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Programming-Idioms

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  • Go

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.

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.
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 
return nil, fmt.Errorf("invalid value for x: %v", 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
}
error(badarg).
  if (x > largest_value) error stop "Illegal value in 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]);
die "Invalid argument $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)
    }
}