function loop help

This is a discussion on function loop help within the C++ Programming forums, part of the General Programming Boards category; I'm writing a calendar program and I need help with a function called getMonth(). It's supposed to return a single ...

  1. #1
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    function loop help

    I'm writing a calendar program and I need help with a function called getMonth().

    It's supposed to return a single value as the output: the month number that the user entered. It also ensures that the month is in the acceptable range (1 ≤ month ≤ 12) . If the user enters a month outside that range, then getMonth() keeps prompting him or her until an acceptable value is found.

    Here's what I came up with:

    Code:
    int getMonth()
    {
       int month;
       cout << "Enter a month number: ";
       cin >> month;
       for (month = 1; month = 12; month++)
       {
          int month;
          if (month > 12)
             cout << "Month must be between 1 and 12";
       }
       return month;
    }
    the problem is that whenever I enter in any number, regardless of whether it fits the parameters of 1 and 12, it goes through an infinite cycle.

    I DON'T KNOW WHAT TO DO!!!!
    please help

  2. #2
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    That should be "month == 12" (note the double equal signs).

    Also, declaring another "month" inside the for loop is going to mess up your comparison. Don't you want to compare 12 against the "month" you created at the beginning of the main function instead?
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  3. #3
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    ok, so I revised it some, and used a while statement instead of a for.

    Code:
    int getMonth()
    {
       int month;
       cout << "Enter a month number: ";
       cin >> month;
       while ( month < 1 || month > 12)
       {
          cout << "\nMonth must be between 1 and 12";
       }
       return 0;
    }
    but this still runs through the string forever. What am I doing wrong?

  4. #4
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    You are not modifying "month" inside the while loop. Therefore once you go into the loop, there is no way to exit. You might want to read about a do/while loop for this sort of problem since it's better suited.

    Code:
    #include <iostream>
    
    int main(void)
    {
        int month;
        do  
        {   
            std::cout << "Enter a month number: ";
            std::cin >> month;
        } while(month < 1 || month > 12);
        std::cout << "You entered: " << month << std::endl;    
    }
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  5. #5
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    I really do not know how to modify month. I know that this is extremely basic, but im extremely new to programming. how do I modify the variable so that the loop can exit?

  6. #6
    Registered User rogster001's Avatar
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    I really do not know how to modify month. I know that this is extremely basic, but im extremely new to programming. how do I modify the variable so that the loop can exit?
    Did you actually read the code example that was posted for you? You could even compile and run it, it will all become clear!
    But in any case just think about it properly, in your original code you are saying literally that "WHILST the month number fits this condition keep running" And if you look, Nothing in your code does anything to change 'month'.
    Once the loop has started the program cannot go anywhere except keep executing the loop until something happens to stop it E.G. fail the condition in the While statement.
    In the example that was posted, the user is asked to input a value for month, everything will now work as the condition that is keeping the loop running has a chance to be changed and thus exit loop.
    Also make sure you initialise (ie set a value of 0 or whatever) your variable before using it to control a while loop, or any other loop.
    In general always initialise variables, unless you like unneccesary debugging!
    Last edited by rogster001; 02-25-2011 at 01:59 AM.
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  7. #7
    C++まいる!Cをこわせ! Elysia's Avatar
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    Quote Originally Posted by akahizzle View Post
    I really do not know how to modify month. I know that this is extremely basic, but im extremely new to programming. how do I modify the variable so that the loop can exit?
    Current loop logic:

    WHILE month < 1 || month > 12
    PRINT "Month must be between 1 and 12"
    REPEAT

    Now modify that logic so it's right.
    Quote Originally Posted by Adak View Post
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    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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