What Does Expression: cannot dereference end list iterator mean? - c++

I keep getting this error message on my code, its saying its on line 149, but there's nothing on line 149 and so I'm having trouble understanding what is wrong. Does anyone know?
Context - this is a simple balancing symbols checker program exercise
This is the error message after i type in the name of the file.
This is the full code:
#include <iostream>
#include <fstream>
#include <string>
#include<list>
using namespace std;
void openInputFile(ifstream& inFile);
template<class T>
class Stack {
list <T> data;
public:
Stack() : data() {}
void push(T newItem) { data.push_front(newItem); }
T pop() { T topVal = top(); data.pop_front();
return topVal; }
T top() const { return *data.begin(); }
bool isEmpty() const { return data.size() == 0; }
int size() const { return data.size(); }
void clear() { data.clear(); }
};
class brackets {
brackets() : bracket() {}
char bracket;
};
int main()
{
Stack<char> dataChecker;
ifstream inFile;
string charChecker;
char currChar;
int size;
bool goodToGo = true;
cout << "First enter the name of the data file,
then press enter. " << endl;
openInputFile(inFile);
while (getline(inFile, charChecker)) {
size = charChecker.size();
if (charChecker.find("begin") ||
charChecker.find("Begin") ||
charChecker.find("BEGIN")) {
dataChecker.push('b');
}
if (charChecker.find("end") ||
charChecker.find("End") ||
charChecker.find("END")) {
currChar = dataChecker.pop();
if (currChar != 'b') {
goodToGo = false;
break;
}
}
for (int i = 0; i < size; i+= 1) {
if ((charChecker[i] == '{') ||
(charChecker[i] == '}') ||
(charChecker[i] == '[') ||
(charChecker[i] == ']') ||
(charChecker[i] == '(') ||
(charChecker[i] == ')')) {
switch (charChecker[i]) {
case '{' :
dataChecker.push('{');
case '[':
dataChecker.push('[');
case '(':
dataChecker.push('(');
case '}':
currChar = dataChecker.pop();
if (currChar != '{') {
goodToGo = false;
break;
}
case ']':
currChar = dataChecker.pop();
if (currChar != '[') {
goodToGo = false;
break;
}
case ')':
currChar = dataChecker.pop();
if (currChar != '(') {
goodToGo = false;
break;
}
}
}
}
}
if (goodToGo == false) {
cout << "There is an error in the data." <<
endl;
}
else {
cout << "The data looks good!" << endl;
}
return 0;
}
void openInputFile(ifstream& inFile) {
cout << "Please enter a filename: ";
string filename;
cin >> filename;
inFile.open(filename);
while (!inFile) {
cout << "Bad file name";
cout << "Please enter a filename: ";
cin >> filename;
inFile.clear();
inFile.open(filename);
}
}

Looking into line 149 of file <list> (the dialog message gives you the full path, also right-click and open on #include <list> in the editor helps):
_NODISCARD reference operator*() const {
#if _ITERATOR_DEBUG_LEVEL == 2
const auto _Mycont = static_cast<const _Mylist*>(this->_Getcont());
_STL_ASSERT(_Mycont, "cannot dereference value-initialized list iterator");
_STL_VERIFY(this->_Ptr != _Mycont->_Myhead, "cannot dereference end list iterator");
#endif // _ITERATOR_DEBUG_LEVEL == 2
return this->_Ptr->_Myval;
}
So this is simple. You have a list iterator (for example iter) and call operator* on it (-> *iter). That is not allowed and the assertion is telling you that. When you run the program in a debugger and look at the call stack you can directly navigate to the code where you call *iter.
Maybe you are calling top or pop on an empty Stack?

