On Dec 7, 2011 10:29 AM, "Jérémie Dimino" <jeremie@dimino.org> wrote:

Hi,

I have made a patch for ocaml 3.12.1 which allow to have a generic
printing function. The patch is available here:

 http://www.dimino.org/ocaml-3.12.1-generic-print.patch

Here is how to use it:

 external show : 'a -> string = "%show"

 let () = print_endline (show ([1; 2; 3], Some "foo"))

this will print:

 ([1; 2; 3], Some "foo")

It is also possible to define custom printers, for example:

 module StringMap : sig
   include Map.S with type key = string
   val string_of_t : ('a -> string) -> 'a t -> string
 end = struct
   include Map.Make(String)
   let string_of_t (type a) string_of_a (m : a t) =
     show (bindings m)
 end

 let () = print_endline (show (StringMap.singleton "x" 1))

will print:

 [("x", 1)]

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.

The git repo is here:

 http://www.dimino.org/gitweb/?p=ocaml-3.12.1-print.git;a=summary

Cheers,

--
Jérémie



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