List.sumBy<'T,^U> Function (F#)
Returns the sum of the results generated by applying the function to each element of the list.
Namespace/Module Path: Microsoft.FSharp.Collections.List
Assembly: FSharp.Core (in FSharp.Core.dll)
// Signature: List.sumBy : ('T -> ^U) -> 'T list -> ^U (requires ^U with static member (+) and ^U with static member Zero) // Usage: List.sumBy projection list
projection Type: 'T -> ^U
A function that transforms the list elements into the type to be summed.
list Type: 'Tlist
The input list.
The sum of the results of applying the projection function to each element of the list.
May throw an OverflowException due to arithmetic overflows.
The results are summed using the
checked + operator and
Zero property associated with the summed type.
This function is named
SumBy in compiled assemblies. If you are accessing the function from a .NET language other than F#, or through reflection, use this name.
// Compute the sum of the first 10 integers by using List.sum. let sum1 = List.sum [1 .. 10] // Compute the sum of the squares of the elements of a list by using List.sumBy. let sum2 = List.sumBy (fun elem -> elem*elem) [1 .. 10] // Compute the average of the elements of a list by using List.average. let avg1 = List.average [0.0; 1.0; 1.0; 2.0] printfn "%f" avg1
Windows 8, Windows 7, Windows Server 2012, Windows Server 2008 R2
F# Core Library Versions
Supported in: 2.0, 4.0, Portable