[Caml-list] Doubt about function delaration parameter

[Caml-list] Doubt about function delaration parameter

[sieira]

Why doesn't this work?:

type menu = {Textos: string list; Claves:string list};;

let menu_principal = {Textos = ["Clientes";"Operaciones"];Claves =
["1";"2"]};;
let rec pinta_menu = function
      {Textos = []; Claves = []} ->
	  begin
	    print_string ">";
	    ();
	  end
      | {Textos = _; Claves = []} -> 
	  begin
	    print_string "[EE] Error en el menu";
	    ();
	  end
      | {Textos = []; Claves = _} -> 
	  begin
	    print_string "[EE] Error en el menu";
	    ();
	    end
      | {Textos = texto::textos; Claves = clave::claves} -> 
	begin
	  print_string texto^"Una dola\n";
	  pinta_menu({Textos = textos; Claves = claves});
	end;;


(Returns 

"This expression has type unit"
)

While this does:

let rec pinta_menu = function
      [],[] ->
	  begin
	    print_string ">";
	    ();
	  end
      |  _,[] -> 
	  begin
	    print_string "[EE] Error en el menu";
	    ();
	  end
      | [];_} -> 
	  begin
	    print_string "[EE] Error en el menu";
	    ();
	    end
      | texto::textos;clave::claves -> 
	begin
	  print_string texto^"Una dola\n";
	  pinta_menu({Textos = textos; Claves = claves});
	end;;

	pinta_menu(menu_principal);;


Note that Textos ean texts and Claves mean keys


	pinta_menu(menu_principal);;
-- 
View this message in context: http://old.nabble.com/Doubt-about-function-delaration-parameter-tp30464033p30464033.html
Sent from the Caml Discuss mailing list archive at Nabble.com.

Re: [Caml-list] Doubt about function delaration parameter

[Ashish Agarwal]

[-- Attachment #1: Type: text/plain, Size: 2439 bytes --]

Record field names must start with a lower case letter, so I cannot
reproduce the error you mention.

Also note you can simplify code like:

    print_string "foo"; ();

to simply

    print_string "foo"

Since print_string "foo" already returns unit, it is unnecessary to
explicitly return unit after this.


On Wed, Dec 15, 2010 at 9:03 AM, sieira <jaimito.hendrix@gmail.com> wrote:

>
> Why doesn't this work?:
>
> type menu = {Textos: string list; Claves:string list};;
>
> let menu_principal = {Textos = ["Clientes";"Operaciones"];Claves =
> ["1";"2"]};;
> let rec pinta_menu = function
>      {Textos = []; Claves = []} ->
>          begin
>            print_string ">";
>            ();
>          end
>      | {Textos = _; Claves = []} ->
>          begin
>            print_string "[EE] Error en el menu";
>            ();
>          end
>      | {Textos = []; Claves = _} ->
>          begin
>            print_string "[EE] Error en el menu";
>            ();
>            end
>      | {Textos = texto::textos; Claves = clave::claves} ->
>        begin
>          print_string texto^"Una dola\n";
>          pinta_menu({Textos = textos; Claves = claves});
>        end;;
>
>
> (Returns
>
> "This expression has type unit"
> )
>
> While this does:
>
> let rec pinta_menu = function
>      [],[] ->
>          begin
>            print_string ">";
>            ();
>          end
>      |  _,[] ->
>          begin
>            print_string "[EE] Error en el menu";
>            ();
>          end
>      | [];_} ->
>          begin
>            print_string "[EE] Error en el menu";
>            ();
>            end
>      | texto::textos;clave::claves ->
>        begin
>          print_string texto^"Una dola\n";
>          pinta_menu({Textos = textos; Claves = claves});
>        end;;
>
>        pinta_menu(menu_principal);;
>
>
> Note that Textos ean texts and Claves mean keys
>
>
>        pinta_menu(menu_principal);;
> --
> View this message in context:
> http://old.nabble.com/Doubt-about-function-delaration-parameter-tp30464033p30464033.html
> Sent from the Caml Discuss mailing list archive at Nabble.com.
>
> _______________________________________________
> 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
>

[-- Attachment #2: Type: text/html, Size: 3710 bytes --]

Re: [Caml-list] Doubt about function delaration parameter

[Esther Baruk]

[-- Attachment #1: Type: text/plain, Size: 2318 bytes --]

When you write :

 print_string texto^"Una dola\n";

you must put parenthesis around your string : print_string (texto^"Una
dola\n");

Otherwise it means you concatenates a string with a thing of type unit.


