Re: Suggested fix in numbers.c

[Roland Orre <orre@nada.kth.se>]

On tor, 2003-01-16 at 02:43, Thien-Thi Nguyen wrote:
>    From: Roland Orre <orre@nada.kth.se>
>    Date: 29 Dec 2002 00:25:58 +0100
> 
>    Below is my standard fix to numbers.c [...]
> 
> thanks for this; i've installed it in 1.4.1.x cvs.  the changes were
> small enough that no papers are required.  i would like to mention this
> feature in the documentation; could you provide a suitable example?

I include here example code using a C format string for float values.

This is useful when for instance dealing with float
vectors. Assume that we make the following input:
> (define foo #s(1.1 1.3 1.7))
The foo vector will be by default be displayed as:
> foo
#s(1.10000002384186 1.29999995231628 1.70000004768372)
Now e.g. define float format to be the C-string "%g"
> (float-format "%g")
> foo
#s(1.1 1.3 1.7)

The user code below is an example of an implementation of
USER_FLOAT_FORMAT. In your setup do #define USER_FLOAT_FORMAT 1
then the following code will allow you to set float format to a C
format string:

size_t scm_idbl2str(double f, char *a);
extern size_t (*scm_user_idbl2str)(double f,char *a);
static char float_format_string[40];
static size_t user_idbl2str(double f,char *a)
{ 
  return (size_t)sprintf(a,float_format_string,f);
} /* user_idbl2str */

SCM_PROC(s_float_format,"float-format",0,1,0,float_format);
/* returns #f if default format is used otherwise returns format string.
   Optional format may be #f or format string. */
SCM float_format(SCM format)
{
  SCM res;
  if SCM_UNBNDP(format) {
    if (scm_user_idbl2str==scm_idbl2str) /* default float conversion */
      return SCM_BOOL_F;
    else {
      res=scm_makstr(strlen(float_format_string),0);
      strcpy(SCM_CHARS(res),float_format_string);
      return res;
    }
  }
  if (SCM_FALSEP(format)) {
    scm_user_idbl2str=scm_idbl2str;	 /* default float conversion */
    return SCM_BOOL_F;
  }
 
SCM_ASSERT(SCM_NIMP(format)&&SCM_STRINGP(format),format,SCM_ARG1,s_float_format);
  strcpy(float_format_string,SCM_CHARS(format));
  scm_user_idbl2str=user_idbl2str;	/* user float conversion */
  return SCM_BOOL_T;
} /* float_format */

On tor, 2003-01-16 at 02:43, Thien-Thi Nguyen wrote:
>    From: Roland Orre <orre@nada.kth.se>
>    Date: 29 Dec 2002 00:25:58 +0100
> 
>    Below is my standard fix to numbers.c [...]
> 
> thanks for this; i've installed it in 1.4.1.x cvs.  the changes were
> small enough that no papers are required.  i would like to mention this
> feature in the documentation; could you provide a suitable example?
> 
> thi



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