"It's easy to parse scheme" is one of those pretty stories that is often repeated but untrue. A similar one is "it's easy to implement scheme in scheme". It i

"It's easy to parse scheme" is one of those pretty stories that is often repeated but untrue. A similar one is "it's easy to implement scheme in scheme". It is true for toy compilers of language subsets, and those are often done. And few people ever explore real scheme compiler internals. The readers in real scheme compilers are generally a large pile of ugly code. A decade or so ago, I recall Bigloo's was the cleanest I'd found, with a regular expression based parser framework. I can't quickly find the files to link. But after wading through many other implementations, it was a breath of fresh air. But not simple, and not small. Here's a quick quote from a Chicken changelog: "2.7 Fix several bugs (expt, integer?, rational?, <=, >=, eqv?, -) found by importing the number tests from Gauche and writing an extensive test for number syntax edge cases. Complete rewrite of number parser (it should fully conform to the R7RS superset of R5RS number syntax now)."