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

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

Code:

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ANSI c++ forbits comparison between pointers and triggers

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here's my c++ code

Code:

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#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;
}
}

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P.S. sorry i did not commend it

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.

the error are in these two lines

Code:

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      //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;
}
}

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

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

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

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

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:

Code:

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#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!

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

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

Code:

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

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There are a couple ways around it:
way 1:

Code:

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

---

Way 2:

Code:

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

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Quote:

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Originally Posted by Thantos

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

Code:

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

---

There are a couple ways around it:
way 1:

Code:

---

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

---

Way 2:

Code:

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

---

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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).

Quote:

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Originally Posted by Lithorien

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

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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. :)

Code:

---

          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:

Code:

---

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:

Code:

---

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

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...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]

Quote:

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Originally Posted by Sang-drax

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. :)

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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

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