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If function is executed without it's condition is true

This is a discussion on If function is executed without it's condition is true within the C++ Programming forums, part of the General Programming Boards category; Hi! I am trying to write a simple program that produces different outputs based on entered age of two different ...

  1. #1
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    Question If function is executed without it's condition is true

    Hi!
    I am trying to write a simple program that produces different outputs based on entered age of two different users.
    Program should tell who is older and behave different if both users are older than 100.

    Here is my program:
    Code:
    #include <iostream>
    using namespace std;
    int main()
    {
        int user1;
        int user2;
        cout << "User1, how old are you:" << endl;
        cin >> user1;
        cout << "User2, how old are you:" << endl;
        cin >> user2;
        if (user1 > user2 )
        {
            if  ((user1 && user2) <= 100)
                {
                 cout << "User1 is older!" << endl;
                }
        }
        else if ( user1 < user2 )
        {
            if ((user1 && user2) <= 100)
            {
             cout << "User2 is older!" << endl;
            }
        }
        else if ( (user1 > 100) && (user2 > 100) )
        {
            cout << "Both users are over 100 years old!" << endl;
        }
        else
        {
            cout << "Users are peers!" << endl;
        }
        cin.get();
        cin.ignore();
    }
    When I enter that user1 is 101 and user2 is 101, output is "Both users are over 100 years old!".

    But when I enter that user1 is 101 and user2 is 105, it gives output that "User2 is older!", instead of "Both users are over 100 years old!", what I actually want it to do.

    It seems that nested if function is executed without it's condition is evaluated true.

    Code:
     else if ( user1 < user2 )
        {
            if ((user1 && user2) <= 100)
            {
             cout << "User2 is older!" << endl;
            }
        }
    I also tryed without nesting, like this:

    Code:
    else if ( user1 < user2 ) && ((user1 && user2) <= 100)
        {
             cout << "User2 is older!" << endl;
        }
    But it didn't work.

    Why program executes this when both users are obviously more than 100, can someone explain me, please?

  2. #2
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    But it didn't work.

    Why program executes this when both users are obviously more than 100, can someone explain me, please?
    Because (user1 && user2) is always less than 100.

    Jim

  3. #3
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    Quote Originally Posted by jimblumberg View Post
    Because (user1 && user2) is always less than 100.

    Jim
    Why?

  4. #4
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    Because you are using the logical AND so if user1 and user2 are equal it evaluates to 1 otherwise it evaluates to zero. You should be using something like
    Code:
    if((user1 <= 100 && user2 <= 100) && (user1 < user2))
    {
       ...

    Jim
    stahta01 likes this.

  5. #5
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    Ok, thanks!

  6. #6
    Captain Crash brewbuck's Avatar
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    You could also just re-arranges some of those if-else clauses to get the right result. Check for the "both users are over 100" first, before doing the other checks.
    Code:
    //try
    //{
    	if (a) do { f( b); } while(1);
    	else   do { f(!b); } while(1);
    //}

  7. #7
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    I solved it this way

    Code:
    #include <iostream>
    using namespace std;
    int main()
    {
        int user1;
        int user2;
        cout << "User1, how old are you:" << endl;
        cin >> user1;
        cout << "User2, how old are you:" << endl;
        cin >> user2;
        if ( !((user1 > 100) && (user2 > 100)) )  // Execute, except if user1 and user2 are not bigger than 100
        {
            if ( user1 < user2 )
            {
                cout << "User2 is older!" << endl;
            }
            else if ( user1 > user2 )
            {
                cout << "User1 is older!" << endl;
            }
            else
            {
                cout << "Users are peers!" << endl;
            }
        }
        else                                             //otherwise execute this
        {
            cout << "Both users are over 100 years old!" << endl;
        }
        cin.get();
        cin.ignore();
    }
    Everything is more clear now, thanks!

  8. #8
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    I propose a solution a bit simpler:

    Code:
    #include <iostream>
    using namespace std;
    int main()
    {
        int user1;
        int user2;
        cout << "User1, how old are you:" << endl;
        cin >> user1;
        cout << "User2, how old are you:" << endl;
        cin >> user2;
        cin.ignore();
    
        if (user1 > 100 && user2 > 100)
        {cout << "Both users are over 100 years old!" << endl;}
        else 
        { 
            if (user1 > user2)
            {cout << "User1 is older!" << endl;}
            else {cout << "User2 is older!" << endl;}
        }
    
        cin.get();
    }

  9. #9
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    Well, your solution is much more elegant, but I just don't like that program says that User2 is older when they are both of same age, so I added one more function to your solution:

    Code:
    #include <iostream>
    using namespace std;
    int main()
    {    int user1;
         int user2;
            cout << "User1, how old are you:" << endl;
            cin >> user1;
            cout << "User2, how old are you:" << endl;
            cin >> user2;
            cin.ignore();
            if (user1 > 100 && user2 > 100)
            {cout << "Both users are over 100 years old!" << endl;}
            else
            {
                if (user1 > user2)
                {cout << "User1 is older!" << endl;}
                else if (user1 < user2)
                {cout << "User2 is older!" << endl;}
                else {cout << "Users are peers!" << endl;} //The third possibility
            }
            cin.get();
    }
    Now it's perfect
    Last edited by Cjof; 03-06-2013 at 03:11 PM.

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