Avoid to_remove vector in select helper function

Remove the need to allocate anything when removing selections.

src/normal.cc

@@ -92,14 +92,16 @@ void select(Context& context, T func)
     }
     else
     {
-        Vector<int> to_remove;
-        for (int i = 0; i < (int)selections.size(); ++i)
+        auto main_index = selections.main_index();
+        auto new_end = selections.begin();
+        for (size_t i = 0; i < selections.size(); ++i)
         {
             auto& sel = selections[i];
             auto res = func(context, sel);
             if (not res)
             {
-                to_remove.push_back(i);
+                if (i <= main_index and main_index != 0)
+                    --main_index;
                 continue;
             }
 
@@ -112,12 +114,13 @@ void select(Context& context, T func)
             }
             if (not res->captures().empty())
                 sel.captures() = std::move(res->captures());
+            *new_end++ = std::move(sel);
         }
-
-        if (to_remove.size() == selections.size())
+        if (new_end == selections.begin())
             throw no_selections_remaining{};
-        for (auto& i : to_remove | reverse())
-            selections.remove(i);
+
+        selections.set_main_index(main_index);
+        selections.remove_from(new_end - selections.begin());
     }
 
     selections.sort_and_merge_overlapping();

src/selection.cc

@@ -33,6 +33,15 @@ void SelectionList::remove(size_t index)
     if (index < m_main or m_main == m_selections.size())
         --m_main;
 }
+
+void SelectionList::remove_from(size_t index)
+{
+    kak_assert(index > 0);
+    m_selections.erase(begin() + index, end());
+    if (index <= m_main)
+        m_main = m_selections.size() - 1;
+}
+
 void SelectionList::set(Vector<Selection> list, size_t main)
 {
     kak_assert(main < list.size());

src/selection.hh

@@ -125,6 +125,7 @@ struct SelectionList
     const_iterator end() const { return m_selections.end(); }
 
     void remove(size_t index);
+    void remove_from(size_t index);
 
     const Selection* data() const { return m_selections.data(); }
     size_t size() const { return m_selections.size(); }