symbol table containing symbol tables

symbol table containing symbol tables

[William W Smith]

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In pidgin OCaml I'd like to write something like

type complicated =
    IVal of int
    | StrVa, of string
    | SymTableVal of symTable
and
    symTable = Map(string -> complicated)

I tried many variations on using the Map module to implement a recursive data structure like this.  I failed miserably.  (The above wasn't the syntax I ever used, but it gets the idea across.)  

However, when I create an object
class [ 'key, 'content ] table : ('key -> 'key -> int) -> 
object
,,,
end

I can successfully declare
type complicated =
    IVal of int  
    | StrVal of string
    | SymTableVal of (string, complicated) table
that does what I want.   Ithis isn't the whole declaration of complicated, but I believe once I get this declaration working, the more quirky variations work too.

Do I need one of the more advanced features of OCaml that I don't currently understand to use Map the way that I want without writing a whole table class?  I don't even see how I can use Map from inside the table class to do what I want which would also be acceptable. 

I don't want to have to break open the Map module to modify it and thus change the licensing of my final program.

Thanks

Bill

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Re: [Caml-list] symbol table containing symbol tables

[Jon Harrop]

On Wednesday 03 January 2007 01:59, William W Smith wrote:
> Do I need one of the more advanced features of OCaml that I don't currently
> understand to use Map the way that I want without writing a whole table
> class?  I don't even see how I can use Map from inside the table class to
> do what I want which would also be acceptable.

You need recursive modules, something like this:

# module rec StringMap : Map.S = Map.Make(String)
  and Symbols : sig
    type t =
      | IVal of int
      | StrVal of string
      | SymTableVal of t StringMap.t
  end = struct
    type t =
      | IVal of int
      | StrVal of string
      | SymTableVal of t StringMap.t
  end;;
module rec StringMap : Map.S
and Symbols :
  sig
    type t = IVal of int | StrVal of string | SymTableVal of t StringMap.t
  end

HTH.

-- 
Dr Jon D Harrop, Flying Frog Consultancy Ltd.
Objective CAML for Scientists
http://www.ffconsultancy.com/products/ocaml_for_scientists

Re: [Caml-list] symbol table containing symbol tables

[Jonathan Roewen]

I don't believe you can eliminate the type variable (for the values
associated with the keys) from Map's signature. I would personally
just use a Hashtbl instead.

type complicated = Val of int | StrVal of string | SymTableVal of symTable
and symTable = (string, complicated) Hashtbl.t

Jonathan

On 1/3/07, William W Smith <sesquized@sbcglobal.net> wrote:
> In pidgin OCaml I'd like to write something like
>
> type complicated =
>     IVal of int
>     | StrVa, of string
>     | SymTableVal of symTable
> and
>     symTable = Map(string -> complicated)
>
> I tried many variations on using the Map module to implement a recursive
> data structure like this.  I failed miserably.  (The above wasn't the syntax
> I ever used, but it gets the idea across.)
>
> However, when I create an object
> class [ 'key, 'content ] table : ('key -> 'key -> int) ->
> object
> ,,,
> end
>
> I can successfully declare
> type complicated =
>     IVal of int
>     | StrVal of string
>     | SymTableVal of (string, complicated) table
> that does what I want.   Ithis isn't the whole declaration of complicated,
> but I believe once I get this declaration working, the more quirky
> variations work too.
>
> Do I need one of the more advanced features of OCaml that I don't currently
> understand to use Map the way that I want without writing a whole table
> class?  I don't even see how I can use Map from inside the table class to do
> what I want which would also be acceptable.
>
> I don't want to have to break open the Map module to modify it and thus
> change the licensing of my final program.
>
> Thanks
>
> Bill
>
> _______________________________________________
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>
>
>

Re: [Caml-list] symbol table containing symbol tables

[Jonathan Roewen]

Ooh, that's clever. An actual use case for recursive modules that's
also simple :-)

On 1/3/07, Jon Harrop <jon@ffconsultancy.com> wrote:
> On Wednesday 03 January 2007 01:59, William W Smith wrote:
> > Do I need one of the more advanced features of OCaml that I don't currently
> > understand to use Map the way that I want without writing a whole table
> > class?  I don't even see how I can use Map from inside the table class to
> > do what I want which would also be acceptable.
>
> You need recursive modules, something like this:
>
> # module rec StringMap : Map.S = Map.Make(String)
>  and Symbols : sig
>    type t =
>      | IVal of int
>      | StrVal of string
>      | SymTableVal of t StringMap.t
>  end = struct
>    type t =
>      | IVal of int
>      | StrVal of string
>      | SymTableVal of t StringMap.t
>  end;;
> module rec StringMap : Map.S
> and Symbols :
>  sig
>    type t = IVal of int | StrVal of string | SymTableVal of t StringMap.t
>  end
>
> HTH.
>
> --
> Dr Jon D Harrop, Flying Frog Consultancy Ltd.
> Objective CAML for Scientists
> http://www.ffconsultancy.com/products/ocaml_for_scientists
>
> _______________________________________________
> Caml-list mailing list. Subscription management:
> http://yquem.inria.fr/cgi-bin/mailman/listinfo/caml-list
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> Bug reports: http://caml.inria.fr/bin/caml-bugs
>