Copyright (c) 1999 David Lichteblau <[email protected]>
This is an implementation of Meta, a technique used to simplify the task of writing parsers. Baker describes Meta and shows the main ideas for an implementation in Common Lisp:
If all META did was recognize regular expressions, it would
not be very useful. It is a programming language, however,
and the operations [], {} and $ correspond to the Common
Lisp control structures AND, OR, and DO.[8] Therefore, we
can utilize META to not only parse, but also to
transform. In this way, META is analogous to "attributed
grammars" [Aho86], but it is an order of magnitude simpler
and more efficient. Thus, with the addition of the "escape"
operation "!", which allows us to incorporate arbitrary Lisp
expressions into META, we can not only parse integers, but
produce their integral value as a result. [Baker]
The macro defined here is an attempt to implement Meta (with slightly adapted syntax) for Dylan. It is functional, but not yet optimized.