# shift operators

Anonymous
Ranch Hand
Posts: 18944
how do we evaluate -1>>-1. The o/p : -1.Is there any rule
that -ve no >>-1 is -1.
Thanks!

William Brogden
Author and all-around good cowpoke
Rancher
Posts: 13074
6
As I recall, the shift operator ignores the sign. For a 32 bit shift, it masks off the low 5 bits and uses that value, for that reason, a shift of 33 is the same as a shift of one.
Masking the low five bits of -1 gives you 11111 = 31 places shifted.
Shift of long (64 bit) values masks off the low 6 bits.
Bill

Anonymous
Ranch Hand
Posts: 18944
But can we shift by -1...what is the rule regarding -ve shift of a number...whether +ve or -ve?

mita
Ranch Hand
Posts: 50
how do we evaluate -1>>-1. The o/p : -1.Is there any rule
that -ve no >>-1 is -1.
Thanks!
shifting by -1, is equivalent to shifting by 31.(-1 + 32 = 31).
So -1 >> -1 equivalent to -1 >> 31 .The result is -1.
When we do shifting by -ve numbers, for a 32bit we add 32 to the negative number & add 64 in case of 64 bits.
Hope it helps.