Esther


2010/12/15 sieira <jaimito.hendrix@gmail.com>

>
> Why doesn't this work?:
>
> type menu = {Textos: string list; Claves:string list};;
>
> let menu_principal = {Textos = ["Clientes";"Operaciones"];Claves =
> ["1";"2"]};;
> let rec pinta_menu = function
>      {Textos = []; Claves = []} ->
>          begin
>            print_string ">";
>            ();
>          end
>      | {Textos = _; Claves = []} ->
>          begin
>            print_string "[EE] Error en el menu";
>            ();
>          end
>      | {Textos = []; Claves = _} ->
>          begin
>            print_string "[EE] Error en el menu";
>            ();
>            end
>      | {Textos = texto::textos; Claves = clave::claves} ->
>        begin
>          print_string texto^"Una dola\n";
>          pinta_menu({Textos = textos; Claves = claves});
>        end;;
>
>
> (Returns
>
> "This expression has type unit"
> )
>
> While this does:
>
> let rec pinta_menu = function
>      [],[] ->
>          begin
>            print_string ">";
>            ();
>          end
>      |  _,[] ->
>          begin
>            print_string "[EE] Error en el menu";
>            ();
>          end
>      | [];_} ->
>          begin
>            print_string "[EE] Error en el menu";
>            ();
>            end
>      | texto::textos;clave::claves ->
>        begin
>          print_string texto^"Una dola\n";
>          pinta_menu({Textos = textos; Claves = claves});
>        end;;
>
>        pinta_menu(menu_principal);;
>
>
> Note that Textos ean texts and Claves mean keys
>
>
>        pinta_menu(menu_principal);;
> --
> View this message in context:
> http://old.nabble.com/Doubt-about-function-delaration-parameter-tp30464033p30464033.html
> Sent from the Caml Discuss mailing list archive at Nabble.com.
>
> _______________________________________________
> 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
>

[-- Attachment #2: Type: text/html, Size: 4951 bytes --]

Re: [Caml-list] Doubt about function delaration parameter

[sieira]

Thanks for your replies. I'm now having some issue with Raphael's suggestion
of using (string * string) list;; as the menu type.


type menu = (string*string) list;;

Results in a syntax error at the first parenthesis, while

type menu = string*string;;

fails too (at the asterisk)

It seems like I'm missing something. Since according to the 
http://caml.inria.fr/pub/docs/manual-caml-light/node3.5.html documentantion
, this sintax should be right.

I'm using Camllight 0.81 by François Boisson running in Ubuntu lucid lynx


-- 
View this message in context: http://old.nabble.com/Doubt-about-function-delaration-parameter-tp30464033p30465308.html
Sent from the Caml Discuss mailing list archive at Nabble.com.

RE: [Caml-list] Doubt about function delaration parameter

[David Allsopp]

sieira wrote:
> Thanks for your replies. I'm now having some issue with Raphael's
> suggestion of using (string * string) list;; as the menu type.
> 
> 
> type menu = (string*string) list;;
> 
> Results in a syntax error at the first parenthesis, while
> 
> type menu = string*string;;
> 
> fails too (at the asterisk)
> 
> It seems like I'm missing something. Since according to the
> http://caml.inria.fr/pub/docs/manual-caml-light/node3.5.html
> documentantion , this sintax should be right.
> 
> I'm using Camllight 0.81 by François Boisson running in Ubuntu lucid lynx

People on this list will reasonably assume you're using Objective Caml unless you say otherwise - this should have been at the top of your original post. I don't know and don't have access to an installation of caml light but looking at http://caml.inria.fr/pub/docs/manual-caml-light/node3.9.html it would appear to me as though type abbreviations (which is what you're doing) need == in Caml Light:

type menu == (string*string) list;;

... but I may well be wrong.


