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

Applies a function to each element of the collection, threading an accumulator argument through the computation. This function first applies the function to the first two elements of the list. Then, it passes this result into the function along with the third element and so on. Finally, it returns the final result. If the input function is f and the elements are i0...iN, then it computes f (... (f i0 i1) i2 ...) iN.

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

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

// Signature:
List.reduce : ('T -> 'T -> 'T) -> 'T list -> 'T

// Usage:
List.reduce reduction list

Parameters

• reduction
  Type: 'T -> 'T -> 'T

  The function to reduce two list elements to a single element.

• list
  Type: 'T list

  The input list.

Exceptions

Exception	Condition
ArgumentException	Thrown when the list is empty.

Return Value

The final reduced value.

Remarks

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

Example

The following code example illustrates the use of List.reduce.

let sumAList list =
    try
        List.reduce (fun acc elem -> acc + elem) list
    with
       | :? System.ArgumentException as exc -> 0

let resultSum = sumAList [2; 4; 10]
printfn "%d " resultSum

Output

16

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

See Also

Reference

Collections.List Module (F#)

Microsoft.FSharp.Collections Namespace (F#)