Related

infix to postfix program not producing the correct output

#include <iostream>
#include <string>
#include <vector>
#include <sstream>
#include <iomanip>
using namespace std;
class Stack {
public:
string stack[100][1];
int size;
Stack() { size = 0; }
~Stack() {};
void push(string data) {
stack[size][0] = data;
size += 1;
}
bool empty() {
if (size == 0)
{
return true;
}
else
{
return false;
}
}
string pop() {
size -= 1;
return stack[size][0];
}
string top() {
if (empty())
cout << "Stack is empty";
return stack[size - 1][0];
}
};
int pre(char op)
{
switch (op)
{
case '(': case ')': return 0;
case '+': case '-': return 1;
case '*': case '/': return 2;
}
return -1;
}
vector<string> infix_to_postfix(const vector<string>& expr) {
vector<string> postfix;
string op;
Stack st;
for (int i = 0; i < expr.size(); i++) {
if (expr[i][0] == '+' || expr[i][0] == '-' || expr[i][0] == '*' || expr[i][0] == '/') {
while (!st.empty()) {
op = (st.top()[0]);
if (pre(expr[i][0]) <= pre(op[0]))
postfix.push_back(st.pop());
else break;
}
postfix.push_back(expr[i]);
}
else if (expr[i][0] == '(') {
st.push(expr[i]);
}
else if (expr[i][0] == ')') {
while (!st.empty()) {
op = st.pop();
if (op[0] == '(') break;
else {
postfix.push_back(op);
}
}
}
else {
postfix.push_back(expr[i]);
}
}
return postfix;
}
int main() {
auto expr = infix_to_postfix({ "(", "2", "+", "3", ")", "*", "7" });
for (auto& elem : expr)
{
std::cout << elem << ", ";
}
std::cout << "\n";
return 0;
}
This program is supposed to convert from infix to postfix but it is not producing the correct output. I'm expecting the output to be:
2, 3, +, 7, *,
but the output is
2, +, 3, *, 7,
You have two issues.
When handling an operator, after popping the lower precedence operators you need to push the new operator onto the stack rather than adding it to the result:
if (expr[i][0] == '+' || expr[i][0] == '-' || expr[i][0] == '*' || expr[i][0] == '/') {
while (!st.empty()) {
op = (st.top()[0]);
if (pre(expr[i][0]) <= pre(op[0]))
postfix.push_back(st.pop());
else break;
}
st.push(expr[i]);
}
At the end of the function you need to pop any remaining operators off the stack:
while (!st.empty())
{
postfix.push_back(st.pop());
}
return postfix;

balances brackets problem(always the output is good)

I have to write a program which balances a string with brackets.I wrote the program but it doesn't matter which string I enter because the program always says that the string is good.
Here's the code:
header file
#ifndef HEADER_H_
#define HEADER_H_
#include <string>
struct Element {
char data;
Element* link;
};
typedef Element* Stack;
void initStack(Stack& S);
void push(Stack& S, int a);
void pop(Stack &S);
int top(Stack& S);
bool isEmpty(Stack &S);
bool goodPair(char deschis, char inchis);
bool check(std::string s);
#endif
functions file
#include <iostream>
#include <string>
#include "header.h"
using namespace std;
void initStack(Stack& S)
{
S = nullptr;
}
void push(Stack& S, int a)
{
Element*nou = new Element;
nou->data = a;
nou->link = S;
S = nou;
}
void pop(Stack& S)
{
Stack aux = S;
S = S->link;
delete(aux);
}
int top(Stack& S)
{
if (isEmpty(S))
return int();
return S->data;
}
bool isEmpty(Stack &S)
{
if (S == 0)
return true;
else
return false;
}
bool goodPair(char deschis, char inchis)
{
if (deschis == '(' && inchis == ')')
return true;
else if (deschis == '[' && inchis == ']')
return true;
else if (deschis == '{' && inchis == '}')
return true;
else if (deschis == '<' && inchis == '>')
return true;
else
return false;
}
bool check(std::string s)
{
Element* S;
for (int i = 0; i < s.length(); i++)
{
if (s[i] == '(' || s[i] == '[' || s[i] == '{' || s[i] == '<')
push(S, s[i]);
else
{
if (s[i] == ')' || s[i] == ']' || s[i] == '}' || s[i] == '>')
if (isEmpty(S) || !goodPair(top(S), s[i]))
return false;
else
pop(S);
}
}
if (isEmpty(S))
return false;
else
return true;
}
main file
#include <iostream>
#include <string>
#include "header.h"
using namespace std;
int main()
{
Stack S;
initStack(S);
string s;
cout << "Write the string:";
cin >> s;
if (check(s))
cout << "Good";
else
cout << "Bad";
return 0;
}
I used a stack and I traversed each character.If the character is an opening bracket I put it in the stack.When the character is a closing bracket, I compare it with the top of the stack.If it's good I pop the top of the stack.
You create a pointer to Element (aliased as Stack) S in main() and initialize it with nullptr using initStack() and then you do not use this variable anymore. Instead you create a local S in function check() and use it uninialized, which leads to UB.
Looks like you get confused by naming as you call of them S (variable in main(), variable in check(), all reference parameters all called S). It is not illegal to do so, but looks like you confused yourself. (you even called std::string lowercase s to increase confusion)
Also you have logical error in your function:
if (isEmpty(S))
return false;
else
return true;
should be opposite, if stack is empty then string is balanced, not vice versa. So replace it with:
return isEmpty( S );

