Bienvenido a DrScheme, versión 372 [3m].
Lenguaje: Muy Grande (incluye MrEd y Avanzado).
> (define i-stack% (interface () push! pop! is-empty?))
> (define i-nombrable% (interface () get-nombre set-nombre))
> (define stack% 
  (class* object% (i-stack% i-nombrable%)
      (init-field (name 'stack))
      (field (stack null))

      (define/public (push! v)
        (set! stack (cons v stack)))

      (define/public (pop!)
        (let ((v (car stack))) 
          (set! stack (cdr stack)) 
          v))

      (define/public (is-empty?) 
        (null? stack))

      (define/public (print-name)
        (display name) 
        (newline))

      (super-new)))

. class*: interface-required method missing: set-nombre for class: stack% for interface: i-nombrable%
> (define stack% 
  (class* object% (i-stack% i-nombrable%)
      (init-field (name 'stack))
      (field (stack null))

      (define/public (push! v)
        (set! stack (cons v stack)))

      (define/public (pop!)
        (let ((v (car stack))) 
          (set! stack (cdr stack)) 
          v))

      (define/public (is-empty?) 
        (null? stack))

      (define/public (print-name)
        (display name) 
        (newline))
    
      (define/public (get-nombre)
        name)
    
    
      (define/public (set-nombre nuevo-nombre)
        (set! name nuevo-nombre))

      (super-new)))

> (define s1 (new stack%))
> (define s2 (new stack% (name 'pila)))
> (send s2 get-nombre)
pila
> (send s1 get-nombre)
stack
> (send s1 push! 'hola)
> (send s1 push! 12)
> (send s1 pop!)
12
> (send s1 pop!)
hola
> (send s1 pop!)
. car: expects argument of type <pair>; given ()
> (define fancy-stack% 
  (class stack%
    (inherit-field name)

    (define/override (push! v)
      (super push! (cons 'fancy v)))

    (super-new)))
> (define sf (new fancy-stack%))
> (send sf push! 'hola)
> (send sf push! 13)
> (send sf pop!)
(fancy . 13)
> (send sf pop!)
(fancy . hola)
> (send sf pop!)
. car: expects argument of type <pair>; given ()
> (define double-stack% 
  (class stack%
    (inherit push!)

    (define/public (double-push! v) 
       (push! v) 
       (push! v))

    (super-new (name 'double-stack))))

> (define ds (new double-stack%))
> (send ds double-push! 'hola)
> (send ds get-nombre)
double-stack
> (send ds pop!)
hola
> (send ds pop!)
hola
> (send ds pop!)
. car: expects argument of type <pair>; given ()
> (define safe-stack%
   (class stack%
      (inherit is-empty?)

      (define/override (pop!) 
         (if (is-empty?) 
            #f 
            (super pop!)))

      (super-new)))

> (define s4 (new safe-stack%))
> (send s4 push! 'hola)
> (send s4 pop!)
hola
> (send s4 pop!)
#f
> (define safe-stack%
   (class stack%
      (define/override (pop!) 
         (if (super is-empty?) 
            #f 
            (super pop!)))

      (super-new)))

super: identifier for super call does not have an override, override-final, overment, or inherit/super declaration in: is-empty?
> (define safe-stack%
   (class stack%
      (define/override (pop!) 
         (if (send this is-empty?) 
            #f 
            (super pop!)))

      (super-new)))

> (define s5 (new safe-stack%))
> (send s5 push! 'hola)
> (send s5 pop!)
hola
> (send s5 pop!)
#f
> (define i-extended-stack% (interface (i-stack%) size))

> (define extended-stack%
   (class* object% (i-extended-stack%)
      (inherit-field stack)

      (define/public (size)
         (length stack))

      (super-new)))

. class*: superclass does not provide field: stack for class: extended-stack%
> (define extended-stack%
   (class* object% (i-extended-stack%)
     (stack null)
      (define/public (size)
         (length stack))

      (super-new)))

. class*: interface-required method missing: is-empty? for class: extended-stack% for interface: i-extended-stack%
> (define extended-stack%
   (class* safe-stack% (i-extended-stack%)
      (inherit-field stack)

      (define/public (size)
         (length stack))

      (super-new)))

> (define name-mutator (class-field-mutator stack% name))
(define name-selector (class-field-accessor stack% name))
> name-mutator
#<primitive:set-object:stack%-field1!>
> (name-mutator s1 'pepito)
> (name-selector s1)
pepito
> (send s1 get-nombre)
pepito
> (field-names s1)
(stack name)
> (class s1)
. class*: superclass expression returned a non-class: #(struct:object:stack% ...) for class: ...eshow/tool.ss:350:8>:191:2
> (is-a? s1 stack%)
#t
> (is-a? s1 fancy-stack%)
#f
> (is-a? s3 fancy-stack%)
. reference to undefined identifier: s3
> (define contador%
   (let ((total 0))
      (class object%
         (init-field (c 0))
         (define/public (inc)
            (set! c (+ 1 c))
            (set! total (+ 1 total))
            c)
         (define/public (get-total)
            total)
         (super-new))))
> contador%
#<struct:class:contador%>
> total
. reference to undefined identifier: total
> (define c1 (new contador%))
(define c2 (new contador%))
(define c3 (new contador%))
> (send c1 inc)
(send c1 inc)
(send c1 inc)
(send c2 inc)
(send c2 inc)
(send c3 inc)
1
2
3
1
2
1
> (send c3 total)
. send: no such method: total for class: contador%
> (send c3 get-total)
6
> (send c2 get-total)
6
>