Re: new module 'popcount'

[Matthew Woehlke]

Ben Pfaff wrote:
> The name 'popcount' is not perfect, but it is a well-known name
> for this function.  That is what it is called by, e.g., GCC,
> Wikipedia, and _Hacker's Delight_.

Actually Wikipedia "popcount" and "population count" redirect to 
"Hamming weight" :-).

> I don't see why anyone would have trouble understanding
> population count, unless an opaque, uncommented implementation
> made it necessary to reverse-engineer the calculation.

My first reaction to "popcount" is 'something to do with stacks'. My 
first reaction to "population count" is 'ytf do we have census code in 
gnulib?!'.

My first reaction to "Hamming weight" is 'hmm, sounds familiar and 
useful, like something with a legitimate place in gnulib'.

Obviously I'm not very familiar with use of such a function, but should 
that be relevant? The name "popcount" is only meaningful if you already 
are familiar with the function, otherwise it leaves you wondering what 
it is and why it's in gnulib. The name "Hamming weight" seems more 
likely to be recognized, if only in the 'feels like I heard about that 
once' sense, by average programmers.

> I do agree that 'hamming_weight' is a precise name for this
> function.  But it is not a descriptive name: one must know by
> rote what a Hamming weight is.  I think that "population count"
> is far more logical.

I probably learned what a "Hamming weight" was at some point (sure seems 
like I did, anyway). However, I can't say I'd ever heard of "population 
count" until this thread. Therefore I think the above argument is 
invalid, "population count" is no less obscure than "Hamming weight" in 
my opinion (i.e. I would say "one must know by rote" about both).

Here's another exercise: ;-)
http://www.google.com/search?hl=en&q=%22population+count%22&btnG=Search
http://www.google.com/search?hl=en&q=%22hamming+weight%22&btnG=Search

I would have to say that gcc using the name is the biggest (and possibly 
only) argument for "popcount".

--
Matthew
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