functional

[grauzone]

Andrei Alexandrescu wrote:
> On 03/10/2010 05:01 PM, grauzone wrote:
>> Andrei Alexandrescu wrote:
>>> There's one final nail in the coffin. In wake of concurrency, de jure
>>> immutability becomes a necessity, not a useful and desirable de facto
>>> convention. Adopting the window dressing but not the essence of FP by
>>> a concurrent language evokes to me a scene in the Marx Brothers: an
>>> otherwise impeccably-dressed gentleman who forgot to put his pants on.
>>
>> Language support is not strictly necessary to get the same effects as
>> immutable types, as far as multithreading is concerned: small data can
>> be copied, and large data can be made read-only by OS syscalls. This
>> just had to be in the message passing library. (As a bonus, it isn't
>> possible to subvert these mechanisms just by casting.)
> 
> That'll never work. The OS granularity is 4KB increments.

Data this small you would simply copy. Because it's so small, copying 
won't have negative performance impact. The OS approach can be used for 
large data (at least in the order of hundreds of KB) and immutable parts 
of the data segment.

> Andrei