Re: [nimh-dev] More stuff

["Jon Stewart" <stew1@xxxxxxxxxxx>]

> MH treats sequences like sets. E.g. 'scan 2 1 1' will show you the scan
> for 1, followed by the scan for 2. I like it that way. I wish it were
> also a way to apply set-theoretic operations other than union and negation,
> though. Say I want to list all messages in foo and bar, e.g., I should be
> able to 'scan foo&bar'.


Hmm. Then I guess we will need to calculate the sequence upfront. In that 
case, it's probably best to have a sorted list of range tuples, [beg, 
end). Constructing the list isn't too hard. You throw the first specified 
range in the list and, if there are any others, you go through the list 
for each one (it's a quadratic algorithm) and either insert the range in 
its rightful place -- if it's disjoint with existing ranges -- or expand 
the existing ranges if there are overlaps.

CPU and memory usage are constant in the common case of only one specified 
range. If someone is dumb enough to specify such a complicated listing 
that the quadratic nature gets to be inhibiting, well, that's a good 
thing. Software should stand up for itself when abused.


Jon
-- 
Jon Stewart                                 Advanced Los Angeles C++
stew1@xxxxxxxxxxx                           http://www.alacpp.org
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