Infix/Postfix evaluator terminating issue

I've got a few different functions that on their own work fine. Now I am trying to put them together into one file. My debugger is throwing segmentation faults in the infixToPostfix function.
When I watch the ns variable, it does not show anything getting assigned to it, but it prints out the postfix expression when I actually run the code. When ns passes into PostfixEvaulation, it runs to the top member function of TemplateStack and crashes with:
terminate called after throwing an instance of "std::string"
This only happens when I pass a string with an operator. When I pass a string of just numbers, everything runs fine,
but it still does not seem to call PostfixEvaluation.
#include <iostream>
#include <sstream>
#include <string>
#include <typeinfo>
using namespace std;
//Class Template Stack declaration
template <class T>
class TemplateStack {
public:
typedef T type;
TemplateStack()
{
max_size_ = 50;
TopOfStack = 0;
data_ = new T[max_size_];
} //Default Constructor taking no parameters
void push(T element)
{
if (TopOfStack == max_size_)
throw string("Stack's underlying storage is overflow");
TopOfStack++;
data_[TopOfStack] = element;
}
void pop() {
if (TopOfStack == -1)
throw string("Stack is empty");
TopOfStack--;
}
T top() {
if (TopOfStack == -1)
throw string("Stack is empty");
return data_[TopOfStack];
}
private:
int TopOfStack; //Generic data type for the top element of stack
size_t max_size_;
T* data_;
};
//Function to Evauluate the Postfix notation expresion
int PostfixEvaulation(string input){
//string input;
int operand1, operand2, result,number;
TemplateStack<char>operation;
stringstream temp;
int i=0;
while (i < input.length())
{
if (isdigit(input[i]))
{
operation.push(input[i]);
}
else
{
operand2 = operation.top();
temp << operation.top();
operation.pop();
operand1 = operation.top();
temp << operation.top();
operation.pop();
switch(operand1,operand2)
{
case '+': result=operand1 + operand2;
break;
case '-': result=operand1 - operand2;
break;
case '*': result=operand1 * operand2;
break;
case '/': result=operand1 / operand2;
break;
}
operation.push(result);
}
i++;
}
cout << "The result is: "<<temp.str()<<endl;
//cin.ignore(numeric_limits<streamsize>::max(), '\n');
return 0;
}
//Function to return precedence of operators
int prec(char c)
{
if(c == '^')
return 3;
else if(c == '*' || c == '/')
return 2;
else if(c == '+' || c == '-')
return 1;
else
return -1;
}
//Function: Convert Infix to Postfix
void infixToPostfix(string s)
{
TemplateStack<char> st;
st.push('N');
int l = s.length();
string ns;
for (int i = 0; i < l; i++) {
// If the scanned character is an operand, add it to output string.
if ((s[i] >= 'a' && s[i] <= 'z') || (s[i] >= 'A' && s[i] <= 'Z')) {
ns += s[i];
}
// If the scanned character is an ‘(‘, push it to the stack.
else if (s[i] == '(') {
st.push('(');
}
// If the scanned character is an ‘)’, pop and to output string from the stack
// until an ‘(‘ is encountered.
else if (s[i] == ')') {
while (st.top() != 'N' && st.top() != '(') {
char c = st.top();
st.pop();
ns += c;
}
if (st.top() == '(') {
char c = st.top();
st.pop();
}
}
//If an operator is scanned
else {
while (st.top() != 'N' && prec(s[i]) <= prec(st.top())) {
char c = st.top();
st.pop();
ns += c;
}
st.push(s[i]);
}
}
//Pop all the remaining elements from the stack
while (st.top() != 'N') {
char c = st.top();
st.pop();
ns += c;
}
cout << "Here is the ns variable: "<< ns << endl;
PostfixEvaulation(ns);//Call the PostFixEvaluationFunction with the ns (postfix notation) variab
}
//Function: User inputs Expression
void GetInput(){
string input;
cout << "Enter Infix Expression: ";
getline(cin, input);
infixToPostfix(input);
}
int main()
{
GetInput();
}

