avoid complicate iterator operation

luk036 · Jan 28, 2024 · fa6d256 · fa6d256
1 parent 4559aed
commit fa6d256
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Showing 2 changed files with 11 additions and 11 deletions.
diff --git a/include/recti/polygon.hpp b/include/recti/polygon.hpp
@@ -53,13 +53,14 @@ namespace recti {
          * @return T
          */
         constexpr auto signed_area_x2() const -> T {
-            auto first = this->_vecs.begin();
-            auto second = std::next(first);
+            auto itr2 = this->_vecs.begin();
+            auto itr0 = itr2++;
+            auto itr1 = itr2++;
             auto end = this->_vecs.end();
             auto last = std::prev(end);
-            auto res = first->x() * second->y() - last->x() * std::prev(last)->y();
-            for (auto itr = second; itr != last; ++itr) {
-                res = std::move(res) + itr->x() * (std::next(itr)->y() - std::prev(itr)->y());
+            auto res = itr0->x() * itr1->y() - last->x() * std::prev(last)->y();
+            for (; itr2 != end; ++itr2, ++itr1, ++itr0) {
+                res = std::move(res) + itr1->x() * (itr2->y() - itr0->y());
             }
             return res;
         }

diff --git a/include/recti/rpolygon.hpp b/include/recti/rpolygon.hpp
@@ -54,12 +54,11 @@ namespace recti {
          */
         constexpr auto signed_area() const -> T {
             assert(this->_vecs.size() >= 1);
-            auto first = this->_vecs.begin();
-            auto res = first->x() * first->y();
-            auto itr0 = first;
-            for (auto itr = std::next(first); itr != this->_vecs.end(); ++itr) {
-                res = std::move(res) + itr->x() * (itr->y() - itr0->y());
-                itr0 = itr;
+            auto itr1 = this->_vecs.begin();
+            auto itr0 = itr1++;
+            auto res = itr0->x() * itr0->y();
+            for (; itr1 != this->_vecs.end(); ++itr1, ++itr0) {
+                res = std::move(res) + itr1->x() * (itr1->y() - itr0->y());
             }
             return res;
             // return std::accumulate(++first, this->_vecs.end(), std::move(res),