You should use these macros to get access to the command parameters. Usually these parameters are presented as "nodes". Syntax definition usually allows you to use expressions whenever a long, double or string is expected. Expressions are converted to "nodes" and therefore only a few commands may use the macros PARAMETERLONG, PARAMETERDOUBLE or PARAMETERSTRING. These can be used when the parameter is a long number, double number or a contant string and NOT an expression or expression list.
When a command has more than one parameters you can access each, step by step using the macro NEXTPARAMETER, which steps onto the next parameter of the command.
Do NOT use any of the PARAMETERXXX macro or the macro NEXTPARAMETER in the implementation of a built-in function.