Function

A function is a machine that takes in one thing and spits out another. [TODO gross definition]

Examples

The following lines of C++ code are a function

string reverseString(const string &s) { 
  string returnStr = ""; 
  for (int i = s.size() - 1; i >= 0; --i) { 
    returnStr.append(s[I]);
  }
  return returnStr;
}