it uses absolute difference epsilon equality ('close enough to be considered equal'):

    static int pretty_float_equal (float a, float b) { return fabsf(a - b) < FLT_EPSILON; }
    static int pretty_double_equal (double a, double b) { return fabs(a - b) < DBL_EPSILON; }
    static int pretty_long_double_equal (long double a, long double b) { return fabsl(a - b) < LDBL_EPSILON; }