This function determines whether the provided value is a error or not.
This function does not generate a change.
is_err(value)
| Argument | Type | Description | 
|---|---|---|
| value | any (required) | The value to be tested. | 
Returns true if the given value is an error, else it returns false.
This code shows some return values for is_err():
[
    is_err( err() ),
    is_err( zero_div_err() ),
    is_err( try((1 / 0)) ),
    is_err( try((1 / 1)) ),
];
Return value in JSON format
[
    true,
    true,
    true,
    false
]