The Status of Const

[Tomek Sowiński]

Jonathan M Davis napisał:

> On Friday, August 13, 2010 14:10:20 Tomek Sowiński wrote:
>> Glad you like it. Time ago I had an overzealous attempt to port QuantLib
>> to D and I quickly found out that the *only* sort of const I needed was
>> tail const. It's what I ended up declaring fields of my structs because
>> if just one field is from-head const, the restrictions are basically the
>> same as if the whole struct was const (which is correct but...). It's
>> what the parameters of pure functions should implicitly be declared to
>> (no big deal, but still). From-head const gives me no upper hand in the
>> multi-threaded domain, just pain in my rectum domain. Sure, from-head
>> const is at times useful, but tail const is the workhorse.
> 
> That's exactly why final in Java is so useless for objects. It makes the
> wrong thing const. How often do you have const pointers in C++? Very
> rarely. How often do you have pointers to const in C++? All the time
> (assuming that you're trying to be at all const-correct anyway). At the
> moment, D is falling into a pit similar to that of Java with const and
> references. D's is better since the object _is_ const, but since you
> usually just want the object const, not the reference, it's incredibly
> counter-productive.

I agree with the content, but not the tone. D's const makes all other mainstream const systems look petty. Applying the concept of 
transitivity has been revolutionary (hail Walter). Tail const is just a cable to the socket to make this wonderful device work out-of-box for 
programming masses.


Tomek