Properties

[Vishaal]

dsimcha Wrote:

> == Quote from BCS (ao at pathlink.com)'s article
> > Reply to Vishaal,
> > > Properties, such as array.length, should return lvalues to allow:
> > > a.length += 8;
> > > or other similar statements.
> > I think there is a (long standing) bug report about that one. Maybe if enough
> > people gripe about it it will get fixed! (NOT said sarcastically!)
> 
> Yeah, this has been mentioned in the past before.  The most obvious way to make it
> work w/o any breaking or significantly bulk-adding changes would be to define
> foo.length += 8 to mean foo = foo.length() + 8, or foo.length++ mean foo =
> foo.length + 1.  This would be pure syntactic sugar, as it is when working with
> primitives.
> 
> One problem that comes to mind is if, instead of length, which is presumably some
> kind of integer, you have a property for some user defined type with operator
> overloading.  This user-defined type could define opAdd to do something
> arbitrarily different from opAddAssign.  Even if we assume that no reasonable
> programmer would do this and treat this as a "who cares?" corner case, there's
> still the problem of opInc and opAddAssign being much cheaper in some cases than
> opAdd.  For example, in some cases opAdd might require copying of a whole bunch of
> stuff, where opInc or opAddAssign just increments a single primitive under the hood.
> 
> Bottom line is, unless we assume that properties of user-defined types aren't
> important, we need a better solution.  Oh yeah, and on the more special case of
> arrays, which the compiler already treats as special, yes, foo.length += 2 should
> be legal.  As far as I can tell, this is a no-brainer.

The two methods aren't mutually exclusive. We could let users write opAddAssign if they want but if there would be no benefit (or if they don't care about memory) they wouldn't have to write an opAddAssign and the compiler would expand it.
++gripes.length;

Sorry, gripes.length = gripes.length + 1;