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

Article
02/04/2013

Compares two sequences using the given comparison function, element by element.

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

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

// Signature:
Seq.compareWith : ('T -> 'T -> int) -> seq<'T> -> seq<'T> -> int

// Usage:
Seq.compareWith comparer source1 source2

Parameters

comparer
Type: 'T -> 'T -> int

A function that takes an element from each sequence and returns an int. If it evaluates to a non-zero value iteration is stopped and that value is returned.
source1
Type: seq<'T>

The first input sequence.
source2
Type: seq<'T>

The second input sequence.

Exceptions

Exception	Condition
ArgumentNullException	Thrown when either of the input sequences is null.

Return Value

Returns the first non-zero result from the comparison function. If the end of a sequence is reached it returns a -1 if the first sequence is shorter and a 1 if the second sequence is shorter.

Remarks

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

Example

The following example demonstrates the use of Seq.compareWith to compare two sequences using a custom comparison function.

let sequence1 = seq { 1 .. 10 }
let sequence2 = seq { 10 .. -1 .. 1 }

// Compare two sequences element by element.
let compareSequences = Seq.compareWith (fun elem1 elem2 ->
    if elem1 > elem2 then 1
    elif elem1 < elem2 then -1
    else 0) 

let compareResult1 = compareSequences sequence1 sequence2
match compareResult1 with
| 1 -> printfn "Sequence1 is greater than sequence2."
| -1 -> printfn "Sequence1 is less than sequence2."
| 0 -> printfn "Sequence1 is equal to sequence2."
| _ -> failwith("Invalid comparison result.")

Sequence1 is less than sequence2.

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