I found where rich comparison of unequal recursive objects gave
unintuituve results. In a discussion with Tim, where we discovered
that our intuition on when a<=b should be true was failing, we decided
to outlaw ordering comparisons on recursive objects. (Once we have
fixed our intuition and designed a matching algorithm that's practical
and reasonable to implement, we can allow such orderings again.)
- Refactored the recursive-object comparison framework; more is now
done in the support routines so less needs to be done in the calling
routines (even at the expense of slowing it down a bit -- this
should normally never be invoked, it's mostly just there to avoid
blowing up the interpreter).
- Changed the framework so that the comparison operator used is also
stored. (The dictionary now stores triples (v, w, op) instead of
pairs (v, w).)
- Changed the nesting limit to a more reasonable small 20; this only
slows down comparisons of very deeply nested objects (unlikely to
occur in practice), while speeding up comparisons of recursive
objects (previously, this would first waste time and space on 500
nested comparisons before it would start detecting recursion).
- Changed rich comparisons for recursive objects to raise a ValueError
exception when recursion is detected for ordering oprators (<, <=,
>, >=).
Unrelated change:
- Moved PyObject_Unicode() to just under PyObject_Str(), where it
belongs. MAL's patch must've inserted in a random spot between two
functions in the file -- between two helpers for rich comparison...
wraps to 80chars, and adds some really hacky setting of compiler
options when CC and LDSHARED are given on the make command line.
(The Distutils should probably provide a utility function to
automatically handle a number of common environment variables)
Check additional include directories for SSL
Don't build modules that are linked into the Python binary statically
Factored out the detection of Tkinter out into a method, since it's
the most complicated module to set up
Simplify the logic for detecting Tkinter
- Changed description of rich comparisons to emphasize that < and >
(etc.) are each other's reflection. Also use this word in the note
about the demise of __rcmp__.
exceptions when compared using <, <=, > or >=.
NOTE: This is a tentative change: this means that cmp() involving
complex numbers will raise an exception when the numbers differ, and
that in turn means that e.g. dictionaries and certain other compounds
(e.g. UserLists) containing complex numbers can't be compared either.
So we'll have to decide whether this is acceptable. The alpha test
cycle is a good time to keep an eye on this!
- In count(), remove(), index(): call RichCompare(Py_EQ).
- Get rid of array_compare(), in favor of new array_richcompare() (a
near clone of list_compare()).
- Aligned items in array_methods initializer and comments for type
struct initializer.
- Folded a few long lines.
- Use PyObject_RichCompareBool() when comparing keys; this makes the
error handling cleaner.
- There were two implementations for dictionary comparison, an old one
(#ifdef'ed out) and a new one. Got rid of the old one, which was
abandoned years ago.
- In the characterize() function, part of dictionary comparison, use
PyObject_RichCompareBool() to compare keys and values instead. But
continue to use PyObject_Compare() for comparing the final
(deciding) elements.
- Align the comments in the type struct initializer.
Note: I don't implement rich comparison for dictionaries -- there
doesn't seem to be much to be gained. (The existing comparison
already decides that shorter dicts are always smaller than longer
dicts.)
- tuplecontains(): call RichCompare(Py_EQ).
- Get rid of tuplecompare(), in favor of new tuplerichcompare() (a
clone of list_compare()).
- Aligned the comments for large struct initializers.
earlier coercion changes, not by rich comparisons. When a coercion
function returns 1 (meaning it cannot do it), it should not INCREF the
arguments. When no __coerce__() method was found, instance_coerce()
originally returned 0, pretending it did it. Neil changed the return
value to 1, more accurately reflecting that it didn't do anything, but
forgot to take out the two INCREF calls.
- sort's docompare() calls RichCompare(Py_LT).
- list_contains(), list_index(), listcount(), listremove() call
RichCompare(Py_EQ).
- Get rid of list_compare(), in favor of new list_richcompare(). The
latter does some nice shortcuts, like when == or != is requested, it
first compares the lengths for trivial accept/reject. Then it goes
over the items until it finds an index where the items differe; then
it does more shortcut magic to minimize the number of additional
comparisons.
- Aligned the comments for large struct initializers.
- Use the compare nesting level and in-progress dictionary properly in
PyObject_RichCompare().
- Change the in-progress code to use static variables instead of
globals (both the nesting level and the key for the thread dict were
globals but have no reason to be globals; the key can even be a
function-static variable in get_inprogress_dict()).
- Rewrote try_rich_to_3way_compare() to benefit from the similarity of
the three cases, making it table-driven.
- In try_rich_to_3way_compare(), test for EQ before LT and GT. This
turns out essential when comparing recursive UserList instances;
with the old code, these would recurse into rich comparison three
times for each nesting level up to NESTING_LIMIT/2, making the total
number of calls in the order of 3**(NESTING_LIMIT/2)!
NOTE: I'm not 100% comfortable with this. It works for the standard
test suite (which compares a few trivial recursive data structures
only), but I'm not sure that the in-progress dictionary is used
properly by the rich comparison code. Jeremy suggested that maybe the
operation should be included in the dict. Currently I presume that
objects in the dict are equal unless proven otherwise, and I set the
outcome for the rich comparison accordingly: true for operators EQ,
LE, GE, and false for the other three. But Jeremy seems to think that
there may be counter-examples where this doesn't do the right thing.
Guido van Rossum
Andrew M. Kuchling
Tim Peters
Fred Drake
Skip Montanaro
Ka-Ping Yee
Neil Schemenauer
Fredrik Lundh