Wireshark-bugs: [Wireshark-bugs] [Bug 11860] Display filter operator != not working as exepected

Date: Thu, 17 Dec 2015 01:33:03 +0000

Comment # 14 on bug 11860 from
(In reply to Guy Harris from comment #12)
> (In reply to João Valverde from comment #9)
> > I was suggesting to implement the operators differently: '==' implies OR and
> > '!=' implies AND. Does that make sense?
> 
> And what do '>', '>=', '<', and '<=' imply?

This seems more clearcut to me. I think the only meaningful definition of '<'
is ip.addr < x <=> (ip.src < x AND ip.dst < x). But this does not say anything
about equality (willing to be proved wrong).

ip.addr is shorthand for the cartesian product of {ip.src}x{ip.dst}. The only
total ordering defined on the (2-dimensional) plane is lexicographical
ordering.

If you define the '<' relation as: ip.addr < x <=> (ip.src < x OR ip.dst < x)

then antisymmetry breaks.

a = (1,3); b = (2,2)

a <= b TRUE [a1 < b1]
b <= a TRUE [b2 < a2]
a == b FALSE [a1 != b1, a2 != b2]


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