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206 lines
8.4 KiB
C
206 lines
8.4 KiB
C
#ifndef Py_INTERNAL_PYMATH_H
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#define Py_INTERNAL_PYMATH_H
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#ifdef __cplusplus
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extern "C" {
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#endif
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#ifndef Py_BUILD_CORE
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# error "this header requires Py_BUILD_CORE define"
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#endif
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/* _Py_ADJUST_ERANGE1(x)
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* _Py_ADJUST_ERANGE2(x, y)
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* Set errno to 0 before calling a libm function, and invoke one of these
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* macros after, passing the function result(s) (_Py_ADJUST_ERANGE2 is useful
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* for functions returning complex results). This makes two kinds of
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* adjustments to errno: (A) If it looks like the platform libm set
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* errno=ERANGE due to underflow, clear errno. (B) If it looks like the
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* platform libm overflowed but didn't set errno, force errno to ERANGE. In
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* effect, we're trying to force a useful implementation of C89 errno
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* behavior.
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* Caution:
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* This isn't reliable. C99 no longer requires libm to set errno under
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* any exceptional condition, but does require +- HUGE_VAL return
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* values on overflow. A 754 box *probably* maps HUGE_VAL to a
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* double infinity, and we're cool if that's so, unless the input
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* was an infinity and an infinity is the expected result. A C89
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* system sets errno to ERANGE, so we check for that too. We're
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* out of luck if a C99 754 box doesn't map HUGE_VAL to +Inf, or
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* if the returned result is a NaN, or if a C89 box returns HUGE_VAL
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* in non-overflow cases.
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*/
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static inline void _Py_ADJUST_ERANGE1(double x)
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{
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if (errno == 0) {
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if (x == Py_INFINITY || x == -Py_INFINITY) {
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errno = ERANGE;
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}
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}
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else if (errno == ERANGE && x == 0.0) {
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errno = 0;
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}
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}
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static inline void _Py_ADJUST_ERANGE2(double x, double y)
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{
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if (x == Py_INFINITY || x == -Py_INFINITY ||
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y == Py_INFINITY || y == -Py_INFINITY)
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{
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if (errno == 0) {
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errno = ERANGE;
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}
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}
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else if (errno == ERANGE) {
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errno = 0;
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}
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}
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//--- HAVE_PY_SET_53BIT_PRECISION macro ------------------------------------
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//
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// The functions _Py_dg_strtod() and _Py_dg_dtoa() in Python/dtoa.c (which are
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// required to support the short float repr introduced in Python 3.1) require
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// that the floating-point unit that's being used for arithmetic operations on
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// C doubles is set to use 53-bit precision. It also requires that the FPU
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// rounding mode is round-half-to-even, but that's less often an issue.
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//
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// If your FPU isn't already set to 53-bit precision/round-half-to-even, and
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// you want to make use of _Py_dg_strtod() and _Py_dg_dtoa(), then you should:
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//
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// #define HAVE_PY_SET_53BIT_PRECISION 1
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//
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// and also give appropriate definitions for the following three macros:
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//
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// * _Py_SET_53BIT_PRECISION_HEADER: any variable declarations needed to
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// use the two macros below.
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// * _Py_SET_53BIT_PRECISION_START: store original FPU settings, and
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// set FPU to 53-bit precision/round-half-to-even
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// * _Py_SET_53BIT_PRECISION_END: restore original FPU settings
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//
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// The macros are designed to be used within a single C function: see
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// Python/pystrtod.c for an example of their use.
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// Get and set x87 control word for gcc/x86
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#ifdef HAVE_GCC_ASM_FOR_X87
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#define HAVE_PY_SET_53BIT_PRECISION 1
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// Functions defined in Python/pymath.c
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extern unsigned short _Py_get_387controlword(void);
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extern void _Py_set_387controlword(unsigned short);
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#define _Py_SET_53BIT_PRECISION_HEADER \
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unsigned short old_387controlword, new_387controlword
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#define _Py_SET_53BIT_PRECISION_START \
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do { \
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old_387controlword = _Py_get_387controlword(); \
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new_387controlword = (old_387controlword & ~0x0f00) | 0x0200; \
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if (new_387controlword != old_387controlword) { \
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_Py_set_387controlword(new_387controlword); \
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} \
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} while (0)
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#define _Py_SET_53BIT_PRECISION_END \
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do { \
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if (new_387controlword != old_387controlword) { \
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_Py_set_387controlword(old_387controlword); \
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} \
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} while (0)
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#endif
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// Get and set x87 control word for VisualStudio/x86.
