]> On Mon, Oct 06, 2003 at 09:37:40AM +0800, Rafael 'Dido' Sevilla wrote: > Now I'm stuck again. I'm revising the lexical analyzer for my compiler > to enable it to recognize escaped strings, with conventions different > from OCaml's. Currently, I'm using this regex: > > '\'' ("\\\\"|"\\'"|[^'\''])* '\'' > > in an attempt to recognize strings that begin and end with single > quotes, but may possibly include sequences like \' that represent > escaped quotes, and '\\' that represent escaped backslashes. -- As you discovered, you cannot recognize strings with a single regular expression. You need a sub-lexer: { let get = Lexing.lexeme let getchar = Lexing.lexeme_char } rule token = parse (* main lexer *) eof -> | ... | "'" -> string lexbuf (Buffer.create 80) (* use sub-lexer *) and string = parse (* lexer for strings *) eof -> { fun buf -> error "EOF in string" } | '\\' _ -> { fun buf -> let c = getchar lexbuf 1 in let k = match c with | 'n' -> '\n' | 't' -> '\t' | .... in ( Buffer.add_char buf k ; string lexbuf buf ) } | _ -> { fun buf -> string lexbuf (Buffer.add_string (get lexbuf) | "'" -> { fun buf -> Buffer.contents buf } (* return string *) -- Christian -- Christian Lindig http://www.st.cs.uni-sb.de/~lindig/ ------------------- To unsubscribe, mail caml-list-request@inria.fr Archives: http://caml.inria.fr Bug reports: http://caml.inria.fr/bin/caml-bugs FAQ: http://caml.inria.fr/FAQ/ Beginner's list: http://groups.yahoo.com/group/ocaml_beginners