diff options
Diffstat (limited to 'Objects/floatobject.c')
-rw-r--r-- | Objects/floatobject.c | 117 |
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 * |