Map.containsKey<'Key,'T> Function (F#)

Article
07/11/2012

Tests if an element is in the domain of the map.

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

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

// Signature:
Map.containsKey : 'Key -> Map<'Key,'T> -> bool (requires comparison)

// Usage:
Map.containsKey key table

Parameters

key
Type: 'Key

The input key.
table
Type: Map<'Key,'T>

The input map.

Return Value

true if the map contains the key.

Remarks

This function is named ContainsKey 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 shows how to use Map.containsKey.

let map1 = Map.ofList [ (1, "one"); (2, "two"); (3, "three") ]
let findKeyAndPrint key map =
    if (Map.containsKey key map) then
        printfn "The specified map contains the key %d." key
    else
        printfn "The specified map does not contain the key %d." key
findKeyAndPrint 1 map1
findKeyAndPrint 0 map1

Output

The specified map contains the key 1.
The specified map does not contain the key 0.

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