Extended Type Design.

[Bill Baxter]

Dan wrote:
> Wow...
> 
> I've never put this much thought into const/final stuff.  Ultimately, the program *cannot* prevent data in memory from being changed.  It can at best prevent you from accidentally changing it; hence final and const declarations mean "I don't want anyone to change these, can you raise an error if someone tries to within D?"
> 
> Also, the problem breaks down to 'what am I declaring const?'.  If I declare:
> 
> const int* x; // is it the pointer, or the int?
> 
> This doesn't seem important until you get to:
> 
> const int[int**][]* x; // now what is it?
> 
> Ultimately, you have this problem going through each and every pointer, array and value.  You could theoretically write this:
> 
> const int[int**][]*[char[]][3][17][3,17]* x;  and now what are you going to do?  declare it:
> 
> final const final final const const final final final final final const?
> Even final const! super const! final! const! doesn't work, in fact I agree it makes it worse.
> 
> Good luck getting readability with that.

This:
   const int[int**][]*[char[]][3][17][3,17]* x;

is *already* unreadable (plus I don't think that [3,17] part is legal 
D).  If any reasonable programmer really did have a need for such a type 
then they would probably break it up into aliases with some sort of meaning.

--bb