$0.02 suggestion for the Printf module

$0.02 suggestion for the Printf module

[Alain Frisch]

As I didn't find a powerful enough preprocessor, and I find perl ugly,
I try to use OCaml to generate text file (html, latex, etc ...).

So I have a global mutable variable containing a printing function.
In different situation, this function write directly to a file or add the
text to a buffer (to preprocess it before sending it), or filter the text
through another function, etc ...

I want to use the printf formating functions. With the current Printf
module, I have to use create a buffer, bprintf in the buffer, extract the
content of the buffer, print this string with my printing function.

As I want to do it often, it would be useful to have a function :

gen_printf: (string -> ()) -> ('a, Buffer.t, unit) format -> 'a
[or for performance (string -> ()) -> (char -> ()) -> ('a, ... ]

taking as its first argument a 'printing function'

(so printf == gen_printf print_string; etc ...)

As far as I know it is impossible to implement it in the core langage,   
so the only solution for the moment is to hack with the source code of   
Printf (it takes 20 seconds to implement gen_printf from printf).

I think it would be a good idea to add such a function in the Printf 
module.


Btw, I don't understand the tests performed on the format 'string' in
Printf functions : aren't they already done by the compiler during the
typing ?


--
Alain Frisch

$0.02 suggestion for the Printf module

[William Chesters]

Alain Frisch writes:
 > As I want to do it often, it would be useful to have a function :
 > 
 > gen_printf: (string -> ()) -> ('a, Buffer.t, unit) format -> 'a
 > [or for performance (string -> ()) -> (char -> ()) -> ('a, ... ]
 > 
 > taking as its first argument a 'printing function'

You can do this with Format (and of course you get pretty-printing as
well)---see Format.formatter_of_out_channel, etc.  I don't know what
the performance difference, if any, between Printf and Format is.