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// x87 is not supported in 64-bit or ARM.
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#if defined(_MSC_VER) && !defined(_WIN64) && !defined(_M_ARM)
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#define HAVE_PY_SET_53BIT_PRECISION 1
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#include <float.h> // __control87_2()
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#define _Py_SET_53BIT_PRECISION_HEADER \
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unsigned int old_387controlword, new_387controlword, out_387controlword
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// We use the __control87_2 function to set only the x87 control word.
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// The SSE control word is unaffected.
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#define _Py_SET_53BIT_PRECISION_START \
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do { \
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__control87_2(0, 0, &old_387controlword, NULL); \
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new_387controlword = \
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(old_387controlword & ~(_MCW_PC | _MCW_RC)) | (_PC_53 | _RC_NEAR); \
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if (new_387controlword != old_387controlword) { \
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__control87_2(new_387controlword, _MCW_PC | _MCW_RC, \
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&out_387controlword, NULL); \
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} \
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} while (0)
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#define _Py_SET_53BIT_PRECISION_END \
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do { \
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if (new_387controlword != old_387controlword) { \
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__control87_2(old_387controlword, _MCW_PC | _MCW_RC, \
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&out_387controlword, NULL); \
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} \
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} while (0)
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#endif
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// MC68881
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#ifdef HAVE_GCC_ASM_FOR_MC68881
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#define HAVE_PY_SET_53BIT_PRECISION 1
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#define _Py_SET_53BIT_PRECISION_HEADER \
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unsigned int old_fpcr, new_fpcr
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#define _Py_SET_53BIT_PRECISION_START \
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do { \
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__asm__ ("fmove.l %%fpcr,%0" : "=g" (old_fpcr)); \
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/* Set double precision / round to nearest. */ \
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new_fpcr = (old_fpcr & ~0xf0) | 0x80; \
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if (new_fpcr != old_fpcr) { \
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__asm__ volatile ("fmove.l %0,%%fpcr" : : "g" (new_fpcr));\
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} \
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} while (0)
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#define _Py_SET_53BIT_PRECISION_END \
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do { \
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if (new_fpcr != old_fpcr) { \
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__asm__ volatile ("fmove.l %0,%%fpcr" : : "g" (old_fpcr)); \
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} \
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} while (0)
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#endif
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// Default definitions are empty
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#ifndef _Py_SET_53BIT_PRECISION_HEADER
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# define _Py_SET_53BIT_PRECISION_HEADER
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# define _Py_SET_53BIT_PRECISION_START
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# define _Py_SET_53BIT_PRECISION_END
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#endif
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//--- _PY_SHORT_FLOAT_REPR macro -------------------------------------------
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// If we can't guarantee 53-bit precision, don't use the code
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// in Python/dtoa.c, but fall back to standard code. This
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// means that repr of a float will be long (17 significant digits).
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//
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// Realistically, there are two things that could go wrong:
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//
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// (1) doubles aren't IEEE 754 doubles, or
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// (2) we're on x86 with the rounding precision set to 64-bits
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// (extended precision), and we don't know how to change
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// the rounding precision.
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#if !defined(DOUBLE_IS_LITTLE_ENDIAN_IEEE754) && \
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!defined(DOUBLE_IS_BIG_ENDIAN_IEEE754) && \
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!defined(DOUBLE_IS_ARM_MIXED_ENDIAN_IEEE754)
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# define _PY_SHORT_FLOAT_REPR 0
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#endif
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// Double rounding is symptomatic of use of extended precision on x86.
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// If we're seeing double rounding, and we don't have any mechanism available
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// for changing the FPU rounding precision, then don't use Python/dtoa.c.
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#if defined(X87_DOUBLE_ROUNDING) && !defined(HAVE_PY_SET_53BIT_PRECISION)
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# define _PY_SHORT_FLOAT_REPR 0
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#endif
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#ifndef _PY_SHORT_FLOAT_REPR
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# define _PY_SHORT_FLOAT_REPR 1
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#endif
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#ifdef __cplusplus
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}
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#endif
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#endif /* !Py_INTERNAL_PYMATH_H */
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