Regexp matching on character streams. The main idea is to provide a simple regular expressions library which takes characters not from string but from function "get":

val get: unit -> char Lwt.t

Primitives supported: "c" Matches character "c" "[abc]" Matches any of listed characters "[^abc]" Matches any of NOT listed characters "[\^\]]" Matches "^" or "]" "[^\^\]]" Matches NOT "^" and NOT "]" "(grp)" Grouping. Matched group can be extracted from result using function "nth". "." Matches any character. Be careful, Rex regexps have no looking-forward algorithms. Regexps such as ".+a" will not ever stop.

Repetition primitives: "c" Matches exactly one character "c" "c?" Matches zero or one "c" "c*" Matches zero or more of "c"'s "c+" Matches one or more of "c"'s "c{2,5}" Matches 2..5 of "c"'s

Usage example:

let regexp = Rex.regexp "GET ([^ ]+) HTTP"

let get = let s = "GET /some/uri HTTP/1.1\n" in let pos = ref 0 in fun () -> let r = s.[pos] in incr pos; Lwt.return r

let match = lwt r = Rex.apply ~get regexp in let result = match r with | None -> "no match" | Some r -> let uri = Rex.nth r 0 in "URI=" ^ uri in Printf.printf "result is: %s\n" result

let _ = Lwt_unix.run match