[Ecls-list] with-local-gmp

[Juan Jose Garcia-Ripoll]

On Saturday 07 February 2004 18:57, Erik Winkels wrote:
> Hi,
>
> It's been a while since I've done any real coding so please bear with
> my simple question: How do I use cl_write_object?

Why not use the lisp routines? cl_write_object is an internal routine,
which accidentally got the "cl_" prefix instead of the "ecl_" one (the
latter meaning: "warning! make sure you know what you're doing!")

The problem is that the lisp printer needs some auxiliary data structures
to be initialized: the pretty printter buffer, the hash of objects that
were printed in the case of *print-circle* = t, and many other values,
such as *print-base*, *print-pretty*, etc, are cached in the cl_env structure.
cl_write_object() assumes that you have properly initialized these values,
which basically amounts to calling cl_setup_printer (hey, this guy should
also have "ecl_" prefix!).

I do not like that way of working, and in a near future these auxiliary
data structures will disappear (probably a must if we want to import
CMUCL's pretty printer), so I strongly discourage you from using cl_write_object.

Instead, you have _all_ lisp functions available for C programming: cl_print,
cl_princ, cl_write, etc, and some even are in a more "compact" form which
does not check the arguments, princ, print, prin1, etc.

Finally, the lisp printer will always output to the *standard-output* stream
by default. Mixing calls to printf() and calls to the lisp printer is not
guaranteed to have the desired result. I would rather recommend using cl_format,
princ_str, princ_char, and the lisp printer, or write all lisp output to a string
and then use only the standard C writer.

A possible rewrite of your program (did not check whether it compiles)

    #include "ecl.h"
    
    #define MAX_STRING_LENGTH 80
    
    int main (int argc, char *argv[])
    {
        cl_object form, result;

        cl_boot(argc, argv);
    
        while (1)
        {
            printc_str("? ", Cnil);
	    form = cl_read(0);
            result = si_safe_eval(1, form);
            if (type_of(result) == t_string) {
		cl_format(3, Ct, make_constant_string("\"~A\"~%"), result);
            } else {
                princ_str("Output format not implemented. "
			  "Trying cl_write_object: ");
                cl_princ(1, result);
            }
        }
        
        return 0;
    }