Toplevel function question

Toplevel function question

[Joel Christner]

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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
File "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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Re: Toplevel function question

[Joel Christner]

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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
File "toplevel.ml", line 17, characters 1-1:
Syntax error




On Wed, May 13, 2009 at 4:43 PM, Joel Christner <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
> File "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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RE : [Caml-list] Re: Toplevel function question

[MONATE Benjamin 205998]

Hi,

The last "let" is missing its corresponding "in".
 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
  in parsepreogram

You may also remove the last "let": 

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 
  List.iter
    (fun n -> print_string n; print_string "\n";) originalprogramcontents

Hope this helps.
--
Benjamin Monate
CEA LIST
Head of Software Safety Lab.

Re: [Caml-list] Re: Toplevel function question

[Gregory BELLIER]

Hello !

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
>

Please refer to the last email from John Li.
variablelist := test :: !variablelist


> 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
Here you should call _*!*_originalprogramcontents which seems to be 
empty with your example because you declare the function 
storeoriginalprogram but you don't use/call it.

Try something like :

let myvariable = 1 in

let rec fun var =
       match var with
    | val1 -> ...
    | val2 -> ...
    | _ -> ...
in
    fun my_variable   ( <<--- this is what you forgot )

Gregory.

Re: [Caml-list] Re: Toplevel function question

[Cedric Auger]

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
>
>
> ------------------------------------------------------------------------
>
> _______________________________________________
> Caml-list mailing list. Subscription management:
> http://yquem.inria.fr/cgi-bin/mailman/listinfo/caml-list
> Archives: http://caml.inria.fr
> Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
> Bug reports: http://caml.inria.fr/bin/caml-bugs
>   


-- 
Cédric AUGER

Univ Paris-Sud, Laboratoire LRI, UMR 8623, F-91405, Orsay

Re: [Caml-list] Re: Toplevel function question

[Cedric Auger]

And one last thing in your title, avoid using "toplevel" term as it 
often refers to the program runned by typing "ocaml", that is the 
interactive system, so it is a bit confusing.

Cedric Auger a écrit :
> 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
>>
>>
>> ------------------------------------------------------------------------
>>
>> _______________________________________________
>> Caml-list mailing list. Subscription management:
>> http://yquem.inria.fr/cgi-bin/mailman/listinfo/caml-list
>> Archives: http://caml.inria.fr
>> Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
>> Bug reports: http://caml.inria.fr/bin/caml-bugs
>>   
>
>


-- 
Cédric AUGER

Univ Paris-Sud, Laboratoire LRI, UMR 8623, F-91405, Orsay