Consider the following summation function in C++:

  size_t sum(const vector& values)
  {
     size_t sum = 0;
     for (size_t i=0; i < values.size(); ++i)
     {
        sum += values[i];
     }     
     return sum;
  }  

• the order to add numbers
• to execute the summation in sequence rather than concurrently

The culprit here is the language, which prevents you from specifying the solution as succintly and as precisely as you want. In Cat I would present the solution as follows:

  def sum : (list<int>) -> (int)
  {
     [+] reduce
  } 

   size_t sum(const vector<int>& values)
   {
      size_t sum = 0;
      for (size_t i=0; i < values.size(); ++i)
      {
         sum += values[i];
      }     
      return sum;
   }

int sum = accumulate(values.begin(), values.end(), 0);