Defines a macro with only one argument, where that argument can include commas.
This macro preprocessor directive defines a macro with only one argument, where that argument can have commas in it. #def1arg is a special version of #define, since #define treats commas within arguments as delimiters between arguments. It has the form:
#def1arg Macro(%Arg) Value
Macro is the name of the macro being defined, which accepts only one argument. A valid macro name is an alphanumeric string.
%Arg is the name of the argument for the macro. The name of the variable specifying the macro’s argument must begin with a percent sign.
Value is the macro’s value, which includes the use of value of %Arg specified at runtime
A #def1arg line can include a ##; comment.
For more information on defining macros generally, see the entry for #define.
For example, the following MarxBros macro accepts the comma-separated list of the names of the Marx brothers as its argument:
#def1arg MarxBros(%MBNames) WRITE "%MBNames:",!,"The Marx Brothers!",!
// some movies have all four of them
$$$MarxBros(Groucho, Chico, Harpo, and Zeppo)
// some movies only have three of them
$$$MarxBros(Groucho, Chico, and Harpo)
where the MarxBros macro takes an argument, %MBNames argument, which accepts a comma-delimited list of the names of the Marx brothers.