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shift operators.. again

 
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just when I'm starting to feel confortable with shifting, there's my friend Dan with his excellent questions... :roll:

What is the result of attempting to compile and run the above program?
a. Prints: -4
b. Prints: -3
c. Prints: -2
d. Prints: 0
e. Prints: 1
f. Prints: 127
g. Prints: 508
h. Runtime Exception
i. Compiler Error
j. None of the Above
It prints -4. I reached til 508, but now this 508 int value has to be chopped off to fit in a byte, right? How do you guys do that?..
 
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Hi Andres
You cannot consider this way, you must consider it as 8 bit number and the digits that go out from the left are lost. Then if the leftmost bit is 1 that means it is a negative number so you must calculate the two's complement of the number.

Hope that Helps
[ June 29, 2003: Message edited by: Alexan Kahkejian ]
 
Andres Gonzalez
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Thanks Alexan. What I usually do is the following:
x >> n = x / 2^n
x << n = x * 2^n
and that's it. Using this formula I got 508. So from this number, I didn't know how to "make it fit" into a byte.
 
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b <<= 2 is the same as b = (byte)(b << 2)
except that b is evaluated only once.
Let�s evaluate this expression: (byte)(b << 2)
First the left operand b is promoted to type int.
01111111 is promoted to 0000 0000 0000 0000 0000 0000 0111 1111
Then the left shift operation << is performed.
0000 0000 0000 0000 0000 0001 1111 1100 (== 508)
Then the result is converted from type int to type byte by
discarding all but the 8 lowest order bits.
11111100 (== -4)
[ June 29, 2003: Message edited by: Marlene Miller ]
 
Marlene Miller
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b = b << 2; //compiler error, must be cast to type byte
b <<= 2; //implicit cast to type byte
In both of these examples, the value of b is promoted to an int before << is performed.
 
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I think we need to do like this.. keep subtracting 128 from 508 till you get a nearest value to -128 in range (-128 & 127). Can anyone confirm whether this is correct way?
Thanks,
Prasad
 
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