Re: [Boost-users] About naming of integer log in base 2

Subject: Re: [Boost-users] About naming of integer log in base 2
From: John Maddock (boost.regex_at_[hidden])
Date: 2010-07-18 04:37:50

>What if I make 2 versions of ilog2:
>
>   - unchecked_ilog2(T value) - don't checks the input value
>   - ilog2(T value) - returns -1 if value == 0 else returns
>   unchecked_ilog2(value)
>
>Following the line of:
>http://www.boost.org/doc/libs/1_43_0/libs/math/doc/sf_and_dist/html/math_toolkit/special/factorials/sf_factorial.html

Maybe, it depends on the relative cost of two: the reason for 
unchecked_factorial is that low-order factorials are often used inside the 
inner loop of a computation, where anything more expensive than a simple 
table lookup is out of the question (and the check can easily be moved 
outside the loop anyway).  Does the same thing apply here.... or is the cost 
of the check trivial compared to the bit manipulations?  I don't know the 
answers to these BTW, just some questions you might want to think about ;-)

ilog2 isn't a bad name BTW, John.