tail const

[Michel Fortin]

On 2010-12-02 16:14:58 -0500, "Steven Schveighoffer" 
<schveiguy at yahoo.com> said:

> On Thu, 02 Dec 2010 07:09:27 -0500, Michel Fortin  
> <michel.fortin at michelf.com> wrote:
>> My only concern with the "const(Object)ref" syntax is that we're 
>> reusing  'ref' to denote an object reference with different properties  
>> (rebindable, nullable) than what 'ref' currently stands for. But it  
>> remains the best syntax I've seen so far.
> 
> Where it would be beneficial is in mimicking the tail-const properties 
> of  arrays in generic ranges.
> 
> I have a container C, which defines a range over its elements R.
> 
> const(R) is not a usable range, because popFront cannot be const.  So 
> now  I need to define constR, which is identical to R, except the 
> front()  function returns a const element.
> 
> So now, I need the same for immutable.
> 
> And now I need to triplicate all my functions which accept the ranges, 
> or  return them.
> 
> And I can't use inout(R) as a return value for ranges.
> 
> If you can solve the general problem, and not just the class 
> tail-const,  it would be hugely beneficial.
> 
> My thought was that a modifier on const itself could be stored in the  
> TypeInfo_Const as a boolean (tail or not), and the equivalent done in 
> dmd  source itself.

I'm not sure I get the problem. Can you show me in code?

-- 
Michel Fortin
michel.fortin at michelf.com
http://michelf.com/