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Toplevel function question
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| Date: | -- (:) |
| From: | Cedric Auger <Cedric.Auger@l...> |
| Subject: | Re: [Caml-list] Re: Toplevel function question |
Joel Christner a écrit :
> Simpler representation - tried compiling this and got the same syntax
> error - at a line number that was after the EOF. Thanks in advance
> for any help!!
>
> let add_text variablelist text =
> variablelist.contents <- text::variablelist.contents
>
> let originalprogramcontents = ref [""]
>
> let _ =
> let lexbuf = Lexing.from_channel stdin in
> let rec storeoriginalprogram =
> let expr = lexbuf in
> match expr with
> | EOF -> ()
> | _ -> (add_text originalprogramcontents expr);
> storeoriginalprogram
> in let parseprogram = List.iter
> (fun n -> print_string n; print_string "\n";) originalprogramcontents
>
> $ ocamlc -c toplevel.ml <http://toplevel.ml>
> File "toplevel.ml <http://toplevel.ml>", line 17, characters 1-1:
> Syntax error
>
Why do you use ( and ) delimiting "add_text originalprogramcontents expr"?
in (fun n -> print_string n; print_string "\n";), last ";" is useless
as Benjamin said your "let" is missing its "in"
eventually I assume you didn't intended to write "expr = lexbuf", but
rather "expr = parse lexbuf", where parse is a function you must define,
probably the "Parser.expr Scanner.token" of your first mail, so I think
that the following would be better:
let add_text variablelist text =
variablelist := text::!variablelist
let originalprogramcontents = ref [""]
let _ =
let lexbuf = Lexing.from_channel stdin in
let rec storeoriginalprogram =
let expr = Parser.expr Scanner.token lexbuf in
match expr with
| EOF -> ()
| _ -> add_text originalprogramcontents expr; storeoriginalprogram
in
List.iter
(fun n -> print_string n; print_string "\n")
originalprogramcontents
And I don't think "let _ =" is mandatory
Note that a list can be empty and you can write
let originalprogramcontents = ref []
if you want an empty list at beginning (I don't know if you need an
empty list or a list containing an empty string), caml will guess its
type since you used add_text on this list.
If you don't use the list or want to restrict a type you also can "cast" it:
let (originalprogramcontents : (string list) ref) = ref []
>
>
>
> On Wed, May 13, 2009 at 4:43 PM, Joel Christner
> <joel.christner@gmail.com <mailto:joel.christner@gmail.com>> wrote:
>
> Hello,
>
> I hope you guys don't mind another beginner's question, I'm
> waiting on approval from the Yahoo! group moderator for the
> beginner's section.
>
> I'm trying to implement a toplevel function that will accept input
> from stdin (someone running the program will do ./programname <
> someinputfile), store it to a ref string list, and then once
> stored, iteratively evaluate each item in the list individually.
>
> What I've put together is:
>
> let _ =
> let lexbuf = Lexing.from_channel stdin in
> let rec storeoriginalprogram =
> let expr = Parser.expr Scanner.token lexbuf in
> match expr with
> | EOF -> ()
> | _ -> add_text originalprogramcontents expr;
> storeoriginalprogram
> in let parseprogram = List.iter
> (fun n -> eval expr) originalprogramcontents
>
> where...
> - Parser and Scanner are already built and working great
> - When a line of text comes in, it calls 'add_text' which adds the
> expr into the 'originalprogramcontents' ref string list, and then
> recursively calls itself to get the next line
> - let originalprogramcontents = ref [""]
> - let add_text variablelist text = variablelist.contents <-
> text::variablelist.contents
> - Then when finished reading from stdin, iteratively executes
> 'eval' against each line in the ref string list called
> 'originalprogramcontents'
>
> For some reason (probably a stupid mistake on my part) it's giving
> me a syntax error and pointing to a line of code that is AFTER the
> end of my program:
>
> $ make
> ocamlc -c program.ml <http://program.ml>
> File "program.ml <http://program.ml>", line 203, characters 2-2:
> Syntax error
> make: *** [program.cmo] Error 2
>
> But my program is only 202 lines long.
>
> Any ideas on how I might go about making this work?
>
> Thanks
> Joel
>
>
> ------------------------------------------------------------------------
>
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--
Cédric AUGER
Univ Paris-Sud, Laboratoire LRI, UMR 8623, F-91405, Orsay