Array.scan<'T,'State> Function (F#)

Article
04/28/2015

Like Array.fold, but returns the intermediate and final results.

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

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

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

// Usage:
Array.scan folder state array

Parameters

folder
Type: 'State -> 'T -> 'State

The function to update the state given the input elements.
state
Type: 'State

The initial state.
array
Type: 'T[]

The input array.

Return Value

The array of state values.

Remarks

This function is named Scan 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 illustrates the use of Array.scan.

let initialBalance = 1122.73
let transactions = [| -100.00; +450.34; -62.34; -127.00; -13.50; -12.92 |]
let balances =
    Array.scan (fun balance transactionAmount -> balance + transactionAmount) initialBalance transactions
printfn "Initial balance:\n $%10.2f" initialBalance
printfn "Transaction   Balance" 
for i in 0 .. Array.length transactions - 1 do
    printfn "$%10.2f $%10.2f" transactions.[i] balances.[i]
printfn "Final balance:\n $%10.2f" balances.[ Array.length balances - 1]

Output

Initial balance:
 $   1122.73
Transaction   Balance
$   -100.00 $   1122.73
$    450.34 $   1022.73
$    -62.34 $   1473.07
$   -127.00 $   1410.73
$    -13.50 $   1283.73
$    -12.92 $   1270.23
Final balance:
 $   1257.31

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