Seq.exists2<'T1,'T2> Function (F#)

Tests if any pair of corresponding elements of the input sequences satisfies the given predicate.

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

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

// Signature:
Seq.exists2 : ('T1 -> 'T2 -> bool) -> seq<'T1> -> seq<'T2> -> bool

// Usage:
Seq.exists2 predicate source1 source2


  • predicate
    Type: 'T1 -> 'T2 -> bool

    A function to test each pair of items from the input sequences.

  • source1
    Type: seq<'T1>

    The first input sequence.

  • source2
    Type: seq<'T2>

    The second input sequence.





Thrown when either of the two input sequences is null.

Return Value

The predicate is applied to matching elements in the two sequences up to the lesser of the two lengths of the collections. If any application returns true then the overall result is true and no further elements are tested. Otherwise, false is returned.


If one sequence is shorter than the other then the remaining elements of the longer sequence are ignored.

This function is named Exists2 in compiled assemblies. If you are accessing the function from a language other than F#, or through reflection, use this name.


The following code example shows how to use Seq.exists2.

// Use Seq.exists2 to compare elements in two sequences.
// isEqualElement returns true if any elements at the same position in two supplied
// sequences match.
let isEqualElement seq1 seq2 = Seq.exists2 (fun elem1 elem2 -> elem1 = elem2) seq1 seq2
let seq1to5 = seq { 1 .. 5 }
let seq5to1 = seq { 5 .. -1 .. 1 }
if (isEqualElement seq1to5 seq5to1) then
    printfn "Sequences %A and %A have at least one equal element at the same position." seq1to5 seq5to1
    printfn "Sequences %A and %A do not have any equal elements that are at the same position." seq1to5 seq5to1


Sequences seq [1; 2; 3; 4; ...] and seq [5; 4; 3; 2; ...] have at least one equal element at the same position.


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


Supported in: 3

See Also


Collections.Seq Module (F#)

Microsoft.FSharp.Collections Namespace (F#)