A function declares its argument list by specifying at least one argument type in a comma-separated list wrapped in parentheses following the function name. Each parameter has the following:
- A mandatory SQL type (or a user-defined type)
- An optional name
- An optional default value, which is used when the function is invoked without a value for the parameter
- An optional direction, which is used when the parameter could also be a return value
If the function does not require any arguments, the list will be empty, resulting in a couple of empty parentheses. If no name is specified for an argument, it will be available through the positional aliases $1, $2, and so on. As a simple example, consider Listing 1, where three ...
