Re: [Caml-list] Generating a module implementation from a module signature using camlp4

[Mike McClurg <mike.mcclurg@gmail.com>]

On Fri, Oct 12, 2012 at 6:55 PM, Wojciech Meyer
<wojciech.meyer@googlemail.com> wrote:
> Hi Mike,
>
> Mike McClurg <mike.mcclurg@gmail.com> writes:
>
>> It seems that I would want to use a camlp4 filter to do this, but as
>> far as I can tell it's not possible to create a filter from sig_items
>> to str_items. Is a filter the right approach? Am I going to have to
>> define my module signatures as module type definitions from within ml
>> files? Can anyone give me some some advice on how to do this properly?
>
> You can explicitly pretty print the camlp4 quotations:
>
> open Camlp4
> open Camlp4.PreCast
> let _loc = Loc.ghost
>
> let foo nm =
>   <:str_item<module $uid:nm$ = struct let $lid:String.lowercase nm$ = () end>>
>
>
> module OCamlPrinter = Camlp4.PreCast.Printers.OCaml;;
>
> OCamlPrinter.print_implem (foo "OK")

Hi Wojciech,

Thanks for that advice. I attempted something like this earlier, but
even with your printer module I get the following:

Error: This expression has type AstFilters.Ast.str_item
       but an expression was expected of type Camlp4.PreCast.Ast.str_item

Is there any way to unify the modules AstFilters.Ast and
Camlp4.PreCast.Ast? In my earlier attempt I tried some module Foo =
Blah with module ... trickery, but I couldn't seem to unify the types
properly.

Mike