IF statements

This is a discussion on IF statements within the C++ Programming forums, part of the General Programming Boards category; Hey all. I'm new to programming, and im currently at lesson 2 about If statements. I used the example given ...

  1. #1
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    IF statements

    Hey all.

    I'm new to programming, and im currently at lesson 2 about If statements. I used the example given in the thread, and tried to create one very similar, but it's not made correctly.

    Here is the code, hope someone can tell me whats wrong:

    Code:
    #include iostream
    
    using namespace std;
    
    int main()
    
    {
        int age;
    
        cout<<"How old are you? ";
        cin>> age;
        cin.ignore();
        if (age < 20); {
                cout<<"You are young.\n";
        }
        else if (age = 20) {
             cout<<"You are pretty.\n";
        }
        else (age > 20) {
             cout<<"You are old!\n";
        }
    }

  2. #2
    VA National Guard The Brain's Avatar
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    no semicolon after a 'IF' statement allowed:
    Code:
    if (age < 20);
    'else' is not a conditional statement.. it is a block of code that is executed if all other 'if's or 'else if's' have been attempted:
    Code:
    else (age > 20)
    
    //should just be
    
    else 
    { //stuff here }
    Last edited by The Brain; 03-05-2006 at 07:07 AM.
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  3. #3
    and the hat of int overfl Salem's Avatar
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    > else if (age = 20)
    Also, use == for comparison,
    = is assignment.

  4. #4
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    Hmm.. It's still not working, the program says there is something wrong with this line:

    Code:
    cout<<"Please input your age: ";
    I tried to fix by adding \n, but it's still not working.

    Here's the hole code again:

    Code:
    #include iostream
    
    using namespace std;
    
    int main()
    
    {
        int age;
    
        cout<<"Please input your age: ";
        cin>> age;
        cin.ignore();
        else (age < 20) {
             cout<<"You are young.\n";
        }
        else if (age == 20) {
             cout<<"You are pretty.\n";
        }
        else (age > 20) {
             cout<<"You are old!\n";
        }
    }
    Last edited by Viperz0r; 03-05-2006 at 08:47 AM.

  5. #5
    C++ Witch laserlight's Avatar
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    Your first else should be an if.
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  6. #6
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    Still doesnt work, look at my post again. The program (dev-C++) makes an error at this line, and i really can't see whats wrong. I tried adding \n in the end, but that doesnt help.

    Code:
     cout<<"Please input your age: ";

  7. #7
    and the hat of int overfl Salem's Avatar
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    > The program (dev-C++) makes an error at this line
    Well posting the actual error message would help.

    Also, a single line in isolation doesn't say much. It's also pretty likely that the actual error is on a preceding line and this is just the first line that the compiler notices that there is something wrong.

    For such a short program, reposting the whole thing again is the best course.

  8. #8
    C++ Witch laserlight's Avatar
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    Could be that you use #include iostream instead of #include <iostream>, but the compiler should complain about that.
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  9. #9
    Confused Magos's Avatar
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    #include iostream
    Can't imagine 3 people missed this one
    See anything that's missing?
    MagosX.com

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  10. #10
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    The error line is:
    'cout' undeclared (first use this function).

    This is the hole code:
    Code:
    #include iostream
    
    using namespace std;
    
    int main()
    
    {
        int age;
    
        cout<<"Please input your age: ";
        cin>> age;
        cin.ignore();
        if (age < 20) {
             cout<<"You are young.\n";
        }
        else (age == 20) {
             cout<<"You are pretty.\n";
        }
        else (age > 20) {
             cout<<"You are old!\n";
        }
    }

  11. #11
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    I had to use:

    <iostream>
    instead of
    iostream

    thx for all the replies.

  12. #12
    and the hat of int overfl Salem's Avatar
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    > Here is the code, hope someone can tell me whats wrong:
    Your compiler will tell you what's wrong.

    Code:
    $ g++ foo.cpp
    foo.cpp:1:10: error: #include expects "FILENAME" or <FILENAME>
    foo.cpp: In function ‘int main()’:
    foo.cpp:10: error: ‘cout’ was not declared in this scope
    foo.cpp:11: error: ‘cin’ was not declared in this scope
    foo.cpp:16: error: expected primary-expression before ‘else’
    foo.cpp:16: error: expected `;' before ‘else’
    foo.cpp:19: error: expected primary-expression before ‘else’
    foo.cpp:19: error: expected `;' before ‘else’
    Start at the top, and work your way through the error messages. Just fixing the #include gets rid of 3 errors.

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