C++ Infix to Postfix program, Stack is continuously empty?

I'm working on a program for a computer science class. I have everything completed and separated into the interface/implementation and for some reason, the program loops infinitely and says "Stack is empty!" after the peek() function is called.
I've tried inserting cout << statements to see if I can pinpoint the issue, however, no luck. I would appreciate it if someone else could take a look at it.
Thank You
Header
#ifndef STACK_H
#define STACK_H
/////////////////////////////////////////////////////
////Includes/////////////////////////////////////////
/////////////////////////////////////////////////////
#include <iostream>
#include <fstream>
#include <cstdlib>
#include <stdlib.h>
#include <iomanip>
#include <sstream>
#include <stdio.h>
/////////////////////////////////////////////////////
using namespace std;
/*-------------------------------------------------------------------------------------------------------------*/
template <typename Object>
class Stack
{
private:
class stackListNode
{
public:
Object data;
stackListNode *next;
private:
//Nothing to declare-->placeholder since class
//sets data members to private initially
};
stackListNode *top;
public:
/////////////////////////////////////////////////
//Constructor Function//////////////////////////
Stack() {top = NULL;}
/////////////////////////////////////////////////
//Rest of functions defined inline for simplicity
void push(char token) // Push token onto the stack and create new node for top of stack
{
stackListNode *newNode = new stackListNode;
newNode->data = token;
newNode->next = top;
top = newNode;
}
int pop()
{
if(empty())
{
cout << "Stack is empty!\n" << endl;
return NULL;
}
stackListNode *temp = top;
top = temp->next;
}
char peek()
{
if(empty())
{
cout << "Stack is empty!\n" << endl;
return NULL;
}
return top->data;
}
int empty()
{
return top == NULL;
}
};
#endif
Main File:
/////////////////////////////////////////////////////
////Includes/////////////////////////////////////////
/////////////////////////////////////////////////////
#include <iostream>
#include <fstream>
#include <string>
#include "Stack.h"
/////////////////////////////////////////////////////
using namespace std;
int precendence(char stack_beginning); //ensures order of operations.
int precendence(char*myArray);
void InFixToPostfix(ifstream& in_file);
double EvaluatePostfix(double first_operand, double second_operand, char*myArray);
int main()
{
////VARS/////////////////////////////////////////////
string absolutePath;
cout << endl;
cout << "Please type in the name of the file you would to open \n";
cin >> absolutePath;
ifstream in_file;
in_file.open(absolutePath.c_str());
if(!in_file)
{
cout << "failed to open input file\n" ;
return 1 ;
}
else
{
InFixToPostfix(in_file); //kicks off program
}
}
void InFixToPostfix(ifstream& in_file)
{
string infix;
int right_parentheses =0;
int left_parentheses =0;
while(getline(in_file, infix))
{
char myArray[infix.size()];
strcpy(myArray, infix.c_str());
for(int i = 0; i < sizeof(myArray); i++)
{
if(myArray[i] == '(')
{
right_parentheses++;
}
if(myArray[i] == ')')
{
left_parentheses++;
}
}
if(right_parentheses!=left_parentheses)
{
cout << endl;
cout << "There is a typo in one of the expressions in your file \n";
cout << "Please fix it and rerun the program \n";
exit(1);
}
for(int i = 0; i < sizeof(myArray); i++)
{
//int number = int(myArray[i]);
//deferences the pointer and reads each char in the array
//as an int rather than a character.
//int number = myArray[i];
if(isxdigit(myArray[i]) > 0) //function used to check for hexidecimal values (i.e. int's)
{
goto exit_out;
}
else if(myArray[i] == '(' || myArray[i] == ')' || myArray[i] == '+' || myArray[i] == '-' || myArray[i] == '*' || myArray[i] == '/' || myArray[i] == '\\' || myArray[i] == '\n')
{
goto exit_out;
}
else if(myArray[i] == char(32)) //checks to see if there is a space
{
goto exit_out;
}
else
{
cout << endl;
cout << "There is an invalid character in the file\n";
exit(1);
}
exit_out:;
}
////////Declares a STRING Stack////////////////////////////////
