This case can arise when the last occurence of a word is removed, or
when a lexicon is shared across multiple indexes.

XXX Not sure this code is correct, but it might be and the tests pass.
If it's wrong, we need more tests.

internals.

testStopWords().  That isn't the real point.  The real point is to
fiddle the scaffolding enough to make it possible to run a white box
test of the Okapi indexer too.  That isn't here yet.

with the docid is greater than 0 too.

and the Okapi indexer.  testZCTextIndex was, and remains, strongly tied
to the cosine indexer.

reinitializing to the global Index even if that wasn't how the object
was constructed.

It prints the the results and a summary of the times for the last 10
of 11 trials.

Otherwise, there's no way to report the total number of matches from
which the nbest were selected.

I changed all the functional tests that I knew how to fix, but not the
mhindex stuff.  All unit tests pass.

Removed QueryParser as a persistent attribute of the ZCTextIndex so that
it doesn't need to be persistent (It stores no state).

Updated tests. Functionally tested in Zope.

indexed (where the bytes are counted before entry into the pipeline,
and the words are counted after the pipeline is done).  To get the
numbers, use the _nbytes and _nwords instance variables directly.

(unless I erred ...).

intersection gimmicks into their own functions with their own test suite.

This turned up two bugs:

1. The mass weighted union gimmick was incorrect when passed a list with
   a single mapping.  In that case, it neglected to multiply the mapping
   by the given weight.

2. The underlying weighted{Intersection, Union} code does something crazy
   if you pass it weights less than 0.  I had vaguely hoped to be able
   to subtract scores by passing 1 and -1 as weights, but this doesn't
   work.  It's hard to say exactly what it does then.  The line
       weightedUnion(IIBTree(), mapping, 1, -2)
   seems to return a mapping with the same keys, but *all* of whose
   values are -2, regardless of the original mapping's values.

www.python.org.

next step is to add queries using ZCTextIndex

A little overzealous in the last checkin.

ZCTextIndex has grown a new argument with a default value that can be
used to specify an Index class to use.  The default is OkapiIndex.Index.

There is a little kludge to make the test succeed.
testZCTestIndex.IndexTests uses the Index.Index tests instead of
OkapiIndex.Index.  Tim will probably fix this.

names.

Re-order imports so that all Zope imports go together and are separate
from all the ZCTextIndex imports.

Reformat _apply_index() doc string to use std Python style, which is
one-line summary followed by paragraphs of text that start at the same
offset as the function name.

Do comparison of None using is instead of ==.