+ 2

Why output is 16 instead of 15??

#include<stdio.h> main() { int a=6; int b=++a + ++a; printf("%d",b); }

21st May 2017, 9:06 PM
sazzad hossain rafi
sazzad hossain rafi - avatar
14 Réponses
+ 8
the prefix (++a) operators takes precedence, so a is incremented twice, then the new value of a is added twice to 8 + 8
21st May 2017, 9:19 PM
Burey
Burey - avatar
+ 2
int a = 6 b = ++a + ++a b = 7+1 + ++a b = 7+1 + 7+1 b = 8 + 8 b = 16 @sazzad Your second example: ++a + ++a + ++a From previous we know: 8 + 8 + ++a = 16 + ++a = 16 + 9 = 25 The a isn't always valued first in c++.
21st May 2017, 9:35 PM
Rrestoring faith
Rrestoring faith - avatar
+ 2
The solution is in this line: int b=++a + ++a; First ++a makes “a” to 7 before the operand will be evaluated. Second ++ grows “a” in the second operand to 8. When the summation is runing, the “a” is 8. 8 + 8 is 16 ------------------ In Java or PHP the operands evaluated before next operand, so there is the output is 15: public class Program { public static void main(String[] args) { int a=6; int b=++a + ++a; System.out.println( b ); } } ---------- <?php $a=6; $b=++$a + ++$a; printf("%d",$b); ?>
21st May 2017, 9:40 PM
Károly György Tamás
Károly György Tamás - avatar
+ 1
Interesting. To be honest I can't explain how it works, but I think you already knew the answer. The a is incremented twice before it calculate the b.
21st May 2017, 9:09 PM
Chandra Wibowo
Chandra Wibowo - avatar
+ 1
I tried it in C# and it give me 15. Tamás' explanation is right. Different language give different result.
21st May 2017, 9:40 PM
Chandra Wibowo
Chandra Wibowo - avatar
0
Hi, int b=++a + ++a; a is increasing twice before the sum demonstration: b = a + a; =>b=12 b = ++a + a; =>b=14 because a=7 after increase
21st May 2017, 9:20 PM
MBZH31
MBZH31 - avatar
0
@Buray According to your reply won't this code show 27???? why 24? #include<stdio.h> main() { int a=6; int b=++a + ++a + ++a; printf("%d",b); }
21st May 2017, 9:23 PM
sazzad hossain rafi
sazzad hossain rafi - avatar
0
@Tamas According to your reply won't this code show 27???? why 24? #include<stdio.h> main() { int a=6; int b=++a + ++a + ++a; printf("%d",b); }
21st May 2017, 9:28 PM
sazzad hossain rafi
sazzad hossain rafi - avatar
0
@Faith But,it is showing 24 in online compiler not 25
21st May 2017, 9:43 PM
sazzad hossain rafi
sazzad hossain rafi - avatar
0
@Tamas Why are you forcing to use parentheses in your own way??Why not ++a + (++a + ++a).My actual question is why it's showing 24??(You dictated that it shows 25.How??If you explain plz,I will be obliged a lot) 😊😊
21st May 2017, 9:57 PM
sazzad hossain rafi
sazzad hossain rafi - avatar
0
for me the result must be 25 because operation is execute by even (pair) b=++a + ++a + ++a; is like as b=(++a + ++a) + ++a; so ++a + ++a = 16 b=16 + ++a = 16 + 9 = 25
21st May 2017, 9:59 PM
MBZH31
MBZH31 - avatar
0
@Tamaj @MBZH31 ok,I got 25!!!thanks
21st May 2017, 10:11 PM
sazzad hossain rafi
sazzad hossain rafi - avatar
0
In your longer code… int b=++a + ++a + ++a; Use parentheses for understand… int b=(++a + ++a) + ++a; For second + operator the oprerands are “(++a + ++a)” and “++a”. ------------------- Update: The operations evaluated from left to right (except assignment). The 24 is wrong, this code puts 25 in this way: int b=++a + ++a + ++a; 1. first “++a” set “a” to 7 2. second “++a” set “a” to 8 3. first + operator works, so the second + operator gets the left operand as 16 4. third “++a” set “a” to 9 5. second + operator works, so 16 + 9 = 25
21st May 2017, 10:14 PM
Károly György Tamás
Károly György Tamás - avatar