Re: Closures versus objects

On 2/16/07, Spencer Schumann <[email protected]> wrote:
>  The method dispatch mechanisms provided by
> objects take namespace control one step further, which is often very
> useful; in Ruby:
>
>  s = "abcd"
>  s.length
>  a = [1, 2, 3]
>  a.length
>
> seems much more elegant to me than Scheme's
>
>  (let ((s "abcd")
>        (ls '(1 2 3)))
>    (string-length s)
>    (length ls))

You're picking on the non-polymorphic primitives.  Suppose there were a
generic function `len' that returned the length of a string, vector,
list, or whatever
it made sense for.  Then you have this:

(len "abc") => 3
(len '(1 2 3)) => 3

etc.

No difference from Ruby except for the syntax.

But Ruby syntax has a major disadvantage!  Suppose you wanted to late-bind the
method name?  In Scheme you'd do this:

(let ((method   (select-method  len first last)))
  (method "abcd"))

but you can't bind the name of a method identifier in Ruby:

  method = select-method (len, first, last)
  s = "abcd"
  s.method

won't work.




-- 
~jrm