Stack<char> stack_string;
////////Declares an Int Stack/////////////////////////////////
Stack<int> stack_int;
//////////////////////////////////////////////////////////////
for(int i = 0; i < sizeof(myArray); i++)
{
int number = isxdigit(myArray[i]);
if(number > 0)
{
cout << number;
//outputs the number b/c it is an operand
}
if(myArray[i] == '(')
{
stack_string.push(myArray[i]);
}
if(myArray[i] == ')')
{
//cout << "test";
while(stack_string.peek() != '(')
{
cout << stack_string.peek();
stack_string.pop(); //pops to the peek
}
stack_string.pop(); // if there is a ), pops to the peek
}
if(myArray[i] == '+' || myArray[i] == '-' || myArray[i] == '/' || myArray[i] == '*')
{
if(stack_string.empty())
{
stack_string.push(myArray[i]); //if there's nothing on the stack, pushes the current character
//goto done;
break; //breaks out of the statement
}
char stack_beginning = stack_string.peek();
int stack_top = precendence(stack_beginning);
//int stack_top = precendence(stack_string.peek());
int operatorHierarchy = precendence(myArray);
//must be declared here because i will have been interated through array
if(operatorHierarchy > stack_top)
{
stack_string.push(myArray[i]);
}
else if(operatorHierarchy <= stack_top) //could also be an if
{
dump_out:;
cout << stack_string.peek();
stack_string.pop();
int rerunThroughStack =0;
char new_stack_beginning = stack_string.peek();
rerunThroughStack = precendence(new_stack_beginning);
if(operatorHierarchy < stack_top)
{
stack_string.push(myArray[i]);
goto done; //could break
}
if(stack_string.peek() == '(')
{
stack_string.push(myArray[i]);
goto done;
}
if(stack_string.empty())
{
stack_string.push(myArray[i]);
goto done;
}
goto dump_out;
}
}
done:;
}
cout << stack_string.peek() << endl;
//////////Evaluate Section/////////////////////////////
for(int i = 0; i < sizeof(myArray); i++)
{
if(isxdigit(myArray[i]) > 0) //this is a number
{
stack_int.push(isxdigit(myArray[i]));
goto end;
}
else if(myArray[i] == '*' || myArray[i] == '+' || myArray[i] == '-' || myArray[i] == '/')
{
double first_operand;
first_operand = stack_int.peek(); //fetches first operand on the stack_int
stack_int.pop();
//////////////////
double second_operand;
second_operand = stack_int.peek();
stack_int.pop();
//////////////////
double answer;
answer = EvaluatePostfix(first_operand, second_operand, myArray); //THIS PROBABLY IS NOT RIGHT
stack_int.push(answer);
}
end:;
}
/*
int size_of_stack;
size_of_stack = stack_int.size();
if(size_of_stack == 1)
{
cout << stack_int.peek();
}
*/
}
}
double EvaluatePostfix(double first_operand, double second_operand, char* myArray) //might have to pass array as reference
{
/*
Cycle through the characters passed in through myArray[i];
*/
for(int i = 0; i < sizeof(myArray); i++)
{
if(myArray[i] == '*')
{
double first_answer;
first_answer = (second_operand * first_operand);
return first_answer;
}
else if(myArray[i] == '/')
{
double second_answer;
second_answer = (second_operand / first_operand);
return second_answer;
}
else if(myArray[i] == '+')
{
double third_answer;
third_answer = (second_operand + first_operand);
return third_answer;
}
else if(myArray[i] == '-')
{
double fourth_answer;
fourth_answer = (second_operand - first_operand);
return fourth_answer;
}
/*
else
{
cout << "There must be an error in your file" <<endl;
break;
exit(1);
}
*/
}
}
int precendence(char stack_beginning)
{
int precendence;
if(stack_beginning == '*' || stack_beginning == '/')
{
precendence = 2;
return precendence;
}
//by making it 2, the precendence is dubbed less than +/-
if(stack_beginning == '+' || stack_beginning == '-')
{
precendence = 1;
return precendence;
}
} //by making it 1, the precendence is dubbed greater than */"/"
int precendence(char*myArray)
{
int precendence;
for(int i = 0; i < sizeof(myArray); i++)
{
if(myArray[i] == '*' || myArray[i] == '/')
{
precendence = 2;
return precendence;
}
//by making it 2, the precendence is dubbed less than +/-
if(myArray[i] == '+' || myArray[i] == '-')
{
precendence = 1;
return precendence;
}
} //by making it 1, the precendence is dubbed greater than */"/"
}

