readable.cpp

#include <cctype>
#include <iostream>
#include <type_traits>
#include <typeinfo>

namespace ascii
{
  template <typename T, T operand, typename std::enable_if<std::is_same<T,char>::value, int>::type = 0>
  class get_lower
  {
    public:
      explicit get_lower() : low_val{operand>='a' ? operand-('a'-'A') : operand}
      {
      }
      T value()
      {
        return low_val;
      }
    private:
      T low_val;
  };
}

int main()
{
	ascii::get_lower<char, 'c'> test;
	std::cout << test.value();
	return 0;
}