David

Re: [Caml-list] Doubt about function delaration parameter

[Raphael Proust]

Le mercredi 15 décembre 2010 17:15:23, sieira a écrit :
> Thanks for your replies. I'm now having some issue with Raphael's
> suggestion of using (string * string) list;; as the menu type.
> 
> 
> type menu = (string*string) list;;
> 
> Results in a syntax error at the first parenthesis, while
> 
> type menu = string*string;;
> 
> fails too (at the asterisk)
> 
> It seems like I'm missing something. Since according to the
> http://caml.inria.fr/pub/docs/manual-caml-light/node3.5.html documentantion
> , this sintax should be right.
> 
> I'm using Camllight 0.81 by François Boisson running in Ubuntu lucid lynx

I just installed Camllight and I encountered the problem as you. Because the 
type menu is just a shorter name for the complete type (string * string) list, 
you have to use:
type menu == ( string * string ) list ;;

(with two '=' signs)
I don't know the exact rule about this. It might be close to the difference 
between 'type' and 'data' in Haskell.

Good luck!
-- 
_______
Raphaël

Re: [Caml-list] Doubt about function delaration parameter

[bluestorm]

[-- Attachment #1: Type: text/plain, Size: 3133 bytes --]

In Caml Light, the rule is the following :
- if you declare a *new* type, such as a sum type ( Foo | Bar | Baz ) or a
record type ( { foo : t; bar : t' } ), use "="
- if you just add an alias, a new name for an existing type, use "=="

It is an alias if the right-hand side is a "type expression" (something you
could use as is in a type annotation)

It is interesting to note that, though less syntactically visible, the
difference has not vanished in OCaml.
OCaml type declarations may have two components, a type "equation" (~ alias
for a type expression) and a "representation" (~ new ADT). For example the
following is valid :

  type test = A.ty = A | B | C

The type is declared to be an alias to the type "ty" in the module A, and
also represented by the sum (A | B | C) : the definition is "re-exported",
and an error will be thrown if A.ty is different from (A | B | C). It is
occasionnaly nice to make representation explicit, while still keeping
compatibility at the type level (the two types are considered equal by the
type checker), and can also be avoid to "strenghten" an external dependency
: if the upstream type definition changes, I'm sure my code will fail here
instead of producing weird errors later.
See the OCaml manual :
http://caml.inria.fr/pub/docs/manual-ocaml/manual016.html

The difference between type declarations and alias/abbreviation is also
significant for the semantics of "private types", which are an extension (or
rather several successive extensions) to the OCaml language described here
: http://caml.inria.fr/pub/docs/manual-ocaml/manual021.html#toc76 .



On Wed, Dec 15, 2010 at 5:56 PM, Raphael Proust <raphlalou@gmail.com> wrote:

> Le mercredi 15 décembre 2010 17:15:23, sieira a écrit :
> > Thanks for your replies. I'm now having some issue with Raphael's
> > suggestion of using (string * string) list;; as the menu type.
> >
> >
> > type menu = (string*string) list;;
> >
> > Results in a syntax error at the first parenthesis, while
> >
> > type menu = string*string;;
> >
> > fails too (at the asterisk)
> >
> > It seems like I'm missing something. Since according to the
> > http://caml.inria.fr/pub/docs/manual-caml-light/node3.5.html
>  documentantion
> > , this sintax should be right.
> >
> > I'm using Camllight 0.81 by François Boisson running in Ubuntu lucid lynx
>
> I just installed Camllight and I encountered the problem as you. Because
> the
> type menu is just a shorter name for the complete type (string * string)
> list,
> you have to use:
> type menu == ( string * string ) list ;;
>
> (with two '=' signs)
> I don't know the exact rule about this. It might be close to the difference
> between 'type' and 'data' in Haskell.
>
> Good luck!
> --
> _______
> Raphaël
>
> _______________________________________________
> 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
>
>

[-- Attachment #2: Type: text/html, Size: 4617 bytes --]