Terry Reedy wrote:
...
Your point, that taking floor(log2(x)) is redundant, is a good catch.
However, you should have added 'untested' ;-). When value has more
significant bits than the fp mantissa can hold, this expression can be 1
off (but no more, I assume). The following correction should be
sufficient:
res = math.frexp(value)[1] - EXP_OF_ONE
test = 1<<res
if test > r: res -= 1
elif 2*test < r: res += 1
Well, I did test, but poorly.
>>> high_bit(1<<587)
587
>>> high_bit(1<<587-1)
586
And of course, I _should_ have tested
>>> high_bit((1<<587)-1)
587
By the way, I wrote my response before any replies had happened; it was
not a correction to your post.
--Scott David Daniels
[EMAIL PROTECTED]
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