On 2/15/13 1:29 PM, Dan Drake wrote:
This seems weird to me:
sage: (-10).bits()
[0, -1, 0, -1]
It makes it look like binary now includes -1 along with 0 and 1, making
it..ternary?
I guess that the bits() function is supposed to satisfy
x == sum(b*2^e for e, b in enumerate(x.bits()))
...but you have to interpret b as a regular integer -- and not a bit --
for that to be true, since -1 equals 1 in the integers mod 2. And
indeed, the parent of all the "bits" is the Integer Ring and not GF(2)
or Integers(2).
At the very least, I think this deserves a note in the bits()
documentation. Or, what might be less popular, a change to bits() to
somehow return a sign -- maybe a tuple (sign, [list of bits])?
Thoughts?
FYI, here's what python does:
>>> bin(-10)
'-0b1010'
Jason
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