// Stage 01: read one value, update one accumulator. Original teaching code.
#include <array>
#include <iostream>
int main() {
    // Five existing integers. Positions are 0, 1, 2, 3, 4.
    const std::array<int,5> readings{3,1,4,1,5};
    int total=0;
    for(const int reading:readings) {
        total+=reading; // After each pass: 3, 4, 8, 9, 14.
    }
    if(total!=14 || readings.size()!=5) return 1;
    int empty_total=0;
    for(const int reading:std::array<int,0>{}) empty_total+=reading;
    int single_total=0;
    for(const int reading:std::array<int,1>{5}) single_total+=reading;
    if(empty_total!=0 || single_total!=5) return 2;
    std::cout<<"count="<<readings.size()<<" total="<<total<<'\n';
    std::cout<<"empty="<<empty_total<<" single="<<single_total<<'\n';
}