]> Dustin Sallings <dustin@spy.net> wrote: >I have a need to convert a ``string stream'' to a ``char stream.'' > Small is beautiful ! #load "camlp4o.cma";; let rec convert = parser | [< 'string; stream >] -> [<Stream.of_string string; convert stream>] | [<>] -> [<>] (* That's it... However this function compiles but doesn't work.*) (* Can anybody explain the following problem: *) let foo = [< Stream.of_string "bar"; Stream.of_string "quz">] let _ = Stream.next foo (* Exception: Failure "illegal stream concatenation". *) (* So I have to implement my own (awful : skip it!) concatenation function : *) let concat s s' = let stream_next = let rec f = ref (fun _ -> try Some (Stream.next s) with Stream.Failure -> Printf.printf "redefining f\n%!"; f := (fun _ -> (try Some (Stream.next s') with Stream.Failure -> None)); !f 0) in fun x -> !f x in Stream.from stream_next (* And then slightly rewrite my function : *) let rec convert = parser | [< 'string; stream >] -> concat (Stream.of_string string) (convert stream) | [<>] -> [<>] (*let's test it*) let foo = convert (Stream.of_list ["foo"; "bar"; ""; "qux"]) let _ = Stream.next foo;; (* - : char = 'f' *) let _ = Stream.next foo;; (* - : char = 'o' *) let _ = Stream.next foo;; (* - : char = 'o' *) let _ = Stream.next foo;; (* redefining f *) (* - : char = 'b' *) let _ = Stream.next foo;; (* - : char = 'a' *) let _ = Stream.next foo;; (* - : char = 'r' *) let _ = Stream.next foo;; (* redefining f *) (* redefining f *) (* - : char = 'q' *) let _ = Stream.next foo;; (* - : char = 'u' *) let _ = Stream.next foo;; (* - : char = 'x' *) let _ = Stream.next foo;; (* redefining f *) (* Exception: Stream.Failure. *) Except the concatenation problem, I think camlp4 makes it much clearer, and it works with empty strings. Jean-Baptiste Rouquier. ------------------- 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