BOOST_FOREACHに添え字を付けてみた

手段と目的が交差するとき、無駄努力が始まる。
ほしいという声を聞いたので、BOOST_FOEACHという素材を活かす方向でなんとか。

#include <iostream>

#include <vector>

#include <boost/foreach.hpp>

#include <boost/preprocessor/cat.hpp>

#include <boost/assign/std/vector.hpp>
#define INDEX_FOREACH(elem, cont, n) \

    INDEX_FOREACH_I(elem, cont, n, BOOST_PP_CAT(_index_foreach_label_, __LINE__))

#define INDEX_FOREACH_I(elem, cont, n, label) \

    if (bool _index_foreach_break = false) {} else \

    if (size_t _index_foreach_index = 0) {} else \

    label: \

    if (_index_foreach_break) {} else \

    BOOST_FOREACH(elem, cont) \

    for (bool _index_foreach_flag = true; \

         _index_foreach_flag; \

         _index_foreach_flag && (_index_foreach_break = true)) \

    if (_index_foreach_break) { goto label; } else \

    for (n = _index_foreach_index; \

         _index_foreach_flag; \

         ++_index_foreach_index, _index_foreach_flag = false)
struct hoge {

    int n;

    hoge(int n) : n(n) {}

};
int main() {

    int ar[] = {10,20,30,40,50,60};

    INDEX_FOREACH (int n, ar, size_t i) {

        if (i == 2) continue;

        std::cout << i << ": " << n << '\n';

        if (i == 4) break;

    }
    std::cout << "-------------------\n";
    using boost::assign::operator+=;

    std::vector<hoge> v;

    v += 20,40,60,60,80,100;

    INDEX_FOREACH (hoge const & x, v, size_t i) {

        if (i % 2) continue;

        std::cout << i << ": " << x.n << '\n';

        break;

    }

}

結果：http://ideone.com/BcH8i
書きながらこれでいいんじゃないかと思った。