14.4. How the DSL Parser Works

Whenever the DSL parser matches a line from the rule file written in the DSL with an expression in the DSL definition, it performs three steps of string manipulation:
  • The DSL extracts the string values appearing where the expression contains variable names in brackets.
  • The values obtained from these captures are interpolated wherever that name occurs on the right hand side of the mapping.
  • The interpolated string replaces whatever was matched by the entire expression in the line of the DSL rule file.

Note

You can use (for instance) a '?' to indicate that the preceding character is optional. One good reason to use this is to overcome variations in natural language phrases of your DSL. But, given that these expressions are regular expression patterns, this means that all wildcard characters in Java's pattern syntax have to be escaped with a preceding backslash ('\').
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