A little Py Vs C++

[Andrei Alexandrescu]

On 11/1/12 6:51 PM, Walter Bright wrote:
> On 11/1/2012 2:20 PM, bearophile wrote:
>> Some complexity comes from the
>> desire to do more and more. As example see this recent request from Manu,
>
> What about all your feature requests? I think you've made more than
> anyone, by a factor of 10 at least!
>
> :-)
>
> As for Manu's request
>
> http://d.puremagic.com/issues/show_bug.cgi?id=8108
>
> I've gone over with him why he needs it, and there's no other reasonable
> way. He needs it for real code in a real application.

I'd argue this actually is part of a category of features that does not 
increase the complexity of the language (quite the contrary in fact). 
This is because stating that declaration+definition in the same file 
won't work takes actually more cognitive load than just allowing it.

By the consistency principle, one should infer unknown parts of a 
complex system from knowing the others. Consider then this setup:

* Declarations (without definition) of functions are allowed.

* Definitions are allowed.

* Declarations and definitions are allowed in distinct files in the same 
project as long as they match.

At this point, it is more tenuous to argue that "same file" is a special 
case that should prevent declarations and definitions to coexist, than 
to just let it happen and let the consistency principle take care of 
explaining it.


Andrei