Paul Rubin wrote:
That only goes so far though. Suppose instead of complex numbers
you want to sort expressions, like:
a(b,c(d,e),f(g,h))
treat those as parse trees in the obvious way.
Presuming that a, c, and f are function calls that return Tree
instances, you give Tree a __lt__ member that does what you say below.
You want to compare on
the root, and if the roots are equal, compare the left subtree, then
the right subtree, etc.
> Do you REALLY want to sort over and over
all the way to the max depth of all the trees?
Don't understand this.
I don't understand what the purpose of was of getting rid of the cmp
arg.
Cmp requires a 3-way classification. Sorting only requires 2-way.
cmp was called nlogn times, key n times.
cmp in practical use amounted to calling some key function on both
items, so cmp amounted to 2*n*log(n) key calls pluse extra overhead.
Another thing that apparently broke was tuple destructuring in
function args. You can no longer say
def first((a,b)): return a
def second((a,b)): return b
make getters for the first and second elements of a tuple. Sure, you
could use operator.itemgetter for that example, but often you want to
parse out more complicated nested tuples. I do that all the time with
Python 2.5 (typically in conjunction with itertools.groupby) but
if/when I downgrade to 3.0, a bunch of my code is going to break.
Do your tuple destructuring in the first statement in your body and
nothing will break. Don't upgrade until it is an upgrade for *you*.
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