c++ calculater (need help with pointer and trigger??)

[gamer]

i have written this c++ code a few days ago,
now my problem is i want to have the user input and check if its y or n but i get this error message

ANSI c++ forbits comparison between pointers and triggers

here's my c++ code

#include <iostream.h>
#include <stdlib.h>

int main()
{
      int choice;
      int x1;
      int x2;
      int mem1;
      int mem2;
      int answer;
      char drie ;
      cout <<" 1 = +\n";
      cout <<" 2 = -\n";
      cout <<" 3 = *\n";
      cout <<" 4 = /\n";
      cout <<" 5 = %\n";
      cout <<" 6 = documentation/license\n";
      cout <<" enter your choice: \n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n ";
      cin>>choice;
      if (choice == 1){
      cout <<"\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\nnenter number 1: ";
      cin>>x1;
      cout <<"\nenter number 2: ";
      cin>>x2;
      answer = x1 + x2;
      cout <<"your answer :"<<answer<<"\n";
      }
      if (choice == 2){
      cout <<"\nenter number 1: ";
      cin>>x1;
      cout <<"\nenter number 2: ";
      cin>>x2;
      answer = x1 - x2;
      cout <<"your answer :"<<answer<<"\n";
      }
      if (choice == 3){
      cout <<"\nenter number 1: ";
      cin>>x1;
      cout <<"\nenter number 2: ";
      cin>>x2;
      answer = x1 * x2;
      cout <<"your answer :"<<answer<<"\n";
      }
      if (choice == 4){
      cout <<"\nenter number 1: ";
      cin>>x1;
      cout <<"\nenter number 2: ";
      cin>>x2;
      answer = x1 / x2;
      cout <<"your answer :"<<answer<<"\n";
      }
      if (choice == 5){
      cout <<"\nenter number 1: ";
      cin>>x1;
      cout <<"\nenter number 2: ";
      cin>>x2;
      answer = x1 % x2;
      cout <<"your answer :"<<answer<<"\n";
      }
      if (choice == 6){
      cout <<"\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n";
      cout <<"welcome to tech calculator(TM) (c) stefan feenstra\n\n";
      cout <<"you may not debug or do anything to get the source code\n";
      cout <<"calculater is written in c++ 77 lines of code\n";
      cout <<"this software is freeware, you may redristrubute BUT\n";
      cout <<"you must leave a link to the official website\n";
      cout <<"due to this software is Freeware the auther takes\n"   ;
      cout <<"no responsibillety, if you do not agree to these terms,\n"  ;
      cout <<"you may not use this software\n\n\n\n";
      cout <<"known bugs, when typing a letter at a calculation you cant\n"               ;
      cout <<"type in a second number, or the program will terminate or something else\n";
      cout <<"if you need to report a bug you can send it to [email protected]\n";
      cout <<"under title of \'TECH CALCULATER BUG\'";
      }
      if (choice != 1 && choice != 2 && choice != 3 && choice != 4 && choice != 5 && choice != 6){
      cout <<"\na error acured you entered a wrong number/letter you entered as choice\'"<<choice<<"\'";
      }
      //system("PAUSE");
      cout <<"return ? 1 or 0 : ";
      cin>>drie;
      if (drie == "y"){
      cout <<"\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n";
      return main();
      }
      if (drie != "n"){
      return 0;
}
}

P.S. sorry i did not commend it

[Thantos]

you mind showing which line gives the error

also iostream.h is depreated. Do a quick search and you'll find the details about that.

[gamer]

the error are in these two lines

      //system("PAUSE");
      cout <<"return ? y or n : ";
      cin>>drie;
      if (drie == "y"){ //error
      cout <<"\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n";
      return main();
      }
      if (drie != "n"){ //second error
      return 0;
}
}

the two errors are the same so i only posted them once

[Salem]

> if (drie == "y"){ //error
drie is a char, not a string

So use a char constant to compare with - single quotes
if (drie == 'y')

[gamer]

thanks for helping me,
no i have a bug when i hit y it just exites the application,
but he needs to return to main for a other calculation

[Lithorien]

Ok. Let me introduce you to a very nice concept called "switch..case".

Your code originally makes use of a lot of if..than statements. Granted this is valid, but it leaves you more likely to make mistakes. Take a look at this and see if you can make heads or tails of it:

#include <iostream.h>
#include <stdlib.h>

int main()
{
      int choice;
      int x1;
      int x2;
      int answer;
      char drie ;
      	  
	  cout << "1 = +\n";
      cout << "2 = -\n";
      cout << "3 = *\n";
      cout << "4 = /\n";
      cout << "5 = %\n";
      cout << "6 = Documentation/License\n\n";
      cout << "Enter your choice: ";
      cin >> choice;
	  cout << "\n";

	  switch (choice)
	  {
		case 1:
			cout << "Enter first number: ";
			cin >> x1;

			cout << "Enter second number: ";
			cin >> x2;

			answer = (x1 + x2);

			cout << "\nYour answer: " << answer << "\n\n";
		break;

		case 2:
			cout << "Enter first number: ";
			cin >> x1;
			
			cout << "Enter second number: ";
			cin >> x2;
			
			answer = (x1 - x2);
			
			cout << "\nYour answer: " << answer << "\n\n";
		break;
      
		case 3:
			cout << "Enter first number: ";
			cin >> x1;
			
			cout << "Enter second number: ";
			cin >> x2;
			
			answer = (x1 * x2);
			
