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

Article
07/11/2012

Applies the given function to successive elements, returning the first result where function returns Some. If the function does not return Some for any element, then None is returned.

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

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

// Signature:
Array.tryPick : ('T -> 'U option) -> 'T [] -> 'U option

// Usage:
Array.tryPick chooser array

Parameters

chooser
Type: 'T -> 'U option

The function to transform the array elements into options.
array
Type: 'T[]

The input array.

Return Value

The first transformed element that has an option value of Some, or None if the function does not return Some for any element.

Remarks

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

Example

The following example demonstrates the use of Array.tryPick to attempt to locate an element that satisfies a condition, and also return some additional data about the element, in this case the square root and the cube root.

let findPerfectSquareAndCube array1 =
    let delta = 1.0e-10
    let isPerfectSquare (x:int) =
        let y = sqrt (float x)
        abs(y - round y) < delta
    let isPerfectCube (x:int) =
        let y = System.Math.Pow(float x, 1.0/3.0)
        abs(y - round y) < delta
    // intFunction : (float -> float) -> int -> int 
    // Allows the use of a floating point function with integers. 
    let intFunction function1 number = int (round (function1 (float number)))
    let cubeRoot x = System.Math.Pow(x, 1.0/3.0)
    // testElement: int -> (int * int * int) option 
    // Test an element to see whether it is a perfect square and a perfect 
    // cube, and, if so, return the element, square root, and cube root 
    // as an option value. Otherwise, return None. 
    let testElement elem = 
        if isPerfectSquare elem && isPerfectCube elem then
            Some(elem, intFunction sqrt elem, intFunction cubeRoot elem)
        else None
    match Array.tryPick testElement array1 with
    | Some (n, sqrt, cuberoot) -> printfn "Found an element %d with square root %d and cube root %d." n sqrt cuberoot
    | None -> printfn "Did not find an element that is both a perfect square and a perfect cube."

findPerfectSquareAndCube [| 1 .. 10 |]
findPerfectSquareAndCube [| 2 .. 100 |]
findPerfectSquareAndCube [| 100 .. 1000 |]
findPerfectSquareAndCube [| 1000 .. 10000 |]
findPerfectSquareAndCube [| 2 .. 50 |]

Found an element 1 with square root 1 and cube root 1.
Found an element 64 with square root 8 and cube root 4.
Found an element 729 with square root 27 and cube root 9.
Found an element 4096 with square root 64 and cube root 16.
Did not find an element that is both a perfect square and a perfect cube.

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

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