I'm back in .NET land
after living, pretty much exclusively, for the last two years in Java-and-Ruby land and while I generally
like C#, I ran across
something today that is really stupid. It involves operator
overloading. While I actually like operator overloading and think it
can be a powerful thing, the implementation of one facet of it in C# is just
wrong. The problem is that they force you to override certain
operators in pairs instead of defining them in terms of each other or
in terms of a single method.
In other words, if I define == to check equality
then I also have to define != to check
inequality! Why in the world should I have to do that since
inequality is the opposite of equality and can be defined in terms of
the equality operator? The same holds true for < &
> and <= & >=. What you end up
with is something like this:
where the != operator just negates a call to
==. You would repeat this process for the other two pairs if
you wanted to provide them. (And yes, I know if you provide your own
== then you have to also provide a GetHashCode method.) There
is no reason that the developer should have to do anything more than
provide a comparison operator and then let the system define
the other methods in terms of that comparison...
And that's exactly what Ruby
does. If you include the module called "Comparable" in your class, and
provide a comparison method called <=> (called the
"spaceship method" because that's what it looks like) then you get
==, !=, <, <=, > and >= for free! That's right,
by defining one method you get six defined in terms
of it automatically. Now that's how it should be
done! Which results in code like this:
1 class Foo
2 include Comparable # Here's where the majic starts
3
4 attr_accessor :val
5
6 def initialize(val)
7 self.val = val
8 end
9
10 # comparison method; all others defined in terms of this
11 def <=>(other)
12 val <=> other.val
13 end
14 end
Obviously these are both trivial classes but I think you get the
point. There is no reason why you should have to define more than one
method to get all the normal comparisons that you would expect in a
language.
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