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1
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2 /* Float object interface */
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3
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4 /*
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5 PyFloatObject represents a (double precision) floating point number.
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6 */
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7
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8 #ifndef Py_FLOATOBJECT_H
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9 #define Py_FLOATOBJECT_H
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10 #ifdef __cplusplus
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11 extern "C" {
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12 #endif
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13
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14 typedef struct {
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15 PyObject_HEAD
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16 double ob_fval;
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17 } PyFloatObject;
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18
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19 PyAPI_DATA(PyTypeObject) PyFloat_Type;
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20
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21 #define PyFloat_Check(op) PyObject_TypeCheck(op, &PyFloat_Type)
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22 #define PyFloat_CheckExact(op) (Py_TYPE(op) == &PyFloat_Type)
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23
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24 /* The str() precision PyFloat_STR_PRECISION is chosen so that in most cases,
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25 the rounding noise created by various operations is suppressed, while
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26 giving plenty of precision for practical use. */
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27
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28 #define PyFloat_STR_PRECISION 12
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29
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30 #ifdef Py_NAN
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31 #define Py_RETURN_NAN return PyFloat_FromDouble(Py_NAN)
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32 #endif
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33
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34 #define Py_RETURN_INF(sign) do \
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35 if (copysign(1., sign) == 1.) { \
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36 return PyFloat_FromDouble(Py_HUGE_VAL); \
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37 } else { \
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38 return PyFloat_FromDouble(-Py_HUGE_VAL); \
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39 } while(0)
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40
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41 PyAPI_FUNC(double) PyFloat_GetMax(void);
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42 PyAPI_FUNC(double) PyFloat_GetMin(void);
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43 PyAPI_FUNC(PyObject *) PyFloat_GetInfo(void);
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44
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45 /* Return Python float from string PyObject. Second argument ignored on
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46 input, and, if non-NULL, NULL is stored into *junk (this tried to serve a
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47 purpose once but can't be made to work as intended). */
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48 PyAPI_FUNC(PyObject *) PyFloat_FromString(PyObject*, char** junk);
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49
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50 /* Return Python float from C double. */
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51 PyAPI_FUNC(PyObject *) PyFloat_FromDouble(double);
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52
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53 /* Extract C double from Python float. The macro version trades safety for
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54 speed. */
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55 PyAPI_FUNC(double) PyFloat_AsDouble(PyObject *);
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56 #define PyFloat_AS_DOUBLE(op) (((PyFloatObject *)(op))->ob_fval)
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57
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58 /* Write repr(v) into the char buffer argument, followed by null byte. The
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59 buffer must be "big enough"; >= 100 is very safe.
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60 PyFloat_AsReprString(buf, x) strives to print enough digits so that
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61 PyFloat_FromString(buf) then reproduces x exactly. */
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62 PyAPI_FUNC(void) PyFloat_AsReprString(char*, PyFloatObject *v);
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63
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64 /* Write str(v) into the char buffer argument, followed by null byte. The
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65 buffer must be "big enough"; >= 100 is very safe. Note that it's
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66 unusual to be able to get back the float you started with from
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67 PyFloat_AsString's result -- use PyFloat_AsReprString() if you want to
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68 preserve precision across conversions. */
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69 PyAPI_FUNC(void) PyFloat_AsString(char*, PyFloatObject *v);
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70
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71 /* _PyFloat_{Pack,Unpack}{4,8}
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72 *
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73 * The struct and pickle (at least) modules need an efficient platform-
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74 * independent way to store floating-point values as byte strings.
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75 * The Pack routines produce a string from a C double, and the Unpack
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76 * routines produce a C double from such a string. The suffix (4 or 8)
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77 * specifies the number of bytes in the string.
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78 *
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79 * On platforms that appear to use (see _PyFloat_Init()) IEEE-754 formats
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80 * these functions work by copying bits. On other platforms, the formats the
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81 * 4- byte format is identical to the IEEE-754 single precision format, and
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82 * the 8-byte format to the IEEE-754 double precision format, although the
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83 * packing of INFs and NaNs (if such things exist on the platform) isn't
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84 * handled correctly, and attempting to unpack a string containing an IEEE
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85 * INF or NaN will raise an exception.
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86 *
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87 * On non-IEEE platforms with more precision, or larger dynamic range, than
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88 * 754 supports, not all values can be packed; on non-IEEE platforms with less
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89 * precision, or smaller dynamic range, not all values can be unpacked. What
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90 * happens in such cases is partly accidental (alas).
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91 */
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92
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93 /* The pack routines write 4 or 8 bytes, starting at p. le is a bool
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94 * argument, true if you want the string in little-endian format (exponent
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95 * last, at p+3 or p+7), false if you want big-endian format (exponent
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96 * first, at p).
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97 * Return value: 0 if all is OK, -1 if error (and an exception is
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98 * set, most likely OverflowError).
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99 * There are two problems on non-IEEE platforms:
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100 * 1): What this does is undefined if x is a NaN or infinity.
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101 * 2): -0.0 and +0.0 produce the same string.
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102 */
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103 PyAPI_FUNC(int) _PyFloat_Pack4(double x, unsigned char *p, int le);
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104 PyAPI_FUNC(int) _PyFloat_Pack8(double x, unsigned char *p, int le);
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105
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106 /* Used to get the important decimal digits of a double */
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107 PyAPI_FUNC(int) _PyFloat_Digits(char *buf, double v, int *signum);
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108 PyAPI_FUNC(void) _PyFloat_DigitsInit(void);
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109
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110 /* The unpack routines read 4 or 8 bytes, starting at p. le is a bool
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111 * argument, true if the string is in little-endian format (exponent
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112 * last, at p+3 or p+7), false if big-endian (exponent first, at p).
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113 * Return value: The unpacked double. On error, this is -1.0 and
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114 * PyErr_Occurred() is true (and an exception is set, most likely
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115 * OverflowError). Note that on a non-IEEE platform this will refuse
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116 * to unpack a string that represents a NaN or infinity.
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117 */
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118 PyAPI_FUNC(double) _PyFloat_Unpack4(const unsigned char *p, int le);
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119 PyAPI_FUNC(double) _PyFloat_Unpack8(const unsigned char *p, int le);
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120
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121 /* free list api */
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122 PyAPI_FUNC(int) PyFloat_ClearFreeList(void);
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123
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124 /* Format the object based on the format_spec, as defined in PEP 3101
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125 (Advanced String Formatting). */
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126 PyAPI_FUNC(PyObject *) _PyFloat_FormatAdvanced(PyObject *obj,
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127 char *format_spec,
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128 Py_ssize_t format_spec_len);
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129
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130 /* Round a C double x to the closest multiple of 10**-ndigits. Returns a
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131 Python float on success, or NULL (with an appropriate exception set) on
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132 failure. Used in builtin_round in bltinmodule.c. */
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133 PyAPI_FUNC(PyObject *) _Py_double_round(double x, int ndigits);
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134
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135
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136
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137 #ifdef __cplusplus
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138 }
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139 #endif
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140 #endif /* !Py_FLOATOBJECT_H */
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