dynamic classes and duck typing

[Walter Bright]

Leandro Lucarella wrote:
> It looks like you can (not as easily) according to bearophile example, but
> this is besides the point, you only want to use malloc() for performance
> reasons, and I already said that D is better than Python on that.
> I mentioned ctypes just for the point of easy C-interoperability.

To me C interoperability means being able to connect with any C 
function. That means handling pointers, structs, etc.


>>> It's simpler, because you only have one obvious way to do things,
>> No, Python has try/catch/finally as well.
> I said *obvious*. try/catch/finally is there for another reason (managing
> errors, not doing RAII). Of course you can find convoluted ways to do
> anything in Python as with any other language.

try/catch/finally is usually used for handling RAII in languages that 
don't have RAII, so I don't think it's really justifiable to argue that 
Python only gives one obvious way to do it.

D has three: RAII, scope guard, and try-catch-finally. As far as I'm 
concerned, the only reason t-c-f isn't taken out to the woodshed and 
shot is to make it easy to translate code from other languages to D.


>>> Maybe you are right, but the with statement plays very well with the
>>> "explicit is better than implicit" of Python :)
>>>
>>> Again, is flexibility vs complexity.
>> Another principle is abstractions should be in the right place. When
>> the abstraction leaks out into the use of the abstraction, it's user
>> code complexity. This is a case of that, I believe.
> 
> Where is the code complexity here, I can't see it.

The code complexity is suppose I create a mutex object. Every time I get 
the mutex, I want the mutex to be released on all paths. With RAII, I 
build this into the mutex object itself. Without RAII, I have to add in 
the exception handling code EVERY place I use the object. If I change 
the abstraction, I have to go and change every use of it. To me, that's 
code complexity, not flexibility.

A proper abstraction means that if I change the design, I only have to 
change it in one place. Not everywhere its used.


> The thing is, I never used them and never had the need to. Don't ask me
> why, I just have very few errors when coding in Python. So it's not really
> *needed*.

I agree that static analysis isn't needed. The better statement is is 
there a benefit to it that exceeds the cost?