ZIP

What

An implementation of zip for C++17. Single header file.

Why

Learning purposes.

Status

In development. Needs proper testing.

Install

Integrate with CMake or just copy the header file.

Usage and Documentation

#include <msd/zip.hpp>

#include <algorithm>
#include <cassert>
#include <vector>

int main() {
    std::vector actual_numbers = {1, 2, 3};
    std::vector expected_numbers = {1, 2, 3};

    const std::size_t size = std::min(actual_numbers.size(), expected_numbers.size());
    for (std::size_t i = 0; i < size; ++i) {
        assert(actual_numbers[i] == expected_numbers[i]);
    }

    // vs

    for (auto [actual, expected] : msd::zip(actual_numbers, expected_numbers)) {
        assert(actual == expected);
    }
}

For more, see tests and documentation.

Known issues

Calling std::prev on an msd::zip object compiles, but fails at runtime on some std containers.

• list
• forward_list
• unordered_set
• unordered_multiset
• unordered_map
• unordered_multimap

The msd::zip iterator is bidirectional to better control when you want to stop iterating.

To get only some of the elements from a C++23 zip, you can use std::views::take:

std::forward_list<int> first_list{1, 2, 3, 4, 5};
std::forward_list<int> second_list{1, 2, 3, 4};
auto forward_zip = std::views::zip(first_list, second_list);

for (auto [a, b] : forward_zip | std::views::take(3)) {
    std::cout << a << ", " << b << "\n";
}

With msd::zip, you can write:

for (auto it = forward_zip.begin(); it != std::prev(forward_zip.end()); ++it) {
    auto [a, b] = *it;
    std::cout << a << ", " << b << "\n";
}

But it does not work with the mentioned containers.

Post-increment operator missing

// Working
for (auto it = zip.begin(); it != zip.end(); ++it) {}

// Not working
for (auto it = zip.begin(); it != zip.end(); it++) {}

Development

Tools

• SSH keys for GitHub (~/.ssh)
• VS Code (see .vscode/extensions.json)
• Docker

Actions

• Debug: F5
• Coverage: Ctrl + Shift + P -> Run Task -> Generate Coverage Report
  • Show coverage inline: Ctrl + Shift + 7 OR Ctrl + Shift + P -> Coverage Gutters: Display Coverage
  • Coverage as HTML: See build/coverage_html/index.html
• Clang tidy: Ctrl + Shift + P -> Run Task -> Run clang-tidy on current file
• Documentation: Ctrl + Shift + P -> Run Task -> Generate Documentation

TODO

• Set up cache for release workflow (apt cache)
• Exception guarantees: set and document
• constexpr
• Write benchmarks
• Ignore google headers from clang-tidy
• Consider checked access that returns an optional reference
• Run clang-tidy on file save
• Cancel running jobs on new commit
• Investigate possible documentation issue: cp: no such file or directory
• Test
  • Analyze if LCOV_EXCL_LINE is needed
  • Iterator operations: +, -, +=, -=, ++ pre/post, --pre/post, std::prev/next/advance, begin() + size() - begin(), etc.