Infix to Postfix calculator, implement sin cos and X&Y variables?

I'm pretty green at C++, and I have to make an infix to postfix calculator that supports sin() and cos(), and it has to be a 2 variable function, something like z=3x*sin(3+4y), I already got the parser from infix to postfix, but I don't know how to implement sin and cos, I've been told that I could set them as operator, like +, -, /, etc. and to set a specific token for them, like "s" for sin() and "c" for cos() but I don't exactly know how, and I don't know either how to implement the variables x & y, I know that this is not something I should be asking, but I'm just tired and desperate.
Here's the code I have. I'm using Ubuntu 11:
#include <iostream>
#include <cmath>
#include <cstdlib>
#include <string>
#define MAX_SIZE 20
using namespace std;
template<class T> class Stack
{
private:
T item[MAX_SIZE];
int top;
public:
Stack()
{
top = -1;
}
void push(T data)
{
if(!this->is_full())
item[++top] = data;
else
{
cout << "Stack Error" << endl;
exit(10);
}
}
T pop()
{
if(!this->is_empty())
{
return item[top--];
}
else
{
cout << "Stack is Empty" << endl;
exit(11);
}
}
int size()
{
return top + 1;
}
bool is_empty()
{
if(top == -1)
return true;
else
return false;
}
bool is_full()
{
if(top == MAX_SIZE - 1)
return true;
else
return false;
}
void display()
{
for(int i = 0; i < this->size(); i++)
{
cout << item[i] << " ";
}
cout << endl;
}
T return_top()
{
return item[top];
}
};
class Convert
{
private:
bool num_flag;
bool two_digit_flag;
public:
Convert();
string return_with_bracket(string infix);
void to_Postfix(string infix,char postfix[]);
bool prcd(char op1, char op2);
int isOperand(char op);
int isOperator(char op);
bool return_flag()
{
return num_flag;
}
};
Convert::Convert()
{
this->num_flag = false;
this->two_digit_flag = false;
}
string Convert::return_with_bracket(string infix)
{
return("(" + infix + ")");
}
bool Convert::prcd(char op1, char op2)
{
if((op1 == '+' || op1 == '-' || op1 == '*' || op1 == '/') && op2 == '(')
return true;
if(op1=='+' && op2=='+')
return true;
if(op1=='-' && op2=='-')
return false;
if(op1=='-' && op2=='+')
return false;
if(op1=='+' && op2=='-')
return false;
if(op1=='/' && op2=='/')
return false;
if(op1=='/' && (op2=='-' || op2=='+'))
return true;
if(op1=='*' && (op2=='+' || op2=='-'))
return true;
if((op1 == '-' || op1 == '+') && (op2 =='*' || op2 == '/'))
return false;
if((op1 == '$' || op1 == '+') && (op2 =='*' || op2 == '/' || op2=='-'))
return true;
if((op1 == '-' || op1 == '+' || op1 =='*' || op1 == '/')&& op2=='^')
return false;
if(op1 == '^' && ( op2 == '+' || op2 =='*' || op2 == '/' || op2=='-'))
return false;
}
int Convert::isOperand(char op)
{
return(op >= '0' && op <= '9');
}
int Convert::isOperator(char op)
{
return(op =='+' || op =='-' || op == '/' || op =='*' || op =='^');
}
void Convert::to_Postfix(string infix, char postfix[])
{
int position, outpos=0;
char c;
int count = 0;
char temp;
char stacktop;
Stack<char> stack;
for(position = 0; (c = infix[position]) != '\0'; position++)
{
if(this->isOperand(c))
{
postfix[outpos++] = c;
this->num_flag = true;
