Macros for context-free grammars

Current parser generators are based on context-free grammars. Because such grammars lack abstraction facilities, the resulting specifications are often not easy to read. Fischer's macro grammars extend context-free grammars with macro-like productions thus providing the equivalent of procedural abstraction. However, their use is hampered by the lack of an efficient, off-the-shelf parsing technology for macro grammars.