[selectors4] Specificity in base 256

Hi,

Selectors specificity is calculated from three integers a, b and c and:

> Concatenating the three numbers a-b-c (in a number system with a
> large base) gives the specificity.

My understanding is that "a large base" means one larger than any of a, 
b and c. In other words, the final specificity is not a single number 
but a tuple of 3 integers, compared in lexicographic order.

Apparently, "a large base" is 256 in Gecko and WebKit:

http://stackoverflow.com/questions/2809024/points-in-css-specificity/11934505#11934505
http://news.ycombinator.com/item?id=4388649

I’m not sure about other engines.

Should the spec be made more precise on this point? Is it deliberately 
vague to allow this kind of behavior? (Using a single int is probably 
more efficient.)

In my opinion, the behavior in Gecko and WebKit is incorrect but the 
approximation is good enough. I don’t know if this makes a difference in 
any real stylesheet (ie. not made for the purpose of experimenting with 
specificity.)

To keep a single integer but be more correct (IMO), implementation could 
also clamp b and c to a maximum like 255 rather than letting them overflow.

-- 
Simon Sapin