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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

reduction

Type: 'T -> 'T -> 'T

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

array

Type: 'T []

The input array.

Exception

Condition

ArgumentException

Thrown when the input array is empty.

The final result of the reductions.

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.

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

Windows 8, Windows 7, Windows Server 2012, Windows Server 2008 R2

F# Core Library Versions

Supported in: 2.0, 4.0, Portable

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