Stacks with Chars

[Student1904]

Hello, I cant seem to get my code to work. Any advice?

#include<iostream>
using namespace std;

class stack
{
private:
	char a[80];
	int counter;
public:
	void clearStack(){counter = 0;}
	bool emptyStack(){if(counter = 0) return true; else return false;}
	bool fullStack(){if(counter = 80) return true; else return false;}
	void pushStack(char x){a[counter] = x; counter++;}
	char popStack(){counter--; return a[counter];}
};

bool isvowel(char x)
{
	x = toupper(x);
	if(x == 'A' ||
		x == 'E' ||
		x == 'I' ||
		x == 'O' ||
		x == 'U') return true; else return false;
}

int main()
{
	stack UPP, LOW, VOW;

	char c;

	cout << "Enter a sentence: ";
	while(cin.get(c))
	{
		if(isupper(c)) UPP.pushStack(c);
		if(islower(c)) LOW.pushStack(c);
		if(isvowel(c)) VOW.pushStack(c);
	}

	cout << "Uppercase letters: ";
	while(!UPP.emptyStack())
	{
		char y = UPP.popStack();
		cout << y;
	}
	cout << endl;

	cout << "Lowercase letters: ";
	while(!LOW.emptyStack())
	{
		char y = LOW.popStack();
		cout << y;
	}

	cout << "Vowels; ";
	while(!VOW.emptyStack())
	{
		char y = VOW.popStack();
		cout << y;
	}
}

[ne555]

> I cant seem to get my code to work
you need to be more descriptive

	bool emptyStack(){if(counter = 0) return true; else return false;}
	bool fullStack(){if(counter = 80) return true; else return false;}

= is assignment
== is comparison

[mbozzi]

#include <iostream>
using namespace std;

class stack {
  // NOTE(mbozzi): A constant number max_size is used to avoid writing 80
  // everywhere.
  static int const max_size = 80;

  char a[ max_size ]{};

  // `counter' always contains the index of the next element
  int  counter = 0;

public:
  void clear()       { counter = 0; }
  
  // two equals signs are required to test for equality.
  bool empty() const { return counter == 0; }
  bool full() const  { return counter == max_size; }

  void push(char x)  { a[ counter++ ] = x; }
  char pop()         { return a[ --counter ]; }
};

bool isvowel(char x) {
  x = toupper(x);
  return x == 'A' || x == 'E' || x == 'I' || x == 'O' || x == 'U';
}

void display_stack(stack s) {
  while (!s.empty())
    std::cout << s.pop() << " ";

  std::cout << '\n';
}

int main() {
  stack upper, lower, vowels;

  cout << "Enter a sentence: ";
  for (char c; cin.get(c); ) {
    if (isupper(c)) upper.push(c);
    if (islower(c)) lower.push(c);
    if (isvowel(c)) vowels.push(c);
  }

  cout << "Uppercase letters: ";
  display_stack(upper);

  cout << "Lowercase letters: ";
  display_stack(lower);

  cout << "Vowels: ";
  display_stack(vowels);
}