# Seq.iter2<'T1,'T2> Function (F#)

Visual Studio 2013

Applies the given function to two collections simultaneously. If one sequence is shorter than the other then the remaining elements of the longer sequence are ignored.

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

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

```// Signature:
Seq.iter2 : ('T1 -> 'T2 -> unit) -> seq<'T1> -> seq<'T2> -> unit

// Usage:
Seq.iter2 action source1 source2
```

## Parameters

action

Type: 'T1 -> 'T2 -> unit

A function to apply to each pair of elements from the input sequences.

source1

Type: seq<'T1>

The first input sequence.

source2

Type: seq<'T2>

The second input sequence.

## Exceptions

Exception

Condition

Thrown when either of the input sequences is null.

## Remarks

This function is named Iterate2 in compiled assemblies. If you are accessing the function from a .NET language other than F#, or through reflection, use this name.

## Example

The following code shows how to use Seq.iter2 and compares its behavior to related functions.

```let seq1 = [1; 2; 3]
let seq2 = [4; 5; 6]
Seq.iter (fun x -> printfn "Seq.iter: element is %d" x) seq1
Seq.iteri(fun i x -> printfn "Seq.iteri: element %d is %d" i x) seq1
Seq.iter2 (fun x y -> printfn "Seq.iter2: elements are %d %d" x y) seq1 seq2
```

Output

```Seq.iter: element is 1
Seq.iter: element is 2
Seq.iter: element is 3
Seq.iteri: element 0 is 1
Seq.iteri: element 1 is 2
Seq.iteri: element 2 is 3
Seq.iter2: elements are 1 4
Seq.iter2: elements are 2 5
Seq.iter2: elements are 3 6```

## 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