst5MultiplesOf10
0 10 20 30 40


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#)

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