Suggestion: object const'ness

[Hasan Aljudy]

Regan Heath wrote:
> On Sat, 20 May 2006 20:44:52 -0400, Jarrett Billingsley  
> <kb3ctd2 at yahoo.com> wrote:
> 
>> "Tom" <ihate at spam.com> wrote in message
>> news:e4ll86$q0e$1 at digitaldaemon.com...
>>
>>> One of the flaws of the language IMHO. Also in/out/inout is flawed and
>>> seems merely informative instead of being strict in allowing/disallowing
>>> parameter modification. I'm on the side of const-like solution and  
>>> *TRUE*
>>> in/out/inout param attributes. When I first read about D and all these
>>> promising features I was really amazed till I try some of them (like
>>> in/out/etc). I felt disappointed though I still love the language 
>>> and  it's
>>> a shame this little stuff doesn't work as one expect.
>>
>>
>> Just curious; what do you mean by "true" in/out/inout?  Do you mean that
>> "in" parameters should not be modifiable (kind of like const)?
> 
> 
> I believe that's exactly what he means. I proposed the same thing in 
> one  of the many past const debates. It just makes sense to me that if 
> a  parameter is passed as 'in' you will not be modifying it, if you 
> were  modifying it you'd clearly be passing it as 'inout'.
> 
> 'in' is the default parameter type, so this would mean that by default  
> parameters are not modifyable. Which in turn means you have to actually  
> think about and indicate the parameters you are going to modify.
> 
> There remains a problem that passing say an object reference by 'in' 
> only  really says "I will not modify this object reference", and gives 
> no  guarantee about the data to which it refers (same goes for array  
> references, or any kind of reference). So there is actually several 
> layers  of immutability to handle, somehow.
> 
> I'm very much in favour of some sort of "const" solution which involves  
> 'in', 'out', etc.
> 
>> If so, what about out/inout?
> 
> 
> 'out'   - initialized to type.init and expects to be modified (not const)
> 'inout' - expects to be modified (not const)
> 
> Regan

huh? if you pass an object reference as in you shouldn't be able to 
manipulate the object?!!
In what sense is that a "true" in?

That's just an arbitrary restriction.