Adding a syntax macro facility to

iGen is a system for specifying and building programming language interpreters. iGen has been enhanced to include a macro facility that enables the underlying grammar to be extended by the programmer when the new construct can be defined in terms of existing constructs. We call this a syntax macro facility because the macros are defined via new grammar rules, which are implemented by the iGen parser. Each macro declares a new syntax rule and gives its meaning in terms of code in the programming language. iGen implements macro definitions by extending the parser to recognize the new construct. When an iGen parser encounters the new syntax it transforms the parse tree of new construct into a tree that corresponds to the semantics given in the macro.