StackOverflow2013

Note that there are some explanatory texts on larger screens.

plurals

POc++ global variable out of scope in class
text
Body
copied!<p>So I'm trying to write a basic red black tree in c++. This is my first real transition from C to C++ and I'm running into a scope issue. I'm trying to use a global variable to keep track of the root of the tree because I'm lazy and don't want to have every function pass the old or new root back. Anyways, I have the pointer (named root) declared outside of any function or class and in my mind, should be visible to anyone. When I compile, I get:</p> <pre><code>main.cpp: In member function ‘void node::ins(int)’: main.cpp:23:4: error: ‘root’ was not declared in this scope main.cpp: In member function ‘void node::case3()’: main.cpp:110:4: error: ‘root’ was not declared in this scope </code></pre> <p>So, the functions inside the class can't see the global variable but the main function can. What do I have to do to let the functions inside the class see this variable? Thanks in advance. Max</p> <pre><code>#include <iostream> #include <cstdio> using namespace std; const int BLACK = 0; const int RED = 1; class node{ public: node *parent = NULL; node *left = NULL; node *right = NULL; int color = RED; int num = -1; int isRoot(void){ if(parent == NULL) return 1; else return 0; }; void ins(int newNum){ if(isRoot() && num == -1){//if first insertion num = newNum; color = BLACK; root = this; }else if(newNum < num) if(left == NULL){ left = new node; left->parent = this; left->num = newNum; left->fixColor(); }else left->ins(newNum); else if(right == NULL){ right = new node; right->parent = this; right->num = newNum; right->fixColor(); }else right->ins(newNum); }; int uncleColor(void){ if(parent != NULL){ if(parent->parent != NULL){ node *grandparent = parent->parent; if(grandparent->left == parent) if(grandparent->right == NULL) return BLACK; else return grandparent->right->color; else{ if(grandparent->left == NULL) return BLACK; else return grandparent->left->color; } }else cout << "[Error] Grandparent DNE, at root\n"; }else cout << "[Error] Parent DNE, at root\n"; return -1; }; void fixColor(void){ if(isRoot()){ color = BLACK; }else if(color == RED){ if(parent->color == RED){//if parent is black, nothing violated int uncle = uncleColor(); if(uncle == RED){//uncle is red too case1(); parent->parent->fixColor();//call recursivly on grandparent }else if(uncle == BLACK){//uncle is black case2();//case 2 will then call case 3 }else cout << "[Error] fixColor uncle color mismatch\n"; } }else cout << "[Error] fixcolor node is black?\n"; }; void case1(void){ node *grandparent = parent->parent; node *uncle = NULL; if(grandparent->left == parent) uncle = grandparent->right; else uncle = grandparent->left; uncle->color = BLACK; parent->color = BLACK; grandparent->color = RED; }; void case2(void){ node *grandparent = parent->parent; if(this == parent->right && parent == grandparent->left){ rotate_left(); left->case3(); }else if(this == parent->left && parent == grandparent->right){ rotate_right(); right->case3(); }else case3(); }; void case3(void){ node *grandparent = parent->parent; parent->color = BLACK; color = RED; if(this == parent->left) grandparent->rotate_right(); else grandparent->rotate_left(); if(parent->isRoot()) root = parent; }; void rotate_left(void){ node *grandparent = parent->parent; grandparent->left = this; parent->right = this->left; this->left = parent; parent->parent = this; parent = grandparent; }; void rotate_right(void){ node *grandparent = parent->parent; grandparent->right = this; parent->left = this->right; this->right = parent; parent->parent = this; parent = grandparent; }; void del(int val){ }; }; node *root = NULL; int main(int argc, char **argv){ root = new node; char READ_task; int READ_val; FILE *txtPtr = NULL; if((txtPtr = fopen(argv[1],"r")) == NULL){printf("[Error] Unable to Load File: '%s'\nExiting...\n",argv[1]);} else{ while(fscanf(txtPtr, "%c%d", &READ_task, &READ_val) == 2){ if(READ_task == 'i') root->ins(READ_val); else if(READ_task == 'd') root->del(READ_val); else cout << "Instruction from file not i or d\n"; } } return 0; } </code></pre>

Querying!

Guidance

An individual column

Larger individual text columns get their own page to allow for proper reading.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload