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Programming-Idioms

  • Fortran
  • Go
  • Perl
  • Erlang

Idiom #89 Handle invalid argument

You've detected that the integer value of argument x passed to the current function is invalid. Write the idiomatic way to abort the function execution and signal the problem.

error(badarg).
  if (x > largest_value) error stop "Illegal value in function."

This will also stop all other images.
return nil, fmt.Errorf("invalid value for x: %v", x)

The last return parameter of the current function has type error.
It is the caller's responsibility to check if the error is nil, before using the function's other result values.
die "Invalid argument $x";
enum {
    E_OK,
    E_OUT_OF_RANGE
};

int square(int x, int *result) {
    if (x > 1073741823) {
        return E_OUT_OF_RANGE;
    }
    *result = x*x;
    return E_OK;
}
New implementation...
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programming-idioms.org 
error(badarg).
  if (x > largest_value) error stop "Illegal value in function."
return nil, fmt.Errorf("invalid value for x: %v", x)
die "Invalid argument $x";
enum {
    E_OK,
    E_OUT_OF_RANGE
};

int square(int x, int *result) {
    if (x > 1073741823) {
        return E_OUT_OF_RANGE;
    }
    *result = x*x;
    return E_OK;
}
throw domain_error("oops!");
throw new ArgumentException(nameof(×));
throw new Exception("invalid value for x (%s) in '%s'".format(x, __PRETTY_FUNCTION__));
void foo(int x)
in
{
    assert(x != 0, "wrong value for x");
}
body
{
    // function
}
throw new IllegalArgumentException("Invalid value for x: $x")
sqrt' :: Int -> Either String Int
sqrt' x | x < 0 = Left "Invalid argument"
sqrt' x         = Right (sqrt x)
throw new Error('x is invalid');
throw new IllegalArgumentException("Invalid value for x:" + x);
<T> void f(T x) {
    Objects.requireNonNull(x);
}
<T> void f(T x) throws Exception {
    if (x != value) throw new Exception();
}
void f(int x) {
    Objects.checkIndex(x, 123);
}
return nil, "Invalid argument x"
error("Invalid argument x")
throw new \InvalidArgumentException($x . ' is invalid.');
Raise EInvalidArgument.CreatFmt('Invalid value: %d',[x]);
raise ValueError("x is invalid")
raise ArgumentError, "invalid value #{x}."
enum CustomError { InvalidAnswer }

fn do_stuff(x: i32) -> Result<i32, CustomError> {
    if x != 42 {
        Err(CustomError::InvalidAnswer)
    } else {
        Ok(x)
    }
}