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List.forall2<'T1,'T2> Function (F#)

  • Article

Tests if all corresponding elements of the collection satisfy the given predicate pairwise.

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

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

// Signature:
List.forall2 : ('T1 -> 'T2 -> bool) -> 'T1 list -> 'T2 list -> bool

// Usage:
List.forall2 predicate list1 list2

Parameters

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

    The function to test the input elements.

  • list1
    Type: 'T1list

    The first input list.

  • list2
    Type: 'T2list

    The second input list.

Exceptions

Exception

Condition

ArgumentException

Thrown when the input lists differ in length.

Return Value

true if all of the pairs of elements satisfy the predicate. Otherwise, returns false.

Remarks

The predicate is applied to matching elements in the two collections. If any application returns false then the overall result is false and no further elements are tested. Otherwise, if one collection is longer than the other then the ArgumentException exception is raised. Otherwise, true is returned.

This function is named ForAll2 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 code example illustrates the use of List.forall2.

let listEqual list1 list2 = List.forall2 (fun elem1 elem2 -> elem1 = elem2) list1 list2
printfn "%b" (listEqual [0; 1; 2] [0; 1; 2])
printfn "%b" (listEqual [0; 0; 0] [0; 1; 0])

Output

true
false

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

See Also

Reference

Collections.List Module (F#)

Microsoft.FSharp.Collections Namespace (F#)