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markpapadakis/transduders.cpp

Created February 6, 2019 14:07
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  1. markpapadakis created this gist Feb 6, 2019.
    104 changes: 104 additions & 0 deletions transduders.cpp
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,104 @@
    int main(int argc, char *argv[]) {
    std::vector<unsigned> arr{1, 2, 3, 4}, out;

    const auto reduce = [](auto it, const auto end,
    auto &&f, auto &&result) {
    using lambda_t = decltype(f);
    using value_t = typename std::remove_reference<decltype(*it)>::type;
    using res_t = typename std::result_of<lambda_t(decltype(result), value_t)>::type;

    while (it != end) {
    result = f(result, *it);
    ++it;
    }

    return result;
    };

    const auto map = [&](auto &&f, auto &col) {
    using value_t = typename std::remove_reference<decltype(col.front())>::type;

    return reduce(col.begin(), col.end(),
    [&f](auto &&result, const auto x) {
    result.push_back(f(x));
    return result;
    },
    std::vector<value_t>{});
    };

    const auto mapper = [](auto &&f) {
    return [&f](auto &&result, const auto x) {
    result.push_back(f(x));
    return result;
    };
    };

    const auto MAPPER = [](auto &&f) {
    return [&f](auto &&combine) {
    return [&f, &combine](auto &&result, const auto x) {
    return combine(result, f(x));
    };
    };
    };

    const auto append = [](auto &&arr, const auto x) {
    arr.push_back(x);
    return arr;
    };

    const auto V = reduce(arr.begin(), arr.end(),
    [](auto &&a, const auto x) { a.push_back(x + 1); return a; },
    std::vector<uint32_t>{});

    Print("V:", values_repr(V.data(), V.size()), "\n");

    const auto v2 = map([](const auto x) { return x + 1; }, arr);

    SLog("v2:", values_repr(v2.data(), v2.size()), "\n");

    const auto v3 = reduce(arr.begin(), arr.end(),
    mapper([](const auto x) { return x + 1; }), std::vector<uint32_t>{});

    SLog("v3:", values_repr(v3.data(), v3.size()), "\n");

    const auto v4 = reduce(arr.begin(), arr.end(),
    MAPPER([](const auto x) { return x + 1; })(append), std::vector<uint32_t>{});

    SLog("v4:", values_repr(v4.data(), v4.size()), "\n");

    const auto v5 = reduce(arr.begin(), arr.end(),
    MAPPER([](const auto x) { return x * 2; })(
    MAPPER([](const auto x) { return x + 1; })(append)),
    std::vector<uint32_t>());

    SLog("v5:", values_repr(v5.data(), v5.size()), "\n");

    const auto filterer = [](auto &&f) {
    return [&f](auto &&combine) {
    return [&combine, &f](auto &&result, const auto x) {
    return f(x) ? combine(result, x) : result;
    };
    };
    };

    auto v51 = reduce(arr.begin(), arr.end(),
    filterer([](const auto x) { return x > 2; })(append), std::vector<uint32_t>{});

    auto v6 = reduce(arr.begin(), arr.end(),
    filterer([](const auto x) { return x > 2; })(
    MAPPER([](const auto x) { return x * 2; })(append)),
    std::vector<uint32_t>{});

    SLog("v6:", values_repr(v6.data(), v6.size()), "\n");

    #if 0
    auto v7 = reduce(arr.begin(), arr.end(),
    compose(
    filterer([](const auto x) { return x > 2; }),
    MAPPER([](const auto x) { return x * 2; })
    )(append),
    std::vector<uint32_t>{});
    #endif

    return 0;
    }