34.2 Aycock and Horspool 2002

Marpa is based on ideas from John Aycock and R. Nigel Horspool’s “Practical Earley Parsing”, The Computer Journal, Vol. 45, No. 6, 2002, pp. 620-630. The idea of doing LR(0) precomputation for Earley’s general parsing algorithm (see Earley 1970), and Marpa’s approach to handling nullable symbols and rules, both came from this article.

The Aycock and Horspool paper summarizes Earley’s very nicely and is available on the web: http://www.cs.uvic.ca/~nigelh/Publications/PracticalEarleyParsing.pdf. Unlike Earley’s 1970 paper (see Earley 1970), Aycock and Horspool 2002 is not easy reading. I have been following this particular topic on and off for years and nonetheless found this paper very heavy going.