Merge pull request #1457 from AThousandShips/foreach_list

[Core] Reduce and prevent unnecessary random-access to `List`

Author: dsnopek

include/godot_cpp/templates/list.hpp

@@ -139,54 +139,58 @@ class List {
 
 	typedef T ValueType;
 
-	struct Iterator {
-		_FORCE_INLINE_ T &operator*() const {
+	struct ConstIterator {
+		_FORCE_INLINE_ const T &operator*() const {
 			return E->get();
 		}
-		_FORCE_INLINE_ T *operator->() const { return &E->get(); }
-		_FORCE_INLINE_ Iterator &operator++() {
+		_FORCE_INLINE_ const T *operator->() const { return &E->get(); }
+		_FORCE_INLINE_ ConstIterator &operator++() {
 			E = E->next();
 			return *this;
 		}
-		_FORCE_INLINE_ Iterator &operator--() {
+		_FORCE_INLINE_ ConstIterator &operator--() {
 			E = E->prev();
 			return *this;
 		}
 
-		_FORCE_INLINE_ bool operator==(const Iterator &b) const { return E == b.E; }
-		_FORCE_INLINE_ bool operator!=(const Iterator &b) const { return E != b.E; }
+		_FORCE_INLINE_ bool operator==(const ConstIterator &b) const { return E == b.E; }
+		_FORCE_INLINE_ bool operator!=(const ConstIterator &b) const { return E != b.E; }
 
-		Iterator(Element *p_E) { E = p_E; }
-		Iterator() {}
-		Iterator(const Iterator &p_it) { E = p_it.E; }
+		_FORCE_INLINE_ ConstIterator(const Element *p_E) { E = p_E; }
+		_FORCE_INLINE_ ConstIterator() {}
+		_FORCE_INLINE_ ConstIterator(const ConstIterator &p_it) { E = p_it.E; }
 
 	private:
-		Element *E = nullptr;
+		const Element *E = nullptr;
 	};
 
-	struct ConstIterator {
-		_FORCE_INLINE_ const T &operator*() const {
+	struct Iterator {
+		_FORCE_INLINE_ T &operator*() const {
 			return E->get();
 		}
-		_FORCE_INLINE_ const T *operator->() const { return &E->get(); }
-		_FORCE_INLINE_ ConstIterator &operator++() {
+		_FORCE_INLINE_ T *operator->() const { return &E->get(); }
+		_FORCE_INLINE_ Iterator &operator++() {
 			E = E->next();
 			return *this;
 		}
-		_FORCE_INLINE_ ConstIterator &operator--() {
+		_FORCE_INLINE_ Iterator &operator--() {
 			E = E->prev();
 			return *this;
 		}
 
-		_FORCE_INLINE_ bool operator==(const ConstIterator &b) const { return E == b.E; }
-		_FORCE_INLINE_ bool operator!=(const ConstIterator &b) const { return E != b.E; }
+		_FORCE_INLINE_ bool operator==(const Iterator &b) const { return E == b.E; }
+		_FORCE_INLINE_ bool operator!=(const Iterator &b) const { return E != b.E; }
 
-		_FORCE_INLINE_ ConstIterator(const Element *p_E) { E = p_E; }
-		_FORCE_INLINE_ ConstIterator() {}
-		_FORCE_INLINE_ ConstIterator(const ConstIterator &p_it) { E = p_it.E; }
+		Iterator(Element *p_E) { E = p_E; }
+		Iterator() {}
+		Iterator(const Iterator &p_it) { E = p_it.E; }
+
+		operator ConstIterator() const {
+			return ConstIterator(E);
+		}
 
 	private:
-		const Element *E = nullptr;
+		Element *E = nullptr;
 	};
 
 	_FORCE_INLINE_ Iterator begin() {
@@ -519,7 +523,14 @@ class List {
 		}
 	}
 
-	T &operator[](int p_index) {
+	// Index operator, kept for compatibility.
+	_FORCE_INLINE_ T &operator[](int p_index) {
+		return get(p_index);
+	}
+
+	// Random access to elements, use with care,
+	// do not use for iteration.
+	T &get(int p_index) {
 		CRASH_BAD_INDEX(p_index, size());
 
 		Element *I = front();
@@ -532,7 +543,14 @@ class List {
 		return I->get();
 	}
 
-	const T &operator[](int p_index) const {
+	// Index operator, kept for compatibility.
+	_FORCE_INLINE_ const T &operator[](int p_index) const {
+		return get(p_index);
+	}
+
+	// Random access to elements, use with care,
+	// do not use for iteration.
+	const T &get(int p_index) const {
 		CRASH_BAD_INDEX(p_index, size());
 
 		const Element *I = front();