Stepping back and looking at constness from another angle.

[Bruno Medeiros]

David B. Held wrote:
> Regan Heath wrote:
>> [...]
>> - local variables are (until manually/explicitly assigned to another 
>> such)
>> the 1st and only copy/reference of/to the data.
>>
>> - function parameters are implicitly a copy/alias of data.  Once you have
>> aliases you have complication and once you have complication you greatly
>> increase the chances of unexpected changes and therefore bugs.
>> [...]
> 
> Ok, Bruno probably won't like this, but he makes a great point about 
> orthogonality.  The killer argument for orthogonality, IMO, is generics. 
>  Remember that function argument lists are type tuples.  If we say that 
> function arguments are const by default, that means that a given type 
> tuple has different meanings depending on whether it is used in a 
> function argument context or a non-function argument context.  In fact, 
> it could have exactly the *opposite* meaning, which would be the worst 
> kind of non-orthogonality.  This may seem like a faraway problem, 
> because I don't believe you can construct functions by assembling type 
> tuples and pasting them onto bits of code.  But if we cement in this bit 
> of non-orthogonality, we guarantee that such a feature is either awkward 
> or impossible in the future.
> 
> Dave

Just for the record, I'm not an unconditional fan of orthogonality 
(otherwise I'd be using LISP-family languages). There are various 
syntactic sugars, and also "semantic sugars", that breach orthogonality 
but are useful and practical enough to justify them. What I am 
unconditionally against are orthogonality breaches that serve little or 
no useful purpose, like some of the examples mentioned in the other 
thread (like static arrays).
As for this issue, I guess we all agree that there are two beneficial, 
but apparently mutually exclusive aspects:
* The added safety of const-by-default (or syntactic sugar, depending on 
how you see it).
* The kept orthogonality of declaring function parameters with tuples.
Which aspect do I prefer? I'm not sure yet. Frankly, I'm hoping we could 
come up with a solution that didn't require sacrificing one over the 
other (or at least minimized that).

-- 
Bruno Medeiros - MSc in CS/E student
http://www.prowiki.org/wiki4d/wiki.cgi?BrunoMedeiros#D