Array.reduceBack<'T> Function (F#)

Applies a function to each element of the array, threading an accumulator argument through the computation. If the input function is f and the elements are i0...iN then computes f i0 (...(f iN-1 iN)). Raises ArgumentException if the array has size zero.

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

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

// Signature:
Array.reduceBack : ('T -> 'T -> 'T) -> 'T [] -> 'T

// Usage:
Array.reduceBack reduction array

Parameters

• reduction
  Type: 'T -> 'T -> 'T

  The function to reduce a pair of elements to a single element.

• array
  Type: 'T[]

  The input array.

Exceptions

Return Value

The final result of the reductions.

Remarks

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

Example

The following code example compares Array.reduce and Array.reduceBack.

// Computes ((1 - 2) - 3) - 4 = -8
Array.reduce (fun elem acc -> elem - acc) [| 1; 2; 3; 4 |]
|> printfn "%A" 
// Computes 1 - (2 - (3 - 4)) = -2
Array.reduceBack (fun elem acc -> elem - acc) [| 1; 2; 3; 4 |]
|> printfn "%A"

Output

-8
-2

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.Array Module (F#)

Microsoft.FSharp.Collections Namespace (F#)