C++ Bug probably scope problem


 
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Old 08-28-2014
C++ Bug probably scope problem

Hello,
I have some difficulty to understand the scope of this program adapted from C++ book of D.S. Malik I am reading.
I put the header and the main program as attachment to save space. My problem is the output:
Code:
$ ./prog1009_die
Line 4: Not yet rolled, die1 gets default number: 1
Line 5: Not yet rolled, die2 gets default number: 1

Line 6: After first rolling die1: 4
Line 7: After first rolling die2: 5
Line 8: The sum of the numbers rolled by the dice is: 9

Line 6-2: After second rolling die1: 2
Line 7-2: After second rolling die2: 4

Line 9: After rolling again (third time), 
die1 (die1.roll()): 5
die2 (die2.roll()): 4
the sum of the numbers rolled [die1.getNum() + die2.getNum()] is: 8
the sum of the numbers rolled [die1.roll() + die2.roll()] is: 8

Line 9-2: After rolling again (third time)
die1 (die1.getNum()): 5
die2 (die2.getNum()): 4
the sum of the numbers rolled [die1.getNum() + die2.getNum()] is: 9

I was expecting Line 9 part would be the same result as Line 9-2 part, but the sum of the two numbers is not right. It is difficult for me to understand why. The problem may be related to die::roll() and die::getNum() functions in this case, but I am not sure.
Code:
int die::roll()
{
    num = rand() % 6 + 1;
    return num;
}

int die::getNum() const
{
    return num;
}

Also I am aware the rand() function here so each time the number will change. Can somebody elaborate it for me? Thanks a lot!

Last edited by yifangt; 08-28-2014 at 04:29 PM.. Reason: typos
 
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