(unit/sig framework:version^
  (import [mzlib:string : mzlib:string^]
	  [mzlib:function : mzlib:function^])

  (rename [-version version])

  (define specs null)

  (define -version
    (lambda ()
      (mzlib:function:foldr
       (lambda (entry sofar)
	 (match entry
	   [(sep num) (string-append sofar sep num)]))
       (version)
       specs)))

  (define add-spec
    (lambda (sep num)
      (set! specs (cons (list (mzlib:string:expr->string sep)
			      (mzlib:string:expr->string num))
			specs))))
  
  '(add-version-spec ': 5))