RE: Bitflags

[John Mckenna <jmckenna@...>]

Alex Bilyk writes:

>> 'flags = FOO_BLUEPANTS + FOO_3PLANES + FOO_EDIBLE' ?

>This will result in totally unreadable/misinterpreted code, IMHO. The
>assumption that '+' can somehow intuitively be realted to '|' is ungrounded
>to say the least.

On the "all programming languages look like C" planet, perhaps.  For the
rest of us, the use of | for a set union operator is totally baffling.

My first choice would be the standard mathematical symbols.  But that
requires Unicode - maybe the industry will have got its act together in ten
years or so.  I want to be able to type these things easily.

My second choice: + for union, - for difference (A - B is the members of A
that are not members of B), and * for intersection.  The empty set is nil.
Then you can say

FOO_ALL = FOO_BLUEPANTS + FOO_3PLANES + FOO_EDIBLE + FOO_WOBBLY + FOO_ALIEN
if flags * (FOO_ALL - FOO_EDIBLE) then
end

I believe this can be implemented in pure Lua, or with C helper functions
for speed.  Certainly no changes to the core language are required.
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