Seq.readonly<'T> Function (F#)
Creates a new sequence object that delegates to the given sequence object. This ensures the original sequence cannot be rediscovered and mutated by a type cast. For example, if given an array the returned sequence will return the elements of the array, but you cannot cast the returned sequence object to an array.
Namespace/Module Path: Microsoft.FSharp.Collections.Seq
Assembly: FSharp.Core (in FSharp.Core.dll)
// Signature:
Seq.readonly : seq<'T> -> seq<'T>
// Usage:
Seq.readonly source
Parameters
source
Type: seq<'T>The input sequence.
Exceptions
Exception |
Condition |
|---|---|
Thrown when the input sequence is null. |
Return Value
The result sequence.
Remarks
This function is named ReadOnly 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 uses Seq.readonly to create an immutable view of a mutable array.
type ArrayContainer(start, finish) =
let internalArray = [| start .. finish |]
member this.RangeSeq = Seq.readonly internalArray
member this.RangeArray = internalArray
let newArray = new ArrayContainer(1, 10)
let rangeSeq = newArray.RangeSeq
let rangeArray = newArray.RangeArray
// These lines produce an error:
//let myArray = rangeSeq :> int array
//myArray.[0] <- 0
// The following line does not produce an error.
// It does not preserve encapsulation.
rangeArray.[0] <- 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