Re: [Caml-list] a generic print (ugly hack)

["Nicolas Cannasse" <warplayer@free.fr>]

> the goal is to allow the programmer to write in his program for instance:
>
>  let _ = print_string (generic_print [[1;3];[2;9;8];[3;4]] "int list
list") in
>  ...
>  let _ = print_string (generic_print [1;3;2;9;8;3;4] "int list") in
>  let v = ... (* big computation, big data structure *)
>  let _ = print_string (generic_print v "(int * float * color) assoc") in
>  ...
>
>
> and to get on stdout:
>  [[1; 3]; [2; 9; 8]; [3; 4]]
>  [1; 3; 2; 9; 8; 3; 4]
>  [(1, 2.02, Red); (2, 4.02, Yellow)];
>
>
> the type of generic_print is
>  'a -> string -> string
>
> code:
>  http://www.irisa.fr/prive/padiolea/hacks/generic_print.ml
>
> the principle is that the toplevel of O'Caml know how to print value,
> so by "reusing" the toplevel, our program can too.
>
>
> It is slow, ugly, not robust,  but it can be helpful.
> any suggestion or critics are welcome.

I was thinking doing the same some times ago, but without relying on
toplevel (which stucks you to bytecode).
The idea was to be able to load CMI at runtime, and extract type
informations from it in order to correctly print and match types (this is
already what's doing ODLL with functions). It's quite a work and I didn't
finished it. CMI contains *exact* types informations which are not present
at runtime, but not structured in a convenient way for printing or matching
since they're directly dumped from the compiler type representation. But
once done, this would include some dynamism that ocaml lacks when
interacting with outter world (serialization for example).

Nicolas Cannasse

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