How does bitshift work?

3 vues (au cours des 30 derniers jours)
Kaavya N
Kaavya N le 4 Mai 2021
bitshift(56,-1)
gives answer 28 in matlab
My understanding of this working is as follows:
the function converts 56 to binary value ie 0101 0110 and does right shift since its -1
so 0010 1011 -> 2b (hexa)
so the answer should be "2b" right?
How does this function work?
  4 commentaires
Stephen23
Stephen23 le 5 Mai 2021
Modifié(e) : Stephen23 le 5 Mai 2021
"the function converts 56 to binary value ie 0101 0110"
You appear to have mixed up decimal and hexadecimal:
B = '01010110'; % your binary string
D = pow2(numel(B)-1:-1:0)*sscanf(B,'%1d') % decimal
D = 86
D = bin2dec(B) % decimal
D = 86
H = dec2hex(D) % hexadecimal
H = '56'
H = sprintf('%x',D) % hexadecimal
H = '56'
Kaavya N
Kaavya N le 5 Mai 2021
Thank you

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Walter Roberson
Walter Roberson le 4 Mai 2021
dec2bin(56,8)
ans = '00111000'
In other words, your difficulty is that 0101 0110 is not the correct representation for 56.
  3 commentaires
Walter Roberson
Walter Roberson le 5 Mai 2021
Consider for a moment that 56 decimal can be divided by 2 to get 28, and then divided by 2 again to get 14, and then divided by 2 again to get 7, but that cannot be divided by 2. That is three divisions, so the binary representation must end in three 0's.
Scott MacKenzie
Scott MacKenzie le 5 Mai 2021
It's also worth noting that with each division-by-two the remainder (0 or 1) becomes part of the binary result. The first remainder is the bit on the right (the least-significant bit). Each successive remainder is appended on the left. The following figure might help. It shows the conversion from decimal 26 to the binary equivalent, 11010.

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