Enable to set dicimal digits for printing floating number

[k-okada]

dicimal digits of floating number. to recover original number from character representation, choose 17 for 64 bit machine and 9 for 32bit machine

See
https://en.m.wikipedia.org/wiki/IEEE_754#Character_representation
( https://teratail.com/questions/22355 for Japanese)

1.eusgl$ (print 1234.56789)
1234.57
1234.57
2.eusgl$ (setq lisp::*print-precision* 17)
17
3.eusgl$ (print 1234.56789) 
1234.5678899999994
1234.5678899999994

NOTE:

(print (v- #f(1234.56789) (float-vector 1234.56789)))

returns #f(0.00211) when compiled, and #f(0.0) for source because compiled files becomes

init_ftab();
��������local[0]= fqv[0];
��������local[1]= makeflt(1.2345678899999993518577e+03);
��������ctx->vsp=local+2;
��������w=(pointer)MKFLTVEC(ctx,1,local+1); /*float-vector*/
��������local[1]= w;
��������ctx->vsp=local+2;
��������w=(pointer)VMINUS(ctx,2,local+0); /*v-*/
��������local[0]= w;
��������ctx->vsp=local+1;
��������w=(pointer)PRINT(ctx,1,local+0); /*print*/

And

define QUOTE_STRINGS_SIZE 2
static char *quote_strings[QUOTE_STRINGS_SIZE]={
    "#f(1234.57)",
    "exit",
  };

FYI: @YoheiKakiuchi

[Affonso-Gui]

Is it correct to take this as a measure to print float numbers in full precision when writing to files? e.g. compiling, dump-object etc.

If it must be set to 17 in 64bit and 9 in 32bit can't we use some sort of #+/#- syntax to adapt to the running system architecture?

Having a *print-precision* variable may seem to be an alternative to (format t "~1,3f" 1234.5678) forms, which is probably not what we want.