I have an assignment where we have to do some stuff with postfix and infix operations. My professor provided all of the code to us with a section of the code in main empty for us to perform certain postfix operations. I am trying to implement the Stack template he provided with strings but it is not working. Here is the code for main (you can ignore all the commented out part):
#include "stack.hpp"
using namespace std;
int main()
{
cout << endl << "Start" << endl;
Stack<string> stack;
//string s = "hello world";
//char s = 'h';
//stack.push(s);
//cout << endl << endl << stack.pop() << endl << endl;
return 0;
}
/*
// Auxiliary method, you probably find it useful
// Operands are all lower case and upper case characters
bool isOperand(char c){
return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z');
}
// Auxiliary method, you probably find it useful
int precedence(char c)
{
if(c == '+' || c == '-'){
return 0;
}
if(c == '*' || c == '/'){
return 1;
}
if(c == '^'){
return 2;
}
return -1;
}
int main(){
cout << endl << "start" << endl;
freopen("input_postfix2infix.txt", "r", stdin);
string input;
string solution;
int line_counter = 0;
cout << endl << "before loop" << endl;
while(cin >> solution){
cin >> input;
Stack<string> stack;
string result;
//The input file is in the format "expected_solution infix_expression",
//where expected_solution is the infix_expression in postfix format
string s = "hello world";
//char s = 'h';
stack.push(s);
cout << endl << endl << stack.pop() << endl << endl;
//cout << input << endl << endl;
for(int i=0; i<input.length(); ++i){
char c = input.at(i);
if(isalnum(c))
{
string s;
s.push_back(c);
stack.push(s);
}
else
{
if(c == '+')
{
string a = stack.pop();
string b = stack.pop();
string sum = a + '+' + b;
sum = '(' + sum + ')';
stack.push(sum);
}
else if(c == '-')
{
string a = stack.pop();
string b = stack.pop();
string diff = b + '-' + a;
diff = '(' + diff + ')';
stack.push(diff);
}
else if(c == '*')
{
string a = stack.pop();
string b = stack.pop();
string prod = a + '*' + b;
prod = '(' + prod + ')';
stack.push(prod);
}
else if(c == '/')
{
string a = stack.pop();
string b = stack.pop();
string quot = b + '/' + a;
quot = '(' + quot + ')';
stack.push(quot);
}
else if(c == '^')
{
string exp = stack.pop();
string a = stack.pop();
string power = a + '^' + exp;
power = '(' + power + ')';
stack.push(power);
}
}
// WRITE CODE HERE to store in 'result' the postfix transformation of 'input'
}
result = stack.pop();
// You need to do some extra stuff here to store in 'result' the postfix transformation of 'input'
// Checking whether the result you got is correct
if(solution == result){
cout << "line " << line_counter << ": OK [" << solution << " " << result << "]" << endl;
}else{
cout << "line " << line_counter << ": ERROR [" << solution << " " << result << "]" << endl;
}
line_counter++;
}
}
*/
If I comment out the stack declaration ("Stack<string> stack;") then the program compiles and when it runs, "Start" is outputted. However, if I include the stack declaration, the program seems to compile successfully again, but when I run it, absolutely nothing happens. That's why I commented out all the rest of the code, so I can test it out on a smaller scale, and still nothing. I have even included the template string declaration at the end of the Stack cpp file my professor provided.
Here is Stack.hpp provided by my professor:
//#include <bits/stdc++.h>
#include<iostream>
#include<cstring>
#include<cmath>
#include<cstdio>
// Ideally this would not be a huge number, you could also use a vector
#define MAXSIZE 100000
using namespace std;
template<class T>
class Stack{
private:
T arr[MAXSIZE]; // the actual stack
int topIndex; // index of the top element
public:
Stack(){
topIndex = -1; // constructor
};
~Stack(){}; // destructor
void push(T c); // push c to the list
T pop(); // return and remove the top element in the stack
T peek(); // return the top element in the stack
int size(); // returns the size of the stack
void display(); // display the stack in stdout
};
Here is Stack.cpp also provided by my professor (I added the "template class Stack<string>;" at the end):
#include "stack.hpp"
using namespace std;
template<class T>
void Stack<T>::push(T c){
if(topIndex > MAXSIZE-1){
cout<<"Stack overflow"<<endl;
return;
}
arr[topIndex + 1] = c;
topIndex++;
}
template<class T>
T Stack<T>::pop(){
if(topIndex < 0){
cout<<"Cannot delete. Stack empty."<<endl;
}
return arr[topIndex--];
}
template<class T>
T Stack<T>::peek(){
if(topIndex < 0){
cout<<"Cannot peek. Stack empty."<<endl;
}
return arr[topIndex];
}
template<class T>
int Stack<T>::size(){
return topIndex+1;
}
template<class T>
void Stack<T>::display(){
for(int i=topIndex; i>=0; --i){
cout<<arr[i]<<"\t";
}
cout<<endl;
}
template class Stack<char>;
template class Stack<int>;
template class Stack<string>;
I don't understand what is going on. I thought adding the declaration at the end of Stack.cpp would fix ALL the issues I was having (before, I was getting a bunch of "undefined reference too..." errors) but, now I have this issue too. Could someone please help me too understand why this isn't working? Any help would be greatly appreciated. By the way, everything works perfectly with "Stack<int>" and "Stack<char>", its just "Stack<string>" where I have this problem. Thank you.
I have tried reading a BUNCH of other answers to questions similar to this one but none of them answers my issue. I have used the approach of explicitly instantiating the implementation I will use at the end of the .cpp file and yet my program is still not working. I do not want to move everything into the header file since the file is not originally mine (I only want to make minor edits and only if I absolutely have to).
