#lang scheme/base

(provide (all-defined-out))

(define (log:
         #:tag [tag #f]
         fmt . args)
  (apply printf
         (string-append (if tag
                            (format "~a: " tag)
                            ";; ")
                        fmt)
         args))

;; Code instantiation
(define (loading str)
  (log: "~a\n" str))