From: Josh Cheek <josh.cheek@...>
Date: 2011-01-18T10:32:19+09:00
Subject: Re: Why Ruby Does Not Support Method Overloading?

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On Mon, Jan 17, 2011 at 7:09 PM, Su Zhang <zhangsu@live.com> wrote:

> Common-Lisp does support multiple dispatch, but it does so by
> including a type modifier to the arguments so that they can be checked
> against the actual runtime type of arguments, which, IMO, is as
> unpleasant as doing something like the following in a single method
> definition:
>
> case arg
> when String
>    # ...
> when Symbol
>    # ...
> end
>
>
I went through a Lisp book over the winter break, and I took it a different
way: that it was essentially a way to define a receiver for a function. (not
sure if that is good terminology)

In other words, I took it like:
class Array
  def size
    Array size finding code
  end
end

class Hash
  def size
    Hash size finding code
  end
end

Now, hash.size invokes a different method than array.size. So in Lisp this
would maybe look like

(defmethod size ((self array))
  array size finding code )

(defmethod size ((self hash-table))
  hash-table size finding code )

And unlike all the other functions in Lisp, which share the same namespace,
size knows which function to invoke (size ary) invokes a different function
than (size hash). So I think that defmethod is an appropriate name, because
that is how I consider them, modular like methods, as opposed to created in
one canonical place like a case statement.

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