سي99

#include <stdio.h>
#include <math.h>
#include <float.h>
#include <fenv.h>
#include <tgmath.h>
#include <stdbool.h>
#include <assert.h>
 
double compute_fn(double z) // [1]
{
    #pragma STDC FENV_ACCESS ON // [2]

    assert(FLT_EVAL_METHOD == 2); // [3]

    if (isnan(z)) // [4]
        puts("z is not a number");

    if (isinf(z))
        puts("z is infinite");

    long double r = 7.0 - 3.0/(z - 2.0 - 1.0/(z - 7.0 + 10.0/(z - 2.0 - 2.0/(z - 3.0)))); // [5, 6]

    feclearexcept(FE_DIVBYZERO); // [7]

    bool raised = fetestexcept(FE_OVERFLOW); // [8]

    if (raised)
        puts("Unanticipated overflow.");

    return r;
}

int main(void)
{
    #ifndef __STDC_IEC_559__
    puts("Warning: __STDC_IEC_559__ not defined. IEEE 754 floating point not fully supported."); // [9]
    #endif

    #pragma STDC FENV_ACCESS ON

    #ifdef TEST_NUMERIC_STABILITY_UP
    fesetround(FE_UPWARD);          // [10]
    #elif TEST_NUMERIC_STABILITY_DOWN
    fesetround(FE_DOWNWARD);
    #endif

    printf("%.7g\n", compute_fn(3.0));
    printf("%.7g\n", compute_fn(NAN));

    return 0;
}