C++ program assistance needed

This is a discussion on C++ program assistance needed within the C++ Programming forums, part of the General Programming Boards category; Hello all, I've got a question regarding a programming assignment that is due by midnight. The objective is to create ...

  1. #1
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    Question C++ program assistance needed

    Hello all,

    I've got a question regarding a programming assignment that is due by midnight. The objective is to create a program that converts a binary number (up to 32 bits long) to decimal. The problems I have run up against thus far are:

    1) Without the error checking for an entry being 1 or 0, I have a problem getting the original binary number to be displayed on the "____ in binary is ____ in decimal." line.
    2) With error checking, it keeps automatically passing by the binary number entry line and saying that it is not a valid binary number.

    Here is my current code:
    Code:
    #include <iostream>
    #include <iomanip>
    using namespace std;
    int main()
    {
      char entry[32];
      char decision, exit_option;
      int place = 0, digit, decimal = 0;
      int n = 0, power = 1;
    
      cout << "This program converts positive integer binary numbers"
           << " (up to 32 bits) into a decimal number.\n\n"
           << "Would you like to convert a binary number? (Y or y): ";
      cin >> decision;
      exit_option = 'Y';
    
      while((exit_option == 'Y')||(exit_option == 'y'))
      {
        if((decision == 'Y')||(decision == 'y'))
          {
          cout << "\n\nPlease enter your binary number:\n\n";
          cin >> entry[0];
          while (entry[place] != '\n')
            {
            place ++;
            cin >> noskipws >> entry[place];
            }
          if((entry[place] != 1)||(entry[place] != 0))
            {
            cout << "\n\nThis is not a binary number. Try again? ";
            cin >> exit_option;
            }
          else
            {
            for(digit = place-1; digit >= 0; digit --)
              {
              decimal += (entry[digit] - '0')*power;
              power *= 2;
              }
            cout << entry[place] << "in binary is " << decimal << " in decimal.\n\n";
            cout << "Continue? (Y or y): ";
            cin >> exit_option;
            }
          }
        else
          {
          cout << "Thanks anyway!";
          exit_option = 'n';
          }
      }
      cout << "\n\nThank you for using the Binary Number Convertor!\n\n";
      return 0;
    }
    Thanks for any help/advice given.

  2. #2
    and the Hat of Guessing tabstop's Avatar
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    There's a difference between 1 (the number 1) and '1' (the character '1'). Since you're reading in characters, you should probably consider that entry[place] might be '1' or '0' rather than 1 or 0.

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    I re-introduced the single quotes around the 0 and 1 and the same result holds. It's something in the order/placement of the if, skipws/noskipws, or something.

  4. #4
    and the Hat of Guessing tabstop's Avatar
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    Does it choke before the \n, or on the \n itself? (Notice that you read in the new-line character and then run the error check, before the while loop can stop you.)

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    After running the program, here's what happens:

    First time through, it allows me to enter a binary number. After hitting enter, it comes up with the "This is not a binary number." line. When asked to continue and I input yes (y), it jumps back and again goes through to the "This is not a binary number." line without allowing me to enter a number.

    Code:
    This program converts positive integer binary numbers (up to 32 bits) into a decimal number.
    
    Would you like to convert a binary number? (Y or y): y
    
    
    Please enter your binary number:
    
    101
    
    
    This is not a binary number. Try again? y
    
    
    Please enter your binary number:
    
    
    
    This is not a binary number. Try again? y
    
    
    Please enter your binary number:
    
    
    
    This is not a binary number. Try again? y
    
    
    Please enter your binary number:
    
    
    
    This is not a binary number. Try again? n
    
    
    Thank you for using the Binary Number Convertor!

  6. #6
    and the Hat of Guessing tabstop's Avatar
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    The not-being-able-to-do-a-second-try is due to your not resetting place before re-reading. And I'm still guessing that nothing-being-a-binary-number is due to the mishandling of the \n.

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    Quote Originally Posted by tabstop View Post
    The not-being-able-to-do-a-second-try is due to your not resetting place before re-reading. And I'm still guessing that nothing-being-a-binary-number is due to the mishandling of the \n.
    I'm not quite sure what you're getting at here then with the \n bit - d'you mean the while statement involving \n? That's the only place where it's used as a character. Would I need to move the error check of the "if" into the while statement? I'm confused.

  8. #8
    and the Hat of Guessing tabstop's Avatar
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    Quote Originally Posted by Velocity View Post
    I'm not quite sure what you're getting at here then with the \n bit - d'you mean the while statement involving \n? That's the only place where it's used as a character. Would I need to move the error check of the "if" into the while statement? I'm confused.
    Well, yes; at the moment the only character you ever check to see if it is a 1 or a 0 is the \n at the end, since the check only happens after you are done with the while loop.

