[kristianp]

Informative comment, but surely the purpose of the article is to teach ocaml, not the lexing&parsing tools, which require more ocaml knowledge?

[toolslive]

The author doesn't appear to be an experienced OCaml programmer, and misses lots of opportunities for simpler code. For example

let is_digit c = let code = Char.code c in code >= Char.code('0') && code <= Char.code('9')

Could have been written: let is_digit = function '0'..'9' -> true | _ -> false

So the purpose probably wasn't to teach OCaml.