On Thu, 13 Mar 2008 08:54:43 +0000, Paul Rudin wrote:
>> Whatever python has for a calling convention, it is close enough that
>> naming it "call by reference" gives people a reasonable idea of what is
>> going on.
>
> Quite. The thing is not to get hung up with the label - but to
> understand what actually happens.
Agreed. And I think the best way to do that is to use the same terms that
other languages use to get very different behaviour indeed.
"Python is call by reference, but this doesn't work like call by
reference in all the other languages I've used:
def negate(n):
n = -n
x = 2
negate(x)
assert x == -2
Is this a bug, or is Python actually call by value?"
And now comes the explanations that Python is actually call by value, but
the values being copied are *pointers* (ignoring Jython, IronPython and
PyPy); or that Python is really call by reference, but different
"things" (it's never quite clear what exactly) happen depending on
whether the arguments are mutable or immutable; or that if you define
reference broadly enough, everything is a reference; or that if you
define value broadly enough, everything is a value; or if schools would
just stop teaching kiddies C and start teaching them Lisp, call by
reference semantics would be understood in a different way, or or or or...
And thus, by insisting that there are two and only two calling
conventions, no matter how many different kinds of calling behaviour
actually exist, we ensure that we'll be having this same *&$%^*# argument
when Python 4000 comes out.
And for that we can all be grateful.
--
Steven
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