Array.sumBy<'T,^U> Function (F#)

Returns the sum of the results generated by applying the function to each element of the array.

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

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

// Signature:
Array.sumBy : ('T -> ^U) -> 'T [] -> ^U (requires ^U with static member (+) and ^U with static member Zero)

// Usage:
Array.sumBy projection array


  • projection
    Type: 'T -> ^U

    The function to transform the array elements into the type to be summed.

  • array
    Type: 'T []

    The input array.

Return Value

The resulting sum.


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


The following code shows how to use Array.sumBy.

[| 1 .. 10 |]
|> Array.sumBy (fun x -> x * x)
|> printfn "Sum: %d"




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


Collections.Array Module (F#)

Microsoft.FSharp.Collections Namespace (F#)