On Fri, 2012-12-28 at 16:38 +0100, deadalnix wrote:
[…]
> Sure. To make that clear I have to reintroduce the context : I was answering to a post that stated that even if the language don't support immutability, you can have immutability simply by not mutate data.
> 
> To benefit from immutability, you have to be 100% sure that no piece of code will mutate the data ever. If you have no support for that, you break abstraction, because you have to know the internal of every piece of code you use, in order to know if the data are modified or not. If you have to know the internal of each piece of code you use, then abstraction is broken.

I am not sure I would relate this issue to abstraction per se, though it is about preconditions, postconditions and assumptions that can, or cannot, be made.  I think we agree on the substance just differ on the language used to describe the concepts.

> If abstraction is broken, then the ability to code will be reduced as the codebase grow, to a point where nothing is maintainable anymore. When I say that it will not not scale, I'm talking about scaling the technique to a bigger codebase, not actually scaling the resulting program to bigger workload.

OK, I think we agree on substance just differ on the choice of language used to describe this situation. Here though "abstraction" and "broken abstraction" can work for me :-)

This issue is one of the problems with very large Python codebases. They can be got round with functional tests, but strong discipline is needed. Ada and Modula-2 introduced a lot of good stuff!

Thanks for taking the time to go into more depth.

> The subject is quite big, and I have proposed a talk about it in DConf 2013 (I'm waiting for Walter to accept or reject).

Sadly I won't be able to get to the conference: to travel on an aeroplane for longer than about 2 hours I have to lie flat for long periods. This generally means great cost, that is only affordable when someone else is paying, which usually means client-paid consultancy/training gigs.

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