On Thu, 07 Feb 2013 15:02:41 -0000, Steven Schveighoffer
<schvei...@yahoo.com> wrote:
On Wed, 06 Feb 2013 23:26:03 -0500, Chad Joan <chadj...@gmail.com> wrote:
On 02/05/2013 09:45 PM, Steven Schveighoffer wrote:
...
The semantic rewrite stuff is something I don't feel strongly either
way. It would be nice, but at the same time, it doesn't feel necessary
to me. One can always simply avoid it by not using the operators on
properties.
A core feature of properties is that variables can be migrated to them
(and back) without breaking any of the caller's code. Forbidding more
than half of D's operators on them will definitely break this attribute.
I find this explanation lacking. A field supports operations that are
impossible to implement with properties, there will never be a
non-code-breaking change from a field to a property. So it's a matter
of "how much" breakage you want to allow. This is really a judgment
call, there is no "right" answer. The closest you can get to a field is
to ref an actual field. But in that case, I don't see the point of the
property, since you give unfettered access to the field!
The whole point of having properties that I see is to implement things
you CAN'T implement with a field, or are more cumbersome. Like
read-only fields. Such a change would necessarily and on purpose break
code.
There are several "points" to properties it would seem:
http://en.wikipedia.org/wiki/Property_(programming)
I have heard the goal Chad mentions said numerous times in similar
discussions (to allow migration of fields to properties and back without
breaking caller code) and I imagine this would be true and work in all
cases for languages which don't have pointers, perhaps.
But as D has pointers there can and probably does exist caller code which
takes the address of a public field and would therefore simply break if
that field was changed into a "property" (AKA method call).
Now, perhaps there is some magic the compiler could do to make it work
again, but if to achieve this we really have to jump through some crazy
hoops or add complexity and edge-cases to the language then it's just not
worth it, IMO.
And, as Steven has said implementing read-only fields and adding layers of
functionality are 2 other goals/points of properties and these are
certainly useful by themselves, with or without any other benefits.
R
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