A well-framed integral value to std::string function.

gistfile1.cpp

template <typename integral>
std::string to_string(integral value, int base = 10, bool lower_case = true) {
  const char * digit = lower_case ? "0123456789abcedfghijklmnopqrstuvwxyz"
      : "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
  
  assert(2 <= base && base <= 36);
  
  std::string str;
 
  bool negative = false;
 
  if (value < 0) {
    negative = true;
    value = -value;
  }
 
  do {
    str += digit[value % base];
    value /= base;
  } while (value != 0);
 
  if (negative)
    str += '-';
 
  std::reverse(str.begin(), str.end());
 
  return str;
}

Is it really well-framed?
I don't sure.
But I'd improve it.