			cout << "\nYour answer: " << answer << "\n\n";
		break;

		case 4:
			cout << "Enter first number: ";
			cin >> x1;
			
			cout << "Enter second number: ";
			cin >> x2;
			
			answer = (x1 - x2);
			
			cout << "\nYour answer: " << answer << "\n\n";
		break;
      
		case 5:
			cout << "Enter first number: ";
			cin >> x1;
			
			cout << "Enter second number: ";
			cin >> x2;
			
			answer = (x1 % x2);
			
			cout << "\nYour answer: " << answer << "\n\n";
		break;
      
		case 6:
			cout <<"\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n";
			cout <<"welcome to tech calculator(TM) (c) stefan feenstra\n\n";
			cout <<"you may not debug or do anything to get the source code\n";
			cout <<"calculater is written in c++ 77 lines of code\n";
			cout <<"this software is freeware, you may redristrubute BUT\n";
			cout <<"you must leave a link to the official website\n";
			cout <<"due to this software is Freeware the auther takes\n"   ;
			cout <<"no responsibillety, if you do not agree to these terms,\n"  ;
			cout <<"you may not use this software\n\n\n\n";
			cout <<"known bugs, when typing a letter at a calculation you cant\n"               ;
			cout <<"type in a second number, or the program will terminate or something else\n";
			cout <<"if you need to report a bug you can send it to [email protected]\n";
			cout <<"under title of \'TECH CALCULATER BUG\'";
		break;

		default:
			cout << "An error occured: You selected an invalid choice: " << choice << "\n\n";
      }
      
      cout << "Enter another function? ";
      cin >> drie;

	  switch (drie)
	  {
		case 'Y':
			main();
		break;

		case 'y':
			main();
		break;

		case 'N':
			return(0);
		break;

		case 'n':
			return(0);
		break;

		default:
			return(0);
	  }
      
	  return(0);
}

Hope this helps!

[gamer]

yeah that helps thanks for all the help guys
and that latest post of me i forgot to change int to char,
that was kind of stupid

[Thantos]

Except that you aren't allowed to call main() anymore. Just put everything in a loop. Also there is no real need for:

case 'N':
  return 0;
  break;
case 'n':
  return 0;
  break;

There are a couple ways around it:
way 1:

switch (tolower(drie))
{
  case 'n':
    return 0;
  case 'y'
    // do something
    break;
}

Way 2:

switch(drie)
{
  case 'n':
  case 'N':
    return 0; // no need for a break after this
  case 'Y':
  case 'y':
    //do something
    break;
}

[Lithorien]

Except that you aren't allowed to call main() anymore. Just put everything in a loop. Also there is no real need for:

case 'N':
  return 0;
  break;
case 'n':
  return 0;
  break;

There are a couple ways around it:
way 1:

switch (tolower(drie))
{
  case 'n':
    return 0;
  case 'y'
    // do something
    break;
}

Way 2:

switch(drie)
{
  case 'n':
  case 'N':
    return 0; // no need for a break after this
  case 'Y':
  case 'y':
    //do something
    break;
}

That's all very true. I just used main() because he used it and really didn't want to code a loop for him. That's his job.

As for the ways around the multiple cases, I never considered tolower - thanks! That'll help in some of my programs (I literally have 52 case statements, I can cut that in half).

[Sang-drax]

That'll help in some of my programs (I literally have 52 case statements, I can cut that in half).

Wow. I hope that I don't see that code. Ever.
The length of that switch statement must be staggering, considering that many statements within your case-blocks are exactly the same in your example.
Keyboards aren't expensive, but a little saving could help nevertheless.

[Sebastiani]

	  switch (choice)
	  {
		case 1:
			cout << "Enter first number: ";
			cin >> x1;

			cout << "Enter second number: ";
			cin >> x2;

			answer = (x1 + x2);

			cout << "\nYour answer: " << answer << "\n\n";
		break;

		case 2:
			cout << "Enter first number: ";
			cin >> x1;
			
			cout << "Enter second number: ";
			cin >> x2;
			
			answer = (x1 - x2);
			
			cout << "\nYour answer: " << answer << "\n\n";
		break;

you should really avoid duplication of code whenever possible. a better way would be something like:

 cin >> choice;
 cout << "\n";
 if(choice < 1 || choice > 6) {
  // ...report...
  } else {
  cout << "Enter first number: ";
  cin >> x1;
  cout << "Enter second number: ";
  cin >> x2;
  switch (choice) {
   case 1: answer = (x1 + x2);
   break;
   //...etc...
   }
 cout << "\nYour answer: " << answer << "\n\n";
 }

also noticed a typo here - you subtract when you were supposed to divide:

case 4:
			cout << "Enter first number: ";
			cin >> x1;
			
			cout << "Enter second number: ";
			cin >> x2;
			
			answer = (x1 - x2);

...but don't forget - divide by zero is a big no-no, so be sure to check for that...

[edit]
damn I'm slow. =)
[/edit]

[Lithorien]

Wow. I hope that I don't see that code. Ever.
The length of that switch statement must be staggering, considering that many statements within your case-blocks are exactly the same in your example.
Keyboards aren't expensive, but a little saving could help nevertheless.

It is pretty staggering. I also havn't gone through and optomized yet, so my code just works. :P

Yeah. I believe I have 300 lines in that switch statement alltogether. It's a thing of great fear. O.O

[VirtualAce]

If you want to make a better expression parser google for recursive decent parsers.