55 lines
2.1 KiB
C
55 lines
2.1 KiB
C
#ifndef CPPUNIT_PORTABILITY_FLOATINGPOINT_H_INCLUDED
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#define CPPUNIT_PORTABILITY_FLOATINGPOINT_H_INCLUDED
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#include <cppunit/Portability.h>
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#include <math.h>
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CPPUNIT_NS_BEGIN
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/// \brief Tests if a floating-point is a NaN.
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// According to IEEE-754 floating point standard,
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// (see e.g. page 8 of
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// http://www.cs.berkeley.edu/~wkahan/ieee754status/ieee754.ps)
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// all comparisons with NaN are false except "x != x", which is true.
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//
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// At least Microsoft Visual Studio 6 is known not to implement this test correctly.
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// It emits the following code to test equality:
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// fcomp qword ptr [nan]
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// fnstsw ax // copie fp (floating-point) status register to ax
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// test ah,40h // test bit 14 of ax (0x4000) => C3 of fp status register
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// According to the following documentation on the x86 floating point status register,
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// the C2 bit should be tested to test for NaN value.
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// http://webster.cs.ucr.edu/AoA/Windows/HTML/RealArithmetic.html#1000117
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// In Microsoft Visual Studio 2003 & 2005, the test is implemented with:
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// test ah,44h // Visual Studio 2005 test both C2 & C3...
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//
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// To work around this, a NaN is assumed to be detected if no strict ordering is found.
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inline bool floatingPointIsUnordered( double x )
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{
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// x != x will detect a NaN on conformant platform
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// (2.0 < x && x < 1.0) will detect a NaN on non conformant platform:
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// => no ordering can be found for x.
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return (x != x) || (2.0 < x && x < 1.0);
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}
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/// \brief Tests if a floating-point is finite.
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/// @return \c true if x is neither a NaN, nor +inf, nor -inf, \c false otherwise.
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inline int floatingPointIsFinite( double x )
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{
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#if defined(CPPUNIT_HAVE_ISFINITE)
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return isfinite( x );
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#elif defined(CPPUNIT_HAVE_FINITE)
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return finite( x );
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#elif defined(CPPUNIT_HAVE__FINITE)
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return _finite(x);
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#else
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double testInf = x * 0.0; // Produce 0.0 if x is finite, a NaN otherwise.
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return testInf == 0.0 && !floatingPointIsUnordered(testInf);
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#endif
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}
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CPPUNIT_NS_END
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#endif // CPPUNIT_PORTABILITY_FLOATINGPOINT_H_INCLUDED
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