Re: [Caml-list] Generic printer patch

["François Bobot" <francois.bobot@crans.org>]

Le 07/12/2011 16:28, Jérémie Dimino a écrit :
> Hi,
>
> I have made a patch for ocaml 3.12.1 which allow to have a generic
> printing function. The patch is available here:
> [...]
> Of course it is limited to what the compiler knows, for example the
> following function will always returns "[<poly>;<poly>]":
>
>    let f x = show [x; x]
>
> But i think it is already very useful for debugging.

Great job in so few time. That's right that can be an awesome feature. I 
haven't tested it yet. I just read the diff. But I have some questions :

1) If I understand well the "%show" command is expanded into the ocaml 
code (lambda-code) which can print the type. So, for instance, in the 
case of a list, your code generates a recursive function "aux" and it 
applies this new "aux" function to the argument of "%show". Do you plan 
to add in the module List a function :

val string_of_list : ('a -> string) -> 'a list -> string

and to generate only the call to this function instead of generating the 
"aux" function every time? Or do you do it purposely?

2) Could you imagine to generalize it to Format.formatter or to 
out_channel (without creating a string and concatenating)? Romain Bardou 
add in the mantis tracker (I can't give you the bugtracking number since 
mantis "is currently offline for maintenance") a feature wish for a new 
conversion specification that can print anything. Do you think you can 
fulfill is dream?

3) Is it impossible to reuse/merge with the code of the top level that 
print ocaml values?

Thank you for providing this code. Funny the way you find the user 
defined function. Be careful to not implement type classes in Ocaml ;)

-- 
François Bobot