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Class, please explain to me:

int i; if ((i%2==0) && (i%4==0)) will give the same output with the following if statement: if (i%8==0); Thank you.

6th Nov 2022, 1:07 PM
Oliver Pasaribu
Oliver Pasaribu - avatar
6 Answers
+ 3
Oliver Pasaribu As there is && so only number divided by (2 * 4 = 8) will be print in 1st case which is similar to 2nd case. If there is or (||) then outputs will be different in both cases. or (||) means number divided by either 2 or 4
6th Nov 2022, 1:27 PM
A͢J
A͢J - avatar
+ 3
Oliver Pasaribu only the lowest common multiple (LCM) of 2 and 4 will give the same result. So in fact, (i%8==0) is not the same. The LCM of 2 and 4 is 4, so only (i%4==0) is the same. Proof: try i=12. It passes for (i%2==0 && i%4==0), and (i%4==0), but fails for (i%8==0). It works because the value of i must be a multiple of both factors (2 and 4) in order for the remainder to be zero for both. Therefore, by using the modulo of the lowest common multiple, you are assured that it is also a multiple of both.
6th Nov 2022, 9:23 PM
Brian
Brian - avatar
+ 1
Does (i%4)&&(i%2) equivalen with (i%8); i%4 means each int value of i that is divisible by 4 (result integer part only, no remainder, i%4=0) divisible by 4: 0,4,8,12,16,20,24, ... divisible by 2: 0,2,4,6,8,10,12,14,16,18,20,.. divisible by 8: 0,8,16,24,32,40,48,56,64,72,80,... So, .divisible by 2 AND 4 must be: 4,8,12,16,20,24,28,e2,36,40,... divisible be 8: 0,8,16,24,32,40,48,56,64,72,80 Oh I see, this two statemen is not biimplication A<->B. 1. If (i%8==0) then : ((i%4==0)&&(i%2==0)) statement 1 is true. But 2. if ((i%4==0)&&(i%2==0)) then (i%8==0). Statement 2 is incorrect.
6th Nov 2022, 10:13 PM
Oliver Pasaribu
Oliver Pasaribu - avatar
+ 1
Yes, thank you AJ and Brian. I think it is clear now that is two different problem. The sequence is also affrcts it. Yes. (i%8==0) -> ((i%2==0)&&(i%4==0) This is true. But: ((i%2==0)&&(i%4==0) -> (i%8==0). This is incorrect.
6th Nov 2022, 10:30 PM
Oliver Pasaribu
Oliver Pasaribu - avatar
+ 1
Ok.
8th Nov 2022, 12:25 AM
Oliver Pasaribu
Oliver Pasaribu - avatar
0
Of course no. Try with i = 12; the first test will be True whereas the second will be False.
7th Nov 2022, 1:12 AM
Abdelhaq El Amraoui
Abdelhaq El Amraoui - avatar