Templates

Non-Type Templates

Templates can also take small compile-time values, such as an array size.

non-type parameter A non-type template parameter is a value known at compile time, like the `Size` in `std::array<int, Size>`.

Non-Type Templates

start
non_type_templates.cpp
Replay: real traced execution (multi-file project)
#include <array>
#include <iostream>

template <int Size>
int fillAndSum(int start) {
    std::array<int, Size> values{};
    int total = 0;

    for (int index = 0; index < Size; index++) {
        values[index] = start + index;
        total += values[index];
    }

    return total;
}

int main() {
    int start = 4;

    int total = fillAndSum<3>(start);

    std::cout << "size=3" << std::endl;
    std::cout << "start=" << start << std::endl;
    std::cout << "total=" << total << std::endl;
    return 0;
}

#include <array>
#include <iostream>

template <int Size>
int fillAndSum(int start) {
    std::array<int, Size> values{};
    int total = 0;

    for (int index = 0; index < Size; index++) {
        values[index] = start + index;
        total += values[index];
    }

    return total;
}

int main() {
    int start = 1;

    int total = fillAndSum<3>(start);

    std::cout << "size=3" << std::endl;
    std::cout << "start=" << start << std::endl;
    std::cout << "total=" << total << std::endl;
    return 0;
}

#include <array>
#include <iostream>

template <int Size>
int fillAndSum(int start) {
    std::array<int, Size> values{};
    int total = 0;

    for (int index = 0; index < Size; index++) {
        values[index] = start + index;
        total += values[index];
    }

    return total;
}

int main() {
    int start = 10;

    int total = fillAndSum<3>(start);

    std::cout << "size=3" << std::endl;
    std::cout << "start=" << start << std::endl;
    std::cout << "total=" << total << std::endl;
    return 0;
}

  1. start ← 4, total ← 15

    17int main() {18    int start→ 4 = 4; //@start=1, 101920    int total→ 15 = fillAndSum<3>(start4);2122    std::cout << "size=3" << std::endl;23    std::cout << "start=" << start4 << std::endl;24    std::cout << "total=" << total15 << std::endl;25    return 0;26}
    outputsize=3
start=4
total=15

  1. start ← 1, total ← 6

    17int main() {18    int start→ 1 = 1;1920    int total→ 6 = fillAndSum<3>(start1);2122    std::cout << "size=3" << std::endl;23    std::cout << "start=" << start1 << std::endl;24    std::cout << "total=" << total6 << std::endl;25    return 0;26}
    outputsize=3
start=1
total=6

  1. start ← 10, total ← 33

    17int main() {18    int start→ 10 = 10;1920    int total→ 33 = fillAndSum<3>(start10);2122    std::cout << "size=3" << std::endl;23    std::cout << "start=" << start10 << std::endl;24    std::cout << "total=" << total33 << std::endl;25    return 0;26}
    outputsize=3
start=10
total=33