count++;
if(count >= 2)
{
this->two_digit_flag = true;
}
}
else if(this->isOperator(c))
{
count = 0;
if(isOperator(infix[position]) && isOperator(infix[position + 1]))
{
cout << " '\' aMissing argument in between " << infix[position] << " and " << infix[position + 1] << " in column " << position + 1 << endl;
exit(9);
}
if(this->prcd(c, stacktop))
{
stacktop = stack.return_top();
stack.push(c);
stacktop = c;
}
else
{
while(true)
{
temp = stack.pop();
postfix[outpos++] = temp;
stacktop = stack.return_top();
if(prcd(c, stacktop) || stacktop == '(')
break;
}
stack.push(c);
stacktop = stack.return_top();
}
}
else if(c == '(')
{
count = 0;
stack.push(c);
stacktop = stack.return_top();
}
else if(c == ')')
{
count = 0;
while(1)
{
if(stack.size() == 0)
{
cout << "Warning!! Number of ')' is greater than '('" << endl;
exit(2);
}
temp = stack.pop();
if(temp != '(')
{
postfix[outpos++] = temp;
}
else
{
break;
}
}
stacktop = stack.return_top();
}
else
{
cout << "Invalid input";
exit(3);
}
if(infix[position] == ')' && infix[position + 1] == '(')
{
stack.push('*');
stacktop = stack.return_top();
}
}
if(stack.size() != 0)
{
cout << "Warning!!Number of '(' is greater than ')'" << endl;
// exit(6);
}
if(!this->return_flag())
{
cout << "You must Enter Numeric value for calculation" << endl;
cout << "This program cannot perform operations on variables";
exit(5);
}
if(this->two_digit_flag)
{
cout << "Sory! Althoug u may have entered right string" << endl;
cout << "this program is only for single digit operation" << endl;
exit(8);
}
postfix[outpos] = '\0';
}
class Evaluate
{
public:
double eval(char expr[], Convert &);
double oper(int symb, double op1, double op2);
};
double Evaluate::oper(int symb, double op1, double op2)
{
switch(symb)
{
case '+': return (op1 + op2);
case '-': return (op1 - op2);
case '*': return (op1 * op2);
case '/': return (op1 / op2);
case '^': return (pow(op1, op2));
}
}
double Evaluate::eval(char expr[], Convert &convert)
{
int c, position;
char temp1;
int count = 0;
double opnd1, opnd2, value;
Stack<double> stack;
for(position = 0; (c = expr[position]) != '\0'; position++)
{
if(convert.isOperand(c))
{
temp1 = double(c - '0');
stack.push(temp1);
}
else
{
opnd2 = stack.pop();
if(stack.size() == 0)
{
cout << "This program cannot process unary operation";
exit(1);
}
opnd1 = stack.pop();
value = oper(c, opnd1, opnd2);
stack.push(value);
}
}
if(stack.size() >= 2)
{
cout << "Sory! this program cannot calculate this" << endl;
cout << "Enter +, *, /, - or ^ between bracket" << endl;
exit(4);
}
return (stack.pop());
}
int main()
{
Convert convert;
Evaluate evaluate;
string bracketted_infix;
char infix[50], postfix[50];
char choice;
while(1)
{
cout << "Enter string: ";
cin >> infix;
cout << endl;
cout << "Entered String: " << infix << endl;
bracketted_infix = convert.return_with_bracket(infix);
convert.to_Postfix(bracketted_infix, postfix);
cout << "Equivalent Postfix string: " << postfix << endl;
cout << "RESULT: ";
cout << evaluate.eval(postfix, convert);
cout << "\nCalculate another string?(y/n) ";
cin >> choice;
cout << endl;
if(choice == 'n')
break;
}
return 0;
}