Finding the instance reference of an object

Marc 'BlackJack' Rintsch bj_666 at gmx.net
Tue Nov 4 01:27:31 CET 2008


On Mon, 03 Nov 2008 15:27:01 -0700, Joe Strout wrote:

> On Nov 3, 2008, at 2:36 PM, Aaron Brady wrote:
>> Python can do the swap operation on mutable types, for example.
> 
> That's in the "no fair" category.  C can do a swap operation on mutable
> types, too, though it also has only pass-by-value.  Same for Java, or
> for REALbasic or VB.NET using "ByVal" mode.  The fact that you can
> mutate mutable types has absolutely nothing to do with whether the
> parameter was passed by reference or value.  If was by reference, you
> can change it (the parameter itself, not something the parameter may
> refer to).  If it's by value, you can't.
> 
> In Python, you can't.  That's because parameters are passed by value.

This conclusion is flawed because call-by-value is not the only parameter 
passing style with that characteristics.

>> By-Value and By-Reference are not the only passing methods.  True or
>> False?
> 
> True, but the others are rarely used and don't apply to any of the
> languages we've been discussing.

Maybe this is a surprise for you, because we haven't discussed this in 
much detail in this group lately, but it applies to Python which does 
call-by-object or call-by-sharing.  ;-)

Ciao,
	Marc 'BlackJack' Rintsch



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