Seq.collect<'T,'Collection,'U> Function (F#)

Applies the given function to each element of the sequence and concatenates all the results.

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

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

// Signature:
Seq.collect : ('T -> 'Collection) -> seq<'T> -> seq<'U> (requires 'Collection :> seq<'U>)

// Usage:
Seq.collect mapping source

Parameters

• mapping
  Type: 'T -> 'Collection

  A function to transform elements of the input sequence into the sequences that are concatenated.

• source
  Type: seq<'T>

  The input sequence.

Exceptions

Return Value

The result sequence.

Remarks

The sequence is evaluated lazily. Therefore, effects are delayed until it is enumerated.

This function is named Collect 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 demonstrates the use of Seq.collect.

let addNegations seq1 =
   Seq.collect (fun x -> seq { yield x; yield -x }) seq1
   |> Seq.sort
addNegations [ 1 .. 4 ] |> Seq.iter (fun elem -> printf "%d " elem)
printfn ""
addNegations [| 0; -4; 2; -12 |] |> Seq.iter (fun elem -> printf "%d " elem)

Output

-4 -3 -2 -1 1 2 3 4 
-12 -4 -2 0 0 2 4 12

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

See Also

Reference

Collections.Seq Module (F#)

Microsoft.FSharp.Collections Namespace (F#)