Reddit: why aren't people using D?

[Ary Borenszweig]

Daniel Keep escribió:
> 
> Walter Bright wrote:
>> Daniel Keep wrote:
>>> That's true, but you haven't addressed the other side of it: property
>>> setters.
>> Right. Consider the case where there's a pure function with no
>> arguments, and an overload with the same name and one argument, and no
>> other overloads. Wouldn't it be reasonable to take that as a property
>> setter?
>>
>>> With D, you would need to explicitly state which methods are properties
>>> manually somehow; dunno how you would, though.  Especially when you
>>> consider subclassing and mixins.
>> See my rule above - I think it'll work.
> 
> Actually, I've now come up with a counter-example for the idea of using
> pure at all:
> 
> class Lazy(T)
> {
>     private
>     {
>         T v;
>         T delegate() dg;
>     }
>     this(T delegate() dg) { this.dg = dg; }
>     T value()
>     {
>         if( dg !is null )
>         {
>             v = dg();
>             dg = null;
>         }
>         return v;
>     }
> }
> 
> You can't make value pure, but it is supposed to be a property.  One of
> the examples Nick gives in DIP4 is a property that accesses an SQL
> database; there's no way to make that pure!

Exactly! That's why I said "kind of pure" (well, maybe I didn't say that 
:-P), but the idea is that properties don't modify anything visible from 
outside of the symbol they are contained in. But it's hard to define 
what that means...