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String.exists Function (F#)

Tests if any character of the string satisfies the given predicate.

Namespace/Module Path: Microsoft.FSharp.Core.String

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

// Signature:
String.exists : (char -> bool) -> string -> bool

// Usage:
String.exists predicate str


Type: char -> bool

The function to test each character of the string.


Type: string

The input string.




Thrown when the input string is null.

Returns true if any character returns true for the predicate and false otherwise.

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

The following code shows how to use String.exists.

let containsUppercase string1 =
    if (String.exists (fun c -> System.Char.IsUpper(c)) string1) then
        printfn "The string \"%s\" contains uppercase characters." string1
        printfn "The string \"%s\" does not contain uppercase characters." string1
containsUppercase "Hello World!"
containsUppercase "no"


The string "Hello World!" contains uppercase characters.
The string "no" does not contain uppercase characters.

Windows 8, Windows 7, Windows Server 2012, Windows Server 2008 R2

F# Core Library Versions

Supported in: 2.0, 4.0, Portable

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