On Tue, 13 Dec 2011 07:25:10 -0500, Somedude <[email protected]> wrote:
Le 13/12/2011 01:25, Mehrdad a écrit :
In every language I've seen that has "properties" (C#, Python), they are:
- _Defined_ like methods
- _Used_ like variables
The trouble is, this isn't true with D.
Consider:
struct Struct
{
int delegate() randgen1 = ...;
@property
int delegate() randgen2() { ... }
}
Struct s;
auto result = s.randgen2(); // This doesn't do the user expects
It is *not* possible, in D, to transparently use either one -- you have
to treat properties, like methods, not like variables. Except that this
is inconsistent -- in most other cases, you don't need to do that.
Or for example:
Struct s;
auto a = &s.randgen1;
auto b = &s.randgen2; // Should be an error
IMO, properties should not be callable with parentheses at all.
Something like C# -- they should generate getter and setter methods
instead, or the like.
Furthermore, taking the address of a property should only work if you
can take the address of its _value_. If you need the address of the
actual function, then I think a corresponding getter method might be
easier to use.
It gets even /worse/ in templated code, because you have no idea whether
an alias is referring to a property or to a variable or whatever.
Making this change would obviously break code, but the break is
obviously _trivial_ to fix: just remove extra parentheses. It won't
exactly be the kind of breakage that causes headaches.
So should this be fixed?
My question is: what is the use case for properties in D ?
The original use case for properties (in general) was to allow source level
compatibility when one re-factored a public field from a variable to a method.
Since then, properties have become a common tool to hide fields from the public
interface (to allow for overloading, etc) but retain field like syntax. In D,
the technical use case for @property was to resolve an ambiguity when
re-factoring a zero argument delegate field to a method. Also, there was a
cognitive dissonance between D's properties and those of C# and python.
