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code explanation

ten doeschate
Greenhorn

Joined: Jun 22, 2013
Posts: 16

in this
what does >>= stand for
drac yang
Ranch Hand

Joined: Apr 19, 2013
Posts: 61
that's compound operator for signed right shift. it's bitwise operator

x >>= 5; means move rightward 5 bits in the unsigned way(only zero would be moved in from the leftmost bit)



this is its unsigned counterpart, >>>=


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Satheesh chandragupthan
Greenhorn

Joined: Jul 05, 2013
Posts: 4
take look on the below explanation please..

value >> num

Here, num specifies the number of positions to right-shift the value in value. That is, the >> moves all of the bits in the specified value to the right the number of bit positions specified by num. The following code fragment shifts the value 32 to the right by two positions, resulting in a being set to 8:

int a = 32;
a = a >> 2; // a now contains 8

When a value has bits that are "shifted off," those bits are lost. For example, the next code fragment shifts the value 35 to the right two positions, which causes the two low order bits to be lost, resulting again in a being set to 8.
int a = 35;
a = a >> 2; // a still contains 8

Looking at the same operation in binary shows more clearly how this happens:

00100011 35
>> 2
00001000 8


Winston Gutkowski
Bartender

Joined: Mar 17, 2011
Posts: 8008
    
  22

drac yang wrote:x >>= 5; means move rightward 5 bits in the unsigned way(only zero would be moved in from the leftmost bit)

<nitpick>
Actually, that's wrong. It's the signed shift, so the sign bit will be moved in regardless of its value.
</nitpick>

You actually go on to show the unsigned version, so I'm not sure if this was a misprint or not.

Winston

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Ramesh Pramuditha Rathnayake
Ranch Hand

Joined: Oct 31, 2012
Posts: 175
    
    1

ten doeschate wrote:
in this
what does >>= stand for


Here 'actual bit size' means, the minimum number of bits need to express the number in binary form.

Think base=2 and exp=5. Then the value is 2*2*2*2*2.
But the actual bit size of exp is 3 (bits- 101). When it is decreased by one first bit is canceled and zero is added to the beginning.(As exp must be>=0). If clause is run only 3 times.
Therefore, if there is no 'if clause', result is 2*2*2.

But the last bit of exp will be 1 two times. Therefore if clause is run twice. Therefore final answer is 2*2*2*2*2

Actually, use of >> here is to decrease bit size by one..


Ramesh-X
 
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