On 12/24/2004 12:13 AM, christopher diggins wrote: [snip]
I would not say YARD is a better parser than Spirit, it is designed with quite different goals. YARD is designed to be compact and flexible. Concerning "first/follow set kind of things" I am not sure what you mean.
They're used to determine the next non-terminal to parse by looking ahead 1 terminal symbol (for LL[1] parser). Informally, they're defined for each non-terminal in the language. For a non-terminal, N, FIRST(N) is the set of non-terminals which can start a sentence derived from N. Similarly, FOLLOW(N), is the set that can follow that sentence. For a formal definition, see the paper: A Strong LL(k) Parser Generator That Accepts Non-LL Grammars and Generates LL(1) Tables: Extended Abstract available at: http://www.iit.edu/~tc/llk.htm for an implementation, see: http://cvs.sourceforge.net/viewcvs.py/boost-sandbox/boost-sandbox/boost/gram... actually, that's been replaced by one more in line with spirit (more meta-programming). I could upload it to the sandbox if you're interested.