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    All right, but when I do that the program goes insane. I just don't know where/when this error check should occur. When I don't have it in the program AT ALL, the program compiles and runs without much problem:

    Code:
    #include <iostream>
    #include <iomanip>
    using namespace std;
    int main()
    {
      char entry[32];
      char decision, exit_option;
      int place = 0, digit, decimal = 0;
      int n = 0, power = 1;
    
      cout << "This program converts positive integer binary numbers"
           << " (up to 32 bits) into a decimal number.\n\n"
           << "Would you like to convert a binary number? (Y or y): ";
      cin >> decision;
      exit_option = 'Y';
    
      while((exit_option == 'Y')||(exit_option == 'y'))
      {
        if((decision == 'Y')||(decision == 'y'))
          {
          cout << "\n\nPlease enter your binary number:\n\n";
          cin >> entry[0];
          while (entry[place] != '\n')
            {
            place ++;
            cin >> noskipws >> entry[place];
            }
          for(digit = place-1; digit >= 0; digit --)
            {
            decimal += (entry[digit] - '0')*power;
            power *= 2;
            }
          cout << entry[place] << "in binary is " << decimal << " in decimal.\n\n";
          cout << "Continue? (Y or y): ";
          cin >> exit_option;
          }
        else
          {
          cout << "Thanks anyway!";
          exit_option = 'n';
          }
      }
      cout << "\n\nThank you for using the Binary Number Convertor!\n\n";
      return 0;
    }
    The problem with THIS code is that it does not display the binary number at the end "____ in binary is ____ in decimal."

  10. #10
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    Never mind, it doesn't work without difficulty.

  11. #11
    and the Hat of Guessing tabstop's Avatar
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    You need to print entry, not entry[place], as that will (still) only print the newline character and not the whole thing.

    And you still need to set place back to 0 before trying to read in a second number.

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    I scrapped the one without error check -- after trying a 32-bit number it decided to display it as being -1 in decimal. :-/

    This is beginning to frustrate... even after setting place back to 0 at the top of the while loop and taking out entry[place] (inserting entry instead, is that what you meant?) it does the same thing.

  13. #13
    and the Hat of Guessing tabstop's Avatar
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    Quote Originally Posted by Velocity View Post
    I scrapped the one without error check -- after trying a 32-bit number it decided to display it as being -1 in decimal. :-/
    You say that as though that is incorrect. However, 11111111111111111111111111111111 is -1. (Or, more specifically, how -1 is represented in most computers these days.)
    Quote Originally Posted by Velocity View Post
    This is beginning to frustrate... even after setting place back to 0 at the top of the while loop and taking out entry[place] (inserting entry instead, is that what you meant?) it does the same thing.
    You'll have to show me what you mean.

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    Quote Originally Posted by tabstop View Post
    You say that as though that is incorrect. However, 11111111111111111111111111111111 is -1. (Or, more specifically, how -1 is represented in most computers these days.)
    ...I knew that.

    <_<
    >_>

    You'll have to show me what you mean.
    Where "entry[place]" was in the original code, I replaced with just "entry". I don't think that's right though.

    The second bit of code (the one without the error check) runs the first time correctly, then upon re-entrance into the loop it goes nuts again and displays the same number over again. Code is below...

    Code:
    #include <iostream>
    #include <iomanip>
    using namespace std;
    int main()
    {
      char entry[32];
      char decision, exit_option;
      int place = 0, digit, decimal = 0;
      int n = 0, power = 1;
    
      cout << "This program converts positive integer binary numbers"
           << " (up to 32 bits) into a decimal number.\n\n"
           << "Would you like to convert a binary number? (Y or y): ";
      cin >> decision;
      exit_option = 'Y';
    
      while((exit_option == 'Y')||(exit_option == 'y'))
      {
        if((decision == 'Y')||(decision == 'y'))
          {
          place = 0;
          cout << "\n\nPlease enter your binary number:\n\n";
          cin >> entry[0];
          while (entry[place] != '\n')
            {
            place ++;
            cin >> noskipws >> entry[place];
            }
          for(digit = place-1; digit >= 0; digit --)
            {
            decimal += (entry[digit] - '0')*power;
            power *= 2;
            }
          cout << entry << "in binary is " << decimal << " in decimal.\n\n";
          cout << "Continue? (Y or y): ";
          cin >> exit_option;
          }
        else
          {
          cout << "Thanks anyway!";
          exit_option = 'n';
          }
      }
      cout << "\n\nThank you for using the Binary Number Convertor!\n\n";
      return 0;
    }
    Last edited by Velocity; 10-05-2008 at 07:23 PM.

  15. #15
    and the Hat of Guessing tabstop's Avatar
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    cin >> exit_option leaves a \n in the input buffer, which is cheerfully read into input[0] at the top of the next loop. Adding "cin.ignore()" directly after this works wonders. (Edit: I mean directly after cin>>exit_option.)

    Next, you will discover that power isn't reset, and that maybe you want to reset your input array too.

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