constants.hpp

#ifndef PASTELSYS_CONSTANTS_HPP
#define PASTELSYS_CONSTANTS_HPP

#include "pastel/sys/math/constants.h"
#include "pastel/sys/ensure.h"
#include "pastel/sys/string/digit.h"

#include <sstream>
#include <string>

#include <cctype>

namespace Pastel
{

    template <
        typename Real,
        Requires<std::is_floating_point<Real>>>
    Real stringAsReal(const std::string& that)
    {
        std::stringstream stream(that);

        Real result = 0;
        stream >> result;

        return result;
    }

    template <
        typename Real,
        Requires<std::is_floating_point<Real>>>
    Real constantPi()
    {
        return 3.1415926535897932384626433832795;
    }

    template <
        typename Real,
        Requires<std::is_floating_point<Real>>>
    Real constantNeper()
    {
        return 2.7182818284590452353602874713527;
    }

    template <
        typename Real,
        Requires<std::is_floating_point<Real>>>
    Real constantLn2()
    {
        return 0.69314718055994530941723212145818;
    }

    template <
        typename Real,
        Requires<std::is_floating_point<Real>>>
    Real constantEulerMascheroni()
    {
        return 0.57721566490153286060651209008240;
    }

    /*
   template <typename Real>
   Real stringAsReal(
       const std::string& number,
       integer base)
   {
       ENSURE(!number.empty());

       std::size_t first = number.find_first_not_of(" ");

       ENSURE(first != std::string::npos);

       std::size_t last = number.find_first_of(" ", first);

       if (last == std::string::npos)
       {
           last = number.size();
       }

       // Examples of the allowed input:

       // "012345"
       // "-012345"
       // "+012345"
       // "012345."
       // "-012345."
       // "+012345."
       // " 012345.012345"
       // "-012345.012345"
       // "+012345.012345"
       // " .012345"
       // "-.012345"
       // "+.012345"

       std::string word(number.substr(first, last - first));

       ENSURE(!word.empty());

       integer length = word.size();
       integer signIndex = word.find_first_of("+-");
       integer dotIndex = word.find_first_of(".");

       if (signIndex == std::string::npos)
       {
           signIndex = -1;
       }

       if (dotIndex == std::string::npos)
       {
           dotIndex = length;
       }

       Real result(0);

       {
           Real unit(Real(1) / base);
           for (integer i = dotIndex + 1;i < length;++i)
           {
               result += unit * digitAsInteger(word.at(i));
               unit /= base;
           }
       }
       {
           Real unit(1);
           for (integer i = dotIndex - 1;i > signIndex;--i)
           {
               result += unit * digitAsInteger(word.at(i));
               unit *= base;
           }
       }

       if (signIndex != -1)
       {
           if (word.at(signIndex) == '-')
           {
               result = -result;
           }
       }

       return result;
   }
   */

}

#endif