(module foo ()
        (import chicken scheme)
        (use lolevel)

        (define-syntax
          let-slots
          (ir-macro-transformer
           (lambda (e i c)
             (let* ((slots (caadr e))
                    (struct-name (cadadr e))
                    (struct (car (cddadr e)))
                    (body (cddr e)))
               `(let ,(map (lambda (s)
                             `(,(i s) (,(symbol-append (i struct-name) '- (i s)) ,struct)))
                           slots)
                  ,@(i body))))))

        (define-record state prompt in out offset line pos return cols max-row)


        (define (prompt-loop ps)
          (let-slots ((pos line in out return) state ps)
                     ps)))