C++ Delivery Manifest Project

Your brief

Define a deliberately small manifest format: a nonempty stop token without commas, then one comma, then a parcel count from zero through one thousand. The numeric field uses exact decimal conversion with no whitespace. This is not general CSV: quoted fields, embedded separators and multiline records require a format-aware parser. Return an optional owned record so failed parsing cannot leave a partially updated caller object. Validate framing and the entire number before constructing the accepted result.

Run it locally

Use a C++20 compiler and matching standard library in a separate lab folder. The command uses c++; substitute g++, clang++ or zig c++ for your toolchain. C++ does not currently run in Bhylu’s browser playground. Apache, PHP and MySQL are not needed.

c++ -std=c++20 -Wall -Wextra -Wpedantic -Werror manifest-project.cpp -o lesson

On Windows use -o lesson.exe and run .\lesson.exe in PowerShell. On Unix-like systems run ./lesson. Thread examples may need -pthread on your platform.

Download the complete C++ source. Run file labs in a private empty directory, away from existing reports.

Worked solution

#include <iostream>
#include <string>
#include <string_view>
#include <optional>
#include <charconv>
#include <system_error>

struct StopRecord { std::string name; int parcels; };
std::optional<StopRecord> parse_stop(std::string_view line) {
    auto comma = line.find(',');
    if (comma == std::string_view::npos || comma == 0 || comma + 1 == line.size()) { return std::nullopt; }
    auto text = line.substr(comma + 1);
    int count{};
    auto [end, error] = std::from_chars(text.data(), text.data() + text.size(), count);
    if (error != std::errc{} || end != text.data() + text.size() || count < 0 || count > 1000) { return std::nullopt; }
    return StopRecord{std::string{line.substr(0, comma)}, count};
}

int main() {
    auto record = parse_stop("Quay,12");
    if (!record) { return 1; }
    std::cout << record->name << ": " << record->parcels << '\n';
    std::cout << "Junk accepted: " << parse_stop("Quay,12x").has_value() << '\n';
}

Quay: 12
Junk accepted: 0

Extend and test

Test missing separators, an empty name, missing count, negative and excessive counts, extra commas and oversized integer text. State the grammar before adding spaces or quoted names.