C++ How to cin a char as a number instead of character

Question

I find myself often using variables that contain a very small range of numbers (typically from 1 to 10) and would like to minimize the amount of memory I use by using the char data type instead of int or even short. I would like to cin values to my char variables without having cin converting it to it's ASCII equivalent and without working with single quotes. Ie, the following:

cout<< "Pick from 1 to 10.";

char selection;

cin>> selection;

if (selection == 1) return 1;

etc...

Is there a common way of doing this? Again, I don't want to use single quotes.

Thanks

Answer 1

You can create a little utility function:

struct CharReader {
  char &c;
  CharReader(char &c) : c(c) {}
};

CharReader asNumber(char &c) {
  return CharReader(c);
}

template <typename T, typename Traits>
std::basic_istream<T, Traits>& operator>> (std::basic_istream<T, Traits> &str, const CharReader &c) {
  short i;
  str >> i;
  c.c = static_cast<char>(i);
  return str;
}

You can the use it like this:

char selection;
std::cin >> asNumber(selection);

Answer 2

There is no point in saving three bytes (or zero, because it's likely the compiler will align the stack anyway...) and complicating your code to read a number. Just do it normally and put your memory-saving efforts where it matters (if you don't know where it matters, it probably doesn't matter).

int selection;
if(!(cin >> selection) || selection < 0 || selection > 10) {
    // hmmm do something about it; perhaps scold the user.
}
place_where_it_is_getting_stored = selection;

Answer 3

char selection;
cin >> selection;
selection -= '0';