QUIET_NAN.cpp

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// checking for quiet NaN
 
 
#include <stdlib.h>
 
#include "config.h"
 
 
int main ()
{
#ifdef _RWSTD_NO_DBL_TRAPS
 
    // if floating point arithmetic doesn't trap, compute
    // the result of (0.0 / 0.0) and exit successfully if
    // the value of the result is a QNAN
 
    char *endptr = 0;
 
    // NaN is never equal to another NaN
 
    // compute NAN by 0.0 / 0.0 using strtod to foil optimizers
    double nan_1 = strtod ("000", &endptr) / strtod ("0.0", &endptr);
    double nan_2 = strtod ("0.0", &endptr) / strtod ("000", &endptr);
 
    return !(nan_1 != nan_2);
 
#else   // if defined (_RWSTD_NO_DBL_TRAPS)
 
    // if floating point arithmetic traps assume QNAN exists
    return 0;
 
#endif   // _RWSTD_NO_DBL_TRAPS
 
}