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From: James Weirich <James.Weirich@sdrc.com>
Subject: Re: Software landmines (loops)
Date: 1998/09/01
Message-ID: <wtk1zpwhv4w.fsf@sdrc.com>#1/1
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Organization: Structural Dynamics Research Corporation
Newsgroups: comp.lang.eiffel,comp.object,comp.software-eng,comp.lang.ada
Date: 1998-09-01T00:00:00+00:00
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    Matthew> Let's once again compare the decision tables.  If we
    Matthew> re-write the code, to put it into Matt-like (because Matt
    Matthew> likes it) syntax:

    Matthew> equal (l,r: LIST): BOOLEAN is
    Matthew>       require
    Matthew>               l /= Void and r /= Void
    Matthew>       do
    Matthew>               if l.count /= r.count then
    Matthew>                  return False
    Matthew>               end
    Matthew>               from
    Matthew>                  l.start; r.start
    Matthew>               until
    Matthew>                  l.off
    Matthew>               loop
    Matthew>                  if l.item /= r.item then
    Matthew>                     return False
    Matthew>                  end
    Matthew>                  l.forth; r.forth
    Matthew>               end
    Matthew>               return True
    Matthew>       end

    Matthew> This version has only two rules in the decision table for
    Matthew> the loop predicate:

    Matthew>        1  2
    Matthew> l.off  T  F

Yes, but you are ignoring the fact that there are now two loop exits.
If you ask the question "When will the loop terminate?", you must
consider all the exits, including the early return.

So instead of a single, 2 entry table, you have two 2-entry tables.
Combining them into a single table will produce the same 4 entry table
as the one you produced for Loryn Jenkins's code.

Seems to me the complexity is about equivalent.

-- 
-- Jim Weirich     jweirich@one.net    http://w3.one.net/~jweirich
---------------------------------------------------------------------
-- "A distributed system is one in which I cannot get something done
-- because a machine I've never heard of is down."   --Leslie Lamport