Re: [nimh-dev] More stuff

[Tom Plagge <tplagge@xxxxxxxxxxxxxxxxx>]

> Thus spake "Jon Stewart":
> > > 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 negatio
> n,
> > > though. Say I want to list all messages in foo and bar, e.g., I should be
> > > able to 'scan foo&bar'.

As opposed to scan foo ; scan 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.

I can think of a pythony simple way to do this.  Say you specified a sequence
"cur 8 9-11 foo" where foo is an existing sequence consisting of "7 10-12", and
cur is 4.

1. ['cur', 8, '9-11', 'foo']    <-- split by whitespace
2. [4, 8, '9-11', [7, '10-12']]  <-- parse tokens (foo, cur)
3. [4, 8, [9, 11], [7, [10, 12]]]  <-- parse ranges 
4. [4, 8, [9, 11], 7, [10, 12]]  <-- eliminate sublists
5. [4, 8, [9, 11], 7, 12]  <-- eliminate overlap
6. [4, 7, 8, [9, 11], 12] <--  sort

Then 5. would be the final form that was stored in sequence.seq.  No need to
wrap up [7, 8, [9,11], 12] into [7,12]; it's plenty easy to deal with in its
current form.  For step 3, you'd have to take a piecewise continuous range
and split it up into continuous ranges; for instance, if your folder contains
messages 1-400 and 402-500, and you specify 1-500, it should store the value
[[1,400],[402,500]]

________________________________________________________________________

Tom Plagge                              UC Berkeley Physics Dept.
351 LeConte Hall                        Voice: (510) 643-1650
Berkeley, CA  94720                     Email: tplagge@xxxxxxxxxxxxxxxxx
________________________________________________________________________

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