readme-example.cpp

#include <ctpg/ctpg.hpp>
#include <iostream>

using namespace ctpg;
using namespace ctpg::buffers;

constexpr nterm<int> list("list");

constexpr char number_pattern[] = "[1-9][0-9]*";
constexpr regex_term<number_pattern> number("number");

constexpr int to_int(std::string_view sv)
{
    int sum = 0;
    for (auto c : sv) { sum *= 10; sum += c - '0'; }
    return sum;
}

constexpr parser p(
    list,
    terms(',', number),
    nterms(list),
    rules(
        list(number)
            >= to_int,
        list(list, ',', number)
            >= [](int sum, char, const auto& n){ return sum + to_int(n); }
    )
);

int main(int argc, char* argv[])
{
    if (argc < 2)
    {
        constexpr char example_text[] = "1, 2, 3";
        constexpr auto cres = p.parse(cstring_buffer(example_text));
        std::cout << cres.value() << std::endl;
        return 0;
    }

    auto res = p.parse(string_buffer(argv[1]), std::cerr);
    bool success = res.has_value();
    if (success)
        std::cout << res.value() << std::endl;
    return success ? 0 : -1;
}