summaryrefslogtreecommitdiffstats
path: root/Objects/floatobject.c
diff options
context:
space:
mode:
Diffstat (limited to 'Objects/floatobject.c')
-rw-r--r--Objects/floatobject.c117
1 files changed, 29 insertions, 88 deletions
diff --git a/Objects/floatobject.c b/Objects/floatobject.c
index 5cb3201..9b499ba 100644
--- a/Objects/floatobject.c
+++ b/Objects/floatobject.c
@@ -1066,20 +1066,19 @@ float_float(PyObject *v)
}
static PyObject *
-float_as_integer_ratio(PyObject *v)
+float_as_integer_ratio(PyObject *v, PyObject *unused)
{
double self;
double float_part;
int exponent;
- int is_negative;
- const int chunk_size = 28;
+ int i;
+
PyObject *prev;
- PyObject *py_chunk = NULL;
PyObject *py_exponent = NULL;
PyObject *numerator = NULL;
PyObject *denominator = NULL;
PyObject *result_pair = NULL;
- PyNumberMethods *long_methods;
+ PyNumberMethods *long_methods = PyLong_Type.tp_as_number;
#define INPLACE_UPDATE(obj, call) \
prev = obj; \
@@ -1101,93 +1100,31 @@ float_as_integer_ratio(PyObject *v)
}
#endif
- if (self == 0) {
- numerator = PyLong_FromLong(0);
- if (numerator == NULL) goto error;
- denominator = PyLong_FromLong(1);
- if (denominator == NULL) goto error;
- result_pair = PyTuple_Pack(2, numerator, denominator);
- /* Hand ownership over to the tuple. If the tuple
- wasn't created successfully, we want to delete the
- ints anyway. */
- Py_DECREF(numerator);
- Py_DECREF(denominator);
- return result_pair;
- }
-
- /* XXX: Could perhaps handle FLT_RADIX!=2 by using ilogb and
- scalbn, but those may not be in C89. */
PyFPE_START_PROTECT("as_integer_ratio", goto error);
- float_part = frexp(self, &exponent);
- is_negative = 0;
- if (float_part < 0) {
- float_part = -float_part;
- is_negative = 1;
- /* 0.5 <= float_part < 1.0 */
- }
+ float_part = frexp(self, &exponent); /* self == float_part * 2**exponent exactly */
PyFPE_END_PROTECT(float_part);
- /* abs(self) == float_part * 2**exponent exactly */
-
- /* Suck up chunk_size bits at a time; 28 is enough so that we
- suck up all bits in 2 iterations for all known binary
- double-precision formats, and small enough to fit in a
- long. */
- numerator = PyLong_FromLong(0);
+
+ for (i=0; i<300 && float_part != floor(float_part) ; i++) {
+ float_part *= 2.0;
+ exponent--;
+ }
+ /* self == float_part * 2**exponent exactly and float_part is integral.
+ If FLT_RADIX != 2, the 300 steps may leave a tiny fractional part
+ to be truncated by PyLong_FromDouble(). */
+
+ numerator = PyLong_FromDouble(float_part);
if (numerator == NULL) goto error;
- long_methods = PyLong_Type.tp_as_number;
-
- py_chunk = PyLong_FromLong(chunk_size);
- if (py_chunk == NULL) goto error;
-
- while (float_part != 0) {
- /* invariant: abs(self) ==
- (numerator + float_part) * 2**exponent exactly */
- long digit;
- PyObject *py_digit;
-
- PyFPE_START_PROTECT("as_integer_ratio", goto error);
- /* Pull chunk_size bits out of float_part, into digits. */
- float_part = ldexp(float_part, chunk_size);
- digit = (long)float_part;
- float_part -= digit;
- /* 0 <= float_part < 1 */
- exponent -= chunk_size;
- PyFPE_END_PROTECT(float_part);
-
- /* Shift digits into numerator. */
- // numerator <<= chunk_size
- INPLACE_UPDATE(numerator,
- long_methods->nb_lshift(numerator, py_chunk));
- if (numerator == NULL) goto error;
-
- // numerator |= digit
- py_digit = PyLong_FromLong(digit);
- if (py_digit == NULL) goto error;
- INPLACE_UPDATE(numerator,
- long_methods->nb_or(numerator, py_digit));
- Py_DECREF(py_digit);
- if (numerator == NULL) goto error;
- }
-
- /* Add in the sign bit. */
- if (is_negative) {
- INPLACE_UPDATE(numerator,
- long_methods->nb_negative(numerator));
- if (numerator == NULL) goto error;
- }
-
- /* now self = numerator * 2**exponent exactly; fold in 2**exponent */
+ /* fold in 2**exponent */
denominator = PyLong_FromLong(1);
- py_exponent = PyLong_FromLong(labs(exponent));
+ py_exponent = PyLong_FromLong(labs((long)exponent));
if (py_exponent == NULL) goto error;
INPLACE_UPDATE(py_exponent,
long_methods->nb_lshift(denominator, py_exponent));
if (py_exponent == NULL) goto error;
if (exponent > 0) {
INPLACE_UPDATE(numerator,
- long_methods->nb_multiply(numerator,
- py_exponent));
+ long_methods->nb_multiply(numerator, py_exponent));
if (numerator == NULL) goto error;
}
else {
@@ -1196,12 +1133,17 @@ float_as_integer_ratio(PyObject *v)
py_exponent = NULL;
}
+ /* Returns ints instead of longs where possible */
+ INPLACE_UPDATE(numerator, PyNumber_Int(numerator));
+ if (numerator == NULL) goto error;
+ INPLACE_UPDATE(denominator, PyNumber_Int(denominator));
+ if (denominator == NULL) goto error;
+
result_pair = PyTuple_Pack(2, numerator, denominator);
#undef INPLACE_UPDATE
error:
Py_XDECREF(py_exponent);
- Py_XDECREF(py_chunk);
Py_XDECREF(denominator);
Py_XDECREF(numerator);
return result_pair;
@@ -1210,17 +1152,16 @@ error:
PyDoc_STRVAR(float_as_integer_ratio_doc,
"float.as_integer_ratio() -> (int, int)\n"
"\n"
-"Returns a pair of integers, not necessarily in lowest terms, whose\n"
-"ratio is exactly equal to the original float. This method raises an\n"
-"OverflowError on infinities and a ValueError on nans. The resulting\n"
-"denominator will be positive.\n"
+"Returns a pair of integers, whose ratio is exactly equal to the original\n"
+"float and with a positive denominator.\n"
+"Raises OverflowError on infinities and a ValueError on nans.\n"
"\n"
">>> (10.0).as_integer_ratio()\n"
-"(167772160L, 16777216L)\n"
+"(10, 1)\n"
">>> (0.0).as_integer_ratio()\n"
"(0, 1)\n"
">>> (-.25).as_integer_ratio()\n"
-"(-134217728L, 536870912L)");
+"(-1, 4)");
static PyObject *