[Python-checkins] CVS: python/dist/src/Objects floatobject.c,2.52,2.53

[Guido van Rossum]

Update of /projects/cvsroot/python/dist/src/Objects
In directory eric:/projects/python/develop/guido/src/Objects

Modified Files:
	floatobject.c 
Log Message:
Implement the other easy thing: repr() of a float now uses %.17g,
while str() uses %.12g as before.


Index: floatobject.c
===================================================================
RCS file: /projects/cvsroot/python/dist/src/Objects/floatobject.c,v
retrieving revision 2.52
retrieving revision 2.53
diff -C2 -r2.52 -r2.53
*** floatobject.c	1999/10/12 19:54:48	2.52
--- floatobject.c	1999/12/23 19:00:28	2.53
***************
*** 244,250 ****
  
  void
! PyFloat_AsString(buf, v)
  	char *buf;
  	PyFloatObject *v;
  {
  	register char *cp;
--- 244,251 ----
  
  void
! PyFloat_AsStringEx(buf, v, precision)
  	char *buf;
  	PyFloatObject *v;
+ 	int precision;
  {
  	register char *cp;
***************
*** 254,258 ****
  	   However, %g may print the number as an integer;
  	   in such cases, we append ".0" to the string. */
! 	sprintf(buf, "%.12g", v->ob_fval);
  	cp = buf;
  	if (*cp == '-')
--- 255,259 ----
  	   However, %g may print the number as an integer;
  	   in such cases, we append ".0" to the string. */
! 	sprintf(buf, "%.*g", precision, v->ob_fval);
  	cp = buf;
  	if (*cp == '-')
***************
*** 271,274 ****
--- 272,300 ----
  }
  
+ /* Precisions used by repr() and str(), respectively.
+ 
+    The repr() precision (17 significant decimal digits) is the minimal number
+    that is guaranteed to have enough precision so that if the number is read
+    back in the exact same binary value is recreated.  This is true for IEEE
+    floating point by design, and also happens to work for all other modern
+    hardware.
+ 
+    The str() precision is chosen so that in most cases, the rounding noise
+    created by various operations is suppressed, while giving plenty of
+    precision for practical use.
+ 
+ */
+ 
+ #define PREC_REPR	17
+ #define PREC_STR	12
+ 
+ void
+ PyFloat_AsString(buf, v)
+ 	char *buf;
+ 	PyFloatObject *v;
+ {
+ 	PyFloat_AsStringEx(buf, v, PREC_STR);
+ }
+ 
  /* ARGSUSED */
  static int
***************
*** 279,283 ****
  {
  	char buf[100];
! 	PyFloat_AsString(buf, v);
  	fputs(buf, fp);
  	return 0;
--- 305,309 ----
  {
  	char buf[100];
! 	PyFloat_AsStringEx(buf, v, flags&Py_PRINT_RAW ? PREC_STR : PREC_REPR);
  	fputs(buf, fp);
  	return 0;
***************
*** 288,293 ****
  	PyFloatObject *v;
  {
  	char buf[100];
! 	PyFloat_AsString(buf, v);
  	return PyString_FromString(buf);
  }
--- 314,328 ----
  	PyFloatObject *v;
  {
+ 	char buf[100];
+ 	PyFloat_AsStringEx(buf, v, PREC_REPR);
+ 	return PyString_FromString(buf);
+ }
+ 
+ static PyObject *
+ float_str(v)
+ 	PyFloatObject *v;
+ {
  	char buf[100];
! 	PyFloat_AsStringEx(buf, v, PREC_STR);
  	return PyString_FromString(buf);
  }
***************
*** 674,682 ****
  	0,			/*tp_setattr*/
  	(cmpfunc)float_compare, /*tp_compare*/
! 	(reprfunc)float_repr, /*tp_repr*/
  	&float_as_number,	/*tp_as_number*/
  	0,			/*tp_as_sequence*/
  	0,			/*tp_as_mapping*/
! 	(hashfunc)float_hash, /*tp_hash*/
  };
  
--- 709,719 ----
  	0,			/*tp_setattr*/
  	(cmpfunc)float_compare, /*tp_compare*/
! 	(reprfunc)float_repr,	/*tp_repr*/
  	&float_as_number,	/*tp_as_number*/
  	0,			/*tp_as_sequence*/
  	0,			/*tp_as_mapping*/
! 	(hashfunc)float_hash,	/*tp_hash*/
!         0,			/*tp_call*/
!         (reprfunc)float_str,	/*tp_str*/
  };