diff options
Diffstat (limited to 'Objects/floatobject.c')
| -rw-r--r-- | Objects/floatobject.c | 49 |
1 files changed, 43 insertions, 6 deletions
diff --git a/Objects/floatobject.c b/Objects/floatobject.c index cb5d9e3..557a641 100644 --- a/Objects/floatobject.c +++ b/Objects/floatobject.c @@ -243,9 +243,10 @@ PyFloat_AsDouble(op) /* Methods */ void -PyFloat_AsString(buf, v) +PyFloat_AsStringEx(buf, v, precision) char *buf; PyFloatObject *v; + int precision; { register char *cp; /* Subroutine for float_repr and float_print. @@ -253,7 +254,7 @@ PyFloat_AsString(buf, v) i.e., they should contain a decimal point or an exponent. However, %g may print the number as an integer; in such cases, we append ".0" to the string. */ - sprintf(buf, "%.12g", v->ob_fval); + sprintf(buf, "%.*g", precision, v->ob_fval); cp = buf; if (*cp == '-') cp++; @@ -270,6 +271,31 @@ PyFloat_AsString(buf, v) } } +/* 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 float_print(v, fp, flags) @@ -278,7 +304,7 @@ float_print(v, fp, flags) int flags; /* Not used but required by interface */ { char buf[100]; - PyFloat_AsString(buf, v); + PyFloat_AsStringEx(buf, v, flags&Py_PRINT_RAW ? PREC_STR : PREC_REPR); fputs(buf, fp); return 0; } @@ -288,7 +314,16 @@ float_repr(v) PyFloatObject *v; { char buf[100]; - PyFloat_AsString(buf, v); + 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); } @@ -673,11 +708,13 @@ PyTypeObject PyFloat_Type = { 0, /*tp_getattr*/ 0, /*tp_setattr*/ (cmpfunc)float_compare, /*tp_compare*/ - (reprfunc)float_repr, /*tp_repr*/ + (reprfunc)float_repr, /*tp_repr*/ &float_as_number, /*tp_as_number*/ 0, /*tp_as_sequence*/ 0, /*tp_as_mapping*/ - (hashfunc)float_hash, /*tp_hash*/ + (hashfunc)float_hash, /*tp_hash*/ + 0, /*tp_call*/ + (reprfunc)float_str, /*tp_str*/ }; void |