Grant Edwards <invalid@invalid.invalid>:
>> Anyway, I would say Python definitely is in the classic pass-by-value
>> camp. Here's a simple test:
>>
>> def f(x):
>> x = 3
>>
>> y = 1
>> f(y)
>> print(y)
>>
>> If it prints 1, it's pass by value. If it prints 3, it's pass by
>> reference.
>
> Somebody else might just as honestly say that it's pass by reference:
Yes, but that would be a shift from the 1970's notion:
In pass-by-value, the actual parameter is evaluated. The value of the
actual parameter is then stored in a new location allocated for the
function parameter.
[...]
In pass-by-reference, the actual parameter must have an L-value. The
L-value of the actual parameter is then bound to the formal
parameter.
[...]
* A parameter in Pascal is normally passed by value. It is passed by
reference, however, if the keyword var appears before the
declaration of the formal parameter.
procedure proc(in: Integer; var out: Real);
* The only parameter-passing method in C is call-by-value; however,
the effect of call-by-reference can be achieved using pointers. In
C++ true call-by-reference is available using reference parameters.
<URL: http://www.cl.cam.ac.uk/teaching/0910/ConceptsPL/Algol-Pasca
l.pdf>
Pass by reference could easily be added to Python, too, if that were
deemed useful.
Marko
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