Objects are poor man's closures

Discuss.

The venerable master Qc Na was walking with his student, Anton.  Hoping to prompt the master into a discussion, Anton said "Master, I have heard that objects are a very good thing - is this true?"  Qc Na looked pityingly at his student and replied, "Foolish pupil - objects are merely a poor man's closures."

Chastised, Anton took his leave from his master and returned to his cell, intent on studying closures.  He carefully read the entire "Lambda: The Ultimate..." series of papers and its cousins, and implemented a small Scheme interpreter with a closure-based object system.  He learned much, and looked forward to informing his master of his progress.

On his next walk with Qc Na, Anton attempted to impress his master by saying "Master, I have diligently studied the matter, and now understand that objects are truly a poor man's closures."  Qc Na responded by hitting Anton with his stick, saying "When will you learn? Closures are a poor man's object."  At that moment, Anton became enlightened.

>>2
So, neither are better?

logik++

You can easily do what you do with objects with closures, yet it's not always easy to do what you do with closures with objects.

>>4

Example?

generally private members in objects act like a closure.

let make an object with a struct and a closure (SML):

let new_x a =
  let a = ref a in
  {
     a_acc = fun () -> !a ;
     a_set = fun x  -> a:= x ;
     do = fun () -> succ a ;
  }

wow it looks like an object

lets do a closure using OO

class X {
   var a;
   var a_acc() { return a; }
   a_set(x) { a = x; }
   do() { a++ }
}

I think objects are just fine for what they do. Associating methods and data, exactly what closures do except we often get nice things like inheritance or easy syntax. (Also Ocaml does OO but I didn't feel like it)

LISP

Lain.

12 Name: Anonymous 2011-02-03 6:12