The primary resource for all things to do with parsing expressions can be found on the original Packrat and Parsing Expression Grammars page at MIT.
Also, a useful summary of parsing expression grammars can be found on Wikipedia.
Citrus draws inspiration from another Ruby library for writing parsing expression grammars, Treetop. While Citrus' syntax is similar to that of Treetop, it’s not identical. The link is included here for those who may wish to explore an alternative implementation.
Copyright © 2015 Michael Jackson