Exceptions: The failwith Function

Den Delimarsky

The failwith function generates an F# exception.


failwith error-message-string


The error-message-string in the previous syntax is a literal string or a value of type string. It becomes the Message property of the exception.

The exception that is generated by failwith is a System.Exception exception, which is a reference that has the name Failure in F# code. The following code illustrates the use of failwith to throw an exception.

let divideFailwith x y =
  if (y = 0) then failwith "Divisor cannot be zero."
    x / y

let testDivideFailwith x y =
     divideFailwith x y
     | Failure(msg) -> printfn "%s" msg; 0

let result1 = testDivideFailwith 100 0

See Also

Exception Handling

Exception Types

Exceptions: The try...with Expression

Exceptions: The try...finally Expression

Exceptions: the raise Function