logical Operators in C#

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hi The under code should return 15 but in C# return value is 14 !!!
why in C# return value is 14

C#

int x = 2;
int y =x+ 4* ++x;
MessageBox.Show(x.ToString()+"\n"+y.ToString());

Posted 23-Oct-11 6:27am

f.zeinali

Updated 23-Oct-11 6:29am

Mehdi Gholam

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Sergey Alexandrovich Kryukov 23-Oct-11 23:25pm

Where is a logical operator?!
--SA

4 solutions

Solution 1

14 is correct

For the left x=2 + 4 * (increment x =3) -> 2+ 4*3 -> 14

Posted 23-Oct-11 6:31am

Mehdi Gholam

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Abhinav S 23-Oct-11 12:34pm

Solution 5

Mehdi and Abhinav are correct.
The result is also 14 in Java.
It is identical to y = x + 4 * (x+=1);

The expressions are evaluated left to right.
You will get 15 if the left x is moved to the right, y = 4 * ++x + x;

Posted 23-Oct-11 8:50am

Ray Radin

Comments

Sergey Alexandrovich Kryukov 23-Oct-11 23:24pm

Finally, an answer with some explanation, my 5.
--SA

Solution 3

No The left x in line two is 3
This code in java return value is 15

Posted 23-Oct-11 6:35am

f.zeinali

Comments

Mehdi Gholam 23-Oct-11 12:36pm

Use the comments if you need further assistance, don't post answers.

f.zeinali 23-Oct-11 12:45pm

plz run this code
<pre lang="c#">
int x = 2;
int y = ++x;
MessageBox.Show(x.ToString()+"\n"+y.ToString());
</pre>
The result is
x=3
y=3

Mehdi Gholam 23-Oct-11 12:38pm

I doubt that, all operation are done from the left unless you have '(', to get 15 use x+(4*++x)

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Abhinav S · Accepted Answer · 2011-10-23T06:32:00

Solution 2

int y =x+ 4* ++x;
This can be simplified to y = x + 4 * (x+1).

++x is a prefix unary operator. So the 1 is first added and then it used for further calculation.
As a result expression becomes 2 + 4 * (2 + 1) and hence 14.

Posted 23-Oct-11 6:32am

Abhinav S

Comments

Mehdi Gholam 23-Oct-11 12:35pm

my 5!

Abhinav S 23-Oct-11 12:36pm

Thank you.

Espen Harlinn 23-Oct-11 18:01pm

Right :)

Abhinav S 24-Oct-11 1:13am

Thanks.

BillWoodruff 24-Oct-11 0:22am

Spot on Abhhinav-ji ! It is interesting to me that looking at this expression my mind somehow wants to imagine that the unary ++ prefix operator gets precedence and then modifies the value of the 'x variable at the start: but the moment I think of the compiler as stuffing the value of the first 'x in a register, reality comes back into 'focus.'

How have I missed being aware of ++ used as as a prefix ? :) ... duh ...