(picrin protocol) の使用例。 ライブラリシステムとの相性？

lib1.sld

(define-library (lib1)
  (import
   (scheme base)
   (picrin protocol))

  (begin
    (define-protocol (SHOW t)
      (show t))
    )
  (export show SHOW))
  

lib2.sld

(define-library (lib2)
  (import
   (picrin class)
   (picrin protocol)
   (lib1)
   (scheme base))

  (begin
    (define-instance (SHOW <boolean>)
      (lambda (x)
        (if x
            "#<boolean true>"
            "#<boolean false>")))
    
    (define (show-number-1)
      (show 1))

    (define (show-true)
      (show #true))
    )

  (export show-number-1 show-true))

test.scm

(import (lib1)
        (lib2)
        (scheme base)
        (scheme write)
        (picrin class)
        (picrin protocol))

(define-instance (SHOW <number>)
  (lambda(x)
    (string-append "#<number " (number->string x) ">")))

(display (show-number-1))
(newline)
(display (show-true))
(newline)