Option.count<'T> Function (F#)
Evaluates the equivalent of Set.count for an option.
Namespace/Module Path: Microsoft.FSharp.Core.Option
Assembly: FSharp.Core (in FSharp.Core.dll)
// Signature:
count : 'T option -> int
// Usage:
count option
Parameters
option
Type: 'ToptionThe input option.
Return Value
A zero if the option is None, a one otherwise.
Remarks
The expression count inp evaluates to match inp with None -> 0 | Some _ -> 1.
This function is named Count 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 Option.count.
let opt1 = Some("test")
let opt2 = None
printfn "%A %A" (Option.count opt1) (Option.count opt2)
// Use Option.count to count the number of Some values in
// an array of options.
let getCount (array1 : int option array) =
Array.fold (fun state elem -> state + Option.count elem) 0 array1
let testArray1 = [| Some(10); None; Some(1); None; None; Some(56) |]
let testArray2 = [| for i in 1 .. 10 do if i % 2 = 0 then yield Some(i) else yield None |]
printfn "%d" <| getCount testArray1
printfn "%d" <| getCount testArray2
Output
1 0 3 5
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