Seq.distinct<'T> Function (F#)

Article
02/04/2013

Returns a sequence that contains no duplicate entries according to generic hash and equality comparisons on the entries. If an element occurs multiple times in the sequence then the later occurrences are discarded.

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

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

// Signature:
Seq.distinct : seq<'T> -> seq<'T> (requires equality)

// Usage:
Seq.distinct source

Parameters

source
Type: seq<'T>

The input sequence.

Exceptions

Exception	Condition
ArgumentNullException	Thrown when the input sequence is null.

Return Value

The result sequence.

Remarks

This function is named Distinct 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 Seq.distinct. The example generates the binary representation of a number as a sequence. It then determines that the only unique numbers are 0 and 1.

let binary n =
    let rec generateBinary n =
        if (n / 2 = 0) then [n]
        else (n % 2) :: generateBinary (n / 2)
    generateBinary n |> List.rev |> Seq.ofList

printfn "%A" (binary 1024)

let resultSequence = Seq.distinct (binary 1024)
printfn "%A" resultSequence

[1; 0; 0; 0; 0; 0; 0; 0; 0; 0; 0]
seq [1; 0]

Platforms

Windows 7, Windows Vista SP2, Windows XP SP3, Windows XP x64 SP2, Windows Server 2008 R2, Windows Server 2008 SP2, Windows Server 2003 SP2

Version Information

F# Runtime

Supported in: 2.0, 4.0

Silverlight

Supported in: 3

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