A class question

[Bruno Desthuilliers]

Hrvoje Niksic a écrit :
> Bruno Desthuilliers <bruno.42.desthuilliers at wtf.websiteburo.oops.com>
> writes:
> 
>>> It seems to me that in recent times more Python beginners come from
>>> a Java background than from a C one.
>> Java does have "container" variables for primitive types, and even
>> for "references", Java's variables are more than names - they do
>> hold type informations too. Now I don't pretend to know how this is
>> really implemented, but AFAICT, and at least from a cognitive POV,
>> Java's variables model looks very close to the C/C++ model.
> 
> While Java's variable declarations bear a superficial (syntactical)
> similarity to C, their semantics is in fact equivalent to the
> object-reference semantics we know in Python.   They implicitly refer
> to objects allocated on the heap and, just like in Python, the same
> object can be referenced by multiple variables. 

You're talking about reference types here - not primitive types. And 
even then, from what I remember (not having done any Java these last 4 
years at least), Java's reference types are much closer to C++ 
references than to Python.

> If Java's model were
> close to C/C++, that would not be possible without explicit
> pointers/references

The reference is implicit for non-primitive types.

> since an object would be "contained" by the
> variable.
> 
> Variables holding primitive types don't really influence the
> variable/object relationship, since the values they hold are by nature
> immutable and without identity.

Python's immutable types instances does have an identity, and follow the 
same rules as mutable types instances - mutability set aside of course. 
Which is not the case with Java, where primitive types and reference 
types follow distinct rules. I'll check this out (not having done Java 
for a couple years) and come back, but I certainly remember Java's model 
as being way closer to C++ than to Python.