use define-record-writer to set custom writer to <array> type

piclib/picrin/array.scm

@@ -89,7 +89,7 @@
   (define (array-for-each proc ary)
     (for-each proc (array->list ary)))
 
-  (define (print-array array)
+  (define-record-writer (<array> array)
     (call-with-port (open-output-string)
      (lambda (port)
        (display "#.(array" port)
@@ -101,8 +101,6 @@
        (display ")" port)
        (get-output-string port))))
 
-  (record-set! <array> 'writer print-array)
-
   (export make-array
           array
           array?