[Bro-Dev] set and vector operators

[Johanna Amann]

> (3) Implement "v += e" to mean "append the element e to the vector v".

Do we want to do this now, or should we potentially wait a release-cycle
with it (to prevent the situation where v + e and v+= e means something
different).

Looking at the emails I am generally not 100% sure if we reached consensus
on this one.

> (4) Wait on whether "v + e" should mean "return a vector that is v with
>     the element e appended".  (And indeed we can't do this right now if
>     we're #2.)

Yup.

> I'm not clear whether we reached agreement on:
> 
> (7?) Add "s1 &= s2" etc. to mean "s1 = s1 & s2".  The advantage of
>      having this as an operator is it might more easily enable efficient
>      implementation of some set operations for big sets.  I suppose
>      if we have it then we'd be expected to also have:
> 	(7') "c1 &= c2" etc., i.e., bitwise assignments for "count"
> 	     variables.

They were contained in the "minimal" list that Jon came up with. I think I
would be ok with them, but they did not really get any discussion
afterwards that I can see.

Johanna