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

Article
07/11/2012

Looks up an element in the map. If no binding exists in the map, raises KeyNotFoundException.

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

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

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

// Usage:
Map.find key table

Parameters

key
Type: 'Key

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

The input map.

Exceptions

Exception	Condition
KeyNotFoundException	Thrown when the key does not exist in the map.

Return Value

The value mapped to the given key.

Remarks

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

Example

The following examples shows how to use Map.filter.

let findAndPrint key map =
    printfn "With key %d, found value %A." key (Map.find key map)
let map1 = Map.ofList [ (1, "one"); (2, "two"); (3, "three") ]
let map2 = Map.ofList [ for i in 1 .. 10 -> (i, i*i) ]
try
    findAndPrint 1 map1
    findAndPrint 2 map1
    findAndPrint 3 map2
    findAndPrint 5 map2
    // The key is not in the map, so this throws an exception.
    findAndPrint 0 map2
with
     :? System.Collections.Generic.KeyNotFoundException as e -> printfn "%s" e.Message

Output

With key 1, found value "one".
With key 2, found value "two".
With key 3, found value 9.
With key 5, found value 25.
The given key was not present in the dictionary.

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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