Start with small tweaks as proof of concept.

bank-account.scm

@@ -66,17 +66,7 @@
    (cons (cons transaction (car account))
 	 (cdr account)))
 
- ;; Creates a new bank transaction. The order of elements is
- ;; well-suited for fast access to commonly used fields.
- (define (make-bank-transaction id date amount currency varsym)
-   (list varsym amount currency date id))
-
- ;; Accessors for the fields actually used
- (define bank-transaction-varsym car)
- (define bank-transaction-amount cadr)
- (define bank-transaction-currency caddr)
- (define bank-transaction-date cadddr)
- (define (bank-transaction-id tr)
-   (list-ref tr 4))
+ ;; Creates a new bank transaction.
+ (define-record bank-transaction id date amount currency varsym)
 
  )