Fix the nullptr warning in red/black tree impl.

Author: layus

vm/vm/main/dictionary-decl.hh

@@ -42,14 +42,6 @@ private:
   enum Color { clBlack, clRed };
 
   struct Node {
-    bool safeIsBlack() {
-      return (this == nullptr) || (color == clBlack);
-    }
-
-    bool safeIsRed() {
-      return (this != nullptr) && (color == clRed);
-    }
-
     Node* getOneChild() {
       if (left == nullptr) {
         return right;
@@ -183,6 +175,14 @@ private:
   inline
   void rotateRight(Node* parent, Node* child);
 
+  bool isBlack(Node* n) {
+    return (n == nullptr) || (n->color == clBlack);
+  }
+
+  bool isRed(Node* n) {
+    return (n != nullptr) && (n->color == clRed);
+  }
+
 private:
   Node* root;
 };

vm/vm/main/dictionary.hh

@@ -179,7 +179,7 @@ void NodeDictionary::fixInsert(VM vm, Node* node) {
 
     Node* uncle = grandParent->getTheOtherChild(parent);
 
-    if (uncle->safeIsRed()) {
+    if (isRed(uncle)) {
       // Case 3
       parent->color = clBlack;
       uncle->color = clBlack;
@@ -265,7 +265,7 @@ void NodeDictionary::fixRemove(VM vm, Node* node, Node* parent) {
     Node* siblingLeft = sibling->left;
     Node* siblingRight = sibling->right;
 
-    if (siblingLeft->safeIsBlack() && siblingRight->safeIsBlack()) {
+    if (isBlack(siblingLeft) && isBlack(siblingRight)) {
       if (parent->color == clBlack) {
         // Case 3
         sibling->color = clRed;
@@ -277,12 +277,12 @@ void NodeDictionary::fixRemove(VM vm, Node* node, Node* parent) {
       }
     } else {
       // Case 5
-      if ((node == parent->left) && siblingRight->safeIsBlack()) {
-        assert(siblingLeft->safeIsRed());
+      if ((node == parent->left) && isBlack(siblingRight)) {
+        assert(isRed(siblingLeft));
         rotateRight(sibling, siblingLeft);
         std::swap(sibling, siblingLeft);
-      } else if ((node == parent->right) && siblingLeft->safeIsBlack()) {
-        assert(siblingRight->safeIsRed());
+      } else if ((node == parent->right) && isBlack(siblingLeft)) {
+        assert(isRed(siblingRight));
         rotateLeft(sibling, siblingRight);
         std::swap(sibling, siblingRight);
       }