Last modified on 27 July 2009, at 20:16

The Science of Programming/SwayPresentations/Objects/EnvironmentsAsObjects

Environments as Objects

If you are going to use an existing 'object' as an 'Object', then environments are a better choice.

In Scheme, environments are first-class 'objects'.

  (define (account amount)
      (define (deposit d) (set! amount (+ amount d)))
      (define (withdraw w) (set! amount (- amount w)))
      (procedure-environment (lambda () 1))
      )

We need the 'dot' operator:

   (define (dot obj message)
       (eval message obj)
       )

Now, our account looks like:

   (define a (account 100))
   ((dot a 'withdraw) 10)
   ((dot a 'deposit) 20)

Next Previous Top