john <john@no.spamwrites:
Quote:
The code:
>
#include <iostream>
#include <limits>
>
>
int main()
{
using namespace std;
>
typedef numeric_limits<floatlimitsf;
>
cout<< boolalpha<< " radix= "<< limitsf::radix<< endl
<<" digits= "<< limitsf::digits<< endl
<< " digits10= "<< limitsf::digits10<< endl
<< " min()= "<< limitsf::min()<< endl
<< " max()= "<< limitsf::max()<< endl
<< " epsilon()= "<< limitsf::epsilon()<< endl
<< " min_exponent= "<< limitsf::min_exponent<< endl
<< " min_exponent10= "<< limitsf::min_exponent10<< endl
<< " max_exponent= "<< limitsf::max_exponent<< endl
<< " max_exponent10= "<< limitsf::max_exponent10<< endl
<< " is_iec559= "<< limitsf::is_iec559<< endl
<< " traps= "<< limitsf::traps<< endl;
>
}
>
>
in my system produces:
>
>
[john@localhost src]$ ./foobar-cpp
radix= 2
digits= 24
digits10= 6
min()= 1.17549e-38
max()= 3.40282e+38
epsilon()= 1.19209e-07
min_exponent= -125
min_exponent10= -37
max_exponent= 128
max_exponent10= 38
is_iec559= true
traps= false
That looks wrong to me. I think min_exponent should be -126. On my
system, this program
#include <iostream>
#include <limits>
template <typename float_t, typename sint_t, typename uint_t, int mbits, int ebits>
class ieee_float {
#ifdef __BIG_ENDIAN__
uint_t s:1;
uint_t e:ebits;
uint_t m:mbits;
#else
uint_t m:mbits;
uint_t e:ebits;
uint_t s:1;
#endif
public:
static const uint_t mdenom = ((uint_t)1 << mbits);
static const uint_t ebias = ((uint_t)1 << (ebits - 1)) - 1;
sint_t sign(void) const { return 1 - 2*s; }
sint_t exponent(void) const { return e ? e - ebias : -(ebias - 1); }
uint_t mantissa(void) const { return ((uint_t)(!!e) << mbits) | m; }
bool infinity(void) const { return (e == ((1 << ebits) - 1)) && (m == 0); }
bool nan(void) const { return (e == ((1 << ebits) - 1)) && (m != 0); }
bool denormal(void) const { return (e == 0) && (m != 0); }
ieee_float(float_t f) { *(float_t *)this = f; }
ieee_float(uint_t u) { *(uint_t *)this = u; }
operator float_t() const { return *(float_t *)this; }
operator uint_t() const { return *(uint_t *)this; }
};
typedef ieee_float<float, int, unsigned, 23, 8single_precision;
typedef ieee_float<double, long long, unsigned long long, 52, 11double_precision;
int main(int argc, char *argv[])
{
single_precision d(std::numeric_limits<float>::min());
std::cout << "decimal: " << (float) d << std::endl;
std::cout << "hexadecimal: " << std::hex << (unsigned) d << std::dec << std::endl;
std::cout << "sign: " << d.sign() << std::endl;
std::cout << "exponent: " << d.exponent() << std::endl;
std::cout << "mantissa: " << d.mantissa() << "/" << d.mdenom << std::endl;
std::cout << "min exponent: " << std::numeric_limits<float>::min_exponent << std::endl;
return 0;
}
produced this output:
$ ./test
decimal: 1.17549e-38
hexadecimal: 800000
sign: 1
exponent: -126
mantissa: 8388608/8388608
min exponent: -125
Strange that the exponent on "std::numeric_limits<float>::min()" would
be less than "std::numeric_limits<float>::min_exponent".
Chip
--
Charles M. "Chip" Coldwell
"Turn on, log in, tune out"
Somerville, Massachusetts, New England
