List.iteri<'T> Function (F#)

Applies the given function to each element of the collection. The integer passed to the function indicates the index of element.

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

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

// Signature:
List.iteri : (int -> 'T -> unit) -> 'T list -> unit

// Usage:
List.iteri action list


  • action
    Type: int -> 'T -> unit

    The function to apply to the elements of the list along with their index.

  • list
    Type: 'T list

    The input list.


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


The following example demonstrates the use of List.iteri.

let data = ["Cats";"Dogs";"Mice";"Elephants"]
data |> List.iteri (fun i x -> printfn "item %d: %s" i x)
item 0: Cats
item 1: Dogs
item 2: Mice
item 3: Elephants


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


Supported in: 3

See Also


Collections.List Module (F#)

Microsoft.FSharp.Collections Namespace (F#)