[Python-ideas] [Wild Idea] Static Ducks

Masklinn masklinn at masklinn.net
Tue Sep 22 22:55:09 CEST 2009

On 22 Sep 2009, at 22:17 , Steven D'Aprano wrote:
> On Wed, 23 Sep 2009 02:35:49 am Masklinn wrote:
>> On 22 Sep 2009, at 17:46 , Steven D'Aprano wrote:
>>> On Wed, 23 Sep 2009 12:25:32 am Masklinn wrote:
>>>> On 22 Sep 2009, at 15:16 , Steven D'Aprano wrote:
>>>>> On Tue, 22 Sep 2009 01:05:41 pm Mathias Panzenböck wrote:
>>>>>> I don't think this is a valid test to determine how a language
>>>>>> is typed. Ok, C++ is more or less weakly typed (for other
>>>>>> reasons), but I think you could write something similar in C#,
>>>>>> too. And C# is strongly typed.
>>>>> Weak and strong typing are a matter of degree -- there's no
>>>>> definitive test for "weak" vs "strong" typing, only degrees of
>>>>> weakness. The classic test is whether you can add strings and
>>>>> ints together, but of course that's only one possible test out of
>>>>> many.
>>>> And it's a pretty bad one to boot: both Java and C# allow adding
>>>> strings and ints (whether it's `3 + "5"` or `"5" + 3`) (in fact
>>>> they allow adding *anything* to a string), but the operation is
>>>> well defined: convert any non-string involved to a string (via
>>>> #toString ()/.ToString()) and concatenate.
>>> I don't see why you say it's a bad test. To me, it's a good test,
>>> and Java and C# pass it.
>> Uh no, by your criterion they fail it: both java and C# do add
>> strings and integers without peeping.
> What are you talking about? Using Python syntax, we might write:
> assert "2"+2 == 4
> This test will FAIL for Python, Pascal and other strongly typed
> languages, and PASS for weakly typed languages. (For some languages,
> like Pascal, you can't even compile the test!)
Ah I see, we used different meanings for "fail" here. I was thinking  
of "failing the test" by accepting to run this piece of code (which I  
find obviously incorrect).

>>> If you're only criterion is that an operation is well-defined,
>>> then "weak typing" becomes meaningless...
>> I don't think I defined any criterion of strong/weak typing.
> You conceded that C# adds strings and ints, but disputed that this  
> fact
> makes C# weakly typed on the basis that (I quote) "the operation is
> well defined".
I didn't dispute C#'s strong or weak typing (again, I consider this  
line of inquiry utterly worthless). I merely noted that the operation  
was clearly defined in the documentation, and am sorry if it came out  
as anything but a "note of interest".

> There's nothing about the definition of weakly typed
> languages
There is not definition of weak typing.

>> As far
>> as I'm concerned, and as I've already mentioned in this thread, the
>> whole weak/strong axis is meaningless and laughable.
> I agree that treating weak/strong as a binary state is an
> over-simplification, but a weak/strong axis is perfectly reasonable.
I really don't think so. Once again, because there is nothing formal  
about the concept, and everybody just make up their own definition of  
the axis as they go.

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