Hello Guilers,
Since I find this exercise interesting, I come up with another demo. The
trick is to think of string as a list of characters (like in Haskell)
and to use the fact that append can be written as an unfold.
Let's begin:
1. Use SRFI-1 and SRFI-26
(use-modules (srfi srfi-1)
Just for kicks, to learn string-unfold, I made an ugly version of string-append:
(define (ugly-string-append . str-l)
;; p: seed |-> #t|#f predicate to indicate stop
(define (p seed) (null? seed))
;; f: seed |-> charoutput function
(define (f seed) (string-ref (cddar seed) (caar se
