(define (lay:string:downcase s)
  (let* ((l (string-length s))
         (r (make-string l)))
    (let loop ((i 0))
      (if (eq? i l)
        r
        (begin
          (string-set! r i (char-downcase (string-ref s i)))
          (loop (add1 i)))))))

(define (lay:string:trim s)
  (define (trim-head lst)
    (let loop ((lst lst))
      (if (and (pair? lst) (char=? #\space (car lst)))
        (loop (cdr lst))
        lst)))
  (list->string (reverse (trim-head (reverse (trim-head (string->list s)))))))