Define

define is a keyword to define a macro. It is similar to copying and pasting: before compiling, the variable ${name} is replaced by the expression

Syntax:

define: Name = expression;

Where name is the name that we want to call the define. Expression can be anything: characters, tokens, rules.

Usage: ${Name}

Example:

define: DayPattern = ((0|1|2)?([:digit:])|3(0|1));
define: MonthPattern = ((0)?([:digit:])|1(0|1|2));
define: YearPattern = ((19|20)?([:digit:]){2});

rule : {
    <'${DayPattern}(\.|-|\/)${MonthPattern}(\.|-|\/)${YearPattern}'>
} = Date;

You can put any expression in a define, it does not need to be a string:

define: Props = (<Prop>)+ ;

rule:
{
    ${Props}
} = Propers;

"I saw John Smith

Propers -> John Smith