further clarification if possible:
why the 2 lines that don't compile:
// float128 e1 = exp(1.Q); // Note argument to exp is type float128.
// std::cout << e1 << std::endl; // 2.71828182845904523536028747135266231
if i put them in the following code compile regularly?
#include <iomanip>
#include <iostream>
#include <boost/cstdfloat.hpp> // For float_64_t, float128_t. Must be first
include!
#include <boost/multiprecision/float128.hpp>
#include <boost/math/special_functions.hpp> // For gamma function.
#include <boost/math/constants/constants.hpp> // For constants pi, e ...
#include <typeinfo>
#include <cmath> // for pow function.
using namespace std;
int main()
{
using boost::multiprecision::float128;
// Operations at 128-bit precision and full numeric_limits support:
float128 b = 2;
// There are 113-bits of precision:
std::cout << std::numeric_limits<float128>::digits << std::endl;
// Or 34 decimal places:
std::cout << std::numeric_limits<float128>::digits10 << std::endl;
// We can use any C++ std lib function, lets print all the digits as well:
std::cout << std::setprecision(std::numeric_limits<float128>::max_digits10)
<< log(b) << std::endl; // print log(2) = 0.693147180559945309417232121458176575
// We can also use any function from Boost.Math:
std::cout << boost::math::tgamma(b) << std::endl;
// And since we have an extended exponent range we can generate some really
large
// numbers here (4.02387260077093773543702433923004111e+2564):
std::cout << boost::math::tgamma(float128(1000)) << std::endl;
//
// We can declare constants using GCC or Intel's native types, and the Q
suffix,
// these can be declared constexpr if required:
constexpr float128 pi =
3.1415926535897932384626433832795028841971693993751058Q;
float128 e1 = exp(1.Q); // Note argument to exp is type float128.
std::cout << e1 << std::endl; // 2.71828182845904523536028747135266231
cout << "pi = " << pi << endl;
cout << "e1 = " << e1 << endl;
return 0;
}
> Executing task: ./main <
113
33
0.693147180559945309417232121458176575
1
4.02387260077093773543702433923004111e+2564
2.71828182845904523536028747135266231
pi = 3.1415926535897932384626433832795028
e1 = 2.71828182845904523536028747135266231
Thanks
> Il giorno 21 lug 2021, alle ore 19:14, Stefano Gragnani
> <stefano.gragn...@gmail.com> ha scritto:
>
> // float128 e1 = exp(1.Q); // Note argument to exp is type float128.
> // std::cout << e1 << std::endl; // 2.71828182845904523536028747135266231
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