The article is divided into three stages: simple top-down parser
combinators, continuation-passing style, and trampolined dispatch.
These correspond to 1/parser.rkt, 2/parser.rkt and 3/parser.rkt.
Make the third version of the code consistent with the article's
sections "Trampoline" and "Final improvements".
Make the second version of the code consistent with the article's
section "Continuation-passing style".
Simple parser combinators
Make the first version of the code consistent with the article's
sections "Simple parser combinators" and "Memoization".
The code is licensed under the MIT License.