On Monday, February 11, 2013 11:55:19 PM UTC-6, Chris Angelico wrote:
> On Tue, Feb 12, 2013 at 12:06 PM, 88888 Dihedral wrote:
> > A permanently mutated list is a tuple of constant objects.
>
> I nominate this line as "bemusing head-scratcher of the week".
Actually the statement is fact IF you can grok it through the eyes of clarity.
"A permanently mutated list..."
A list that has been mutated permanently, that is, it cannot be changed back
into a list. psst: i have a sneaking suspicion that he his referring to tuples,
let's see.
"...is a tuple..."
Ha! Well in Python the immutable sequence type /is/ a tuple after all.
"...of constant objects..."
The tuple contains objects, and it's objects will maintain a constant ordering
(relatively in tuple structure) until until the tuple's death.
Your confusion may stem from interpreting "constant" as the CS term
"CONSTANT"[1]; whereby the objects in the tuple are programming CONSTANTS, that
is, unable to change. But in reality, although a tuple (bka:StaticList) cannot
expand to add more objects, or shrink to eject existing objects, the objects
themselves CAN change their own internal state WITHOUT disrupting the immutable
harmony of the tuple.
Observe:
py> class Foo(object):
pass
py> foo = Foo()
py> t = (1,'1', foo)
py> t
(1, '1', <__main__.Foo object at 0x0267BF50>)
py> t[-1].bar = "abc"
py> t
(1, '1', <__main__.Foo object at 0x0267BF50>)
Or by expanding a list
py> t = (1,2,3)
py> t = t+([],)
py> t
(1, 2, 3, [])
py> t[-1].append('circus')
py> t
(1, 2, 3, ['circus'])
[1] Which is an unfortunate side-effect of polysemy and compounded
exponentially by naive (and sometimes a purely malevolent intent when)
transformation of words into esoteric problem domains.
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