Added zip() functionality for combining iterators.

source/mijin/util/iterators.hpp

@@ -169,6 +169,86 @@ Enumeratable<TIdx, TIterable> enumerate(TIterable&& iterable)
     return {.base = {std::forward<TIterable>(iterable)}};
 }
 
+template<typename TFirstIterator, typename TSecondIterator>
+struct ZippingIterator
+{
+    TFirstIterator first;
+    TSecondIterator second;
+
+    ZippingIterator(TFirstIterator first_, TSecondIterator second_) noexcept : first(first_), second(second_) {}
+    ZippingIterator(const ZippingIterator&) noexcept = default;
+
+    ZippingIterator& operator=(const ZippingIterator&) noexcept = default;
+
+    auto operator*() const noexcept
+    {
+        return std::tie(*first, *second);
+    }
+
+    ZippingIterator& operator++() noexcept
+    {
+        ++first;
+        ++second;
+        return *this;
+    }
+
+    ZippingIterator operator++(int) noexcept
+    {
+        ZippingIterator copy(*this);
+        ++(*this);
+        return copy;
+    }
+
+    ZippingIterator& operator--() noexcept
+    {
+        --first;
+        --second;
+        return *this;
+    }
+
+    ZippingIterator operator--(int) noexcept
+    {
+        ZippingIterator copy(*this);
+        --(*this);
+        return copy;
+    }
+
+    bool operator==(const ZippingIterator& other) const noexcept
+    {
+        return first == other.first || second == other.second; // note: this uses or so reaching the end on one range also ends the zipped one.
+    }
+
+    bool operator!=(const ZippingIterator& other) const noexcept
+    {
+        return !(*this == other);
+    }
+};
+template<typename TFirstIterator, typename TSecondIterator>
+ZippingIterator(TFirstIterator, TSecondIterator) -> ZippingIterator<TFirstIterator, TSecondIterator>;
+
+template<typename TFirst, typename TSecond>
+struct ZippingRange : RangeAdapter
+{
+    RangeRef<TFirst> first;
+    RangeRef<TSecond> second;
+
+    auto begin() const noexcept
+    {
+        return ZippingIterator(first.begin(), second.begin());
+    }
+
+    auto end() const noexcept
+    {
+        return ZippingIterator(first.end(), second.end());
+    }
+};
+
+template<typename TFirst, typename TSecond>
+ZippingRange<TFirst, TSecond> zip(TFirst&& first, TSecond&& second)
+{
+    return {.first = {std::forward<TFirst>(first)}, .second = {std::forward<TSecond>(second)}};
+}
+
 template<typename TIterator>
 struct ReplacingIterator
 {