(require "lists.BRU")
; suboptimal:
[(define (%insert-inserter may-precede? new-element ls)
        (cond
                ((null? ls) (list new-element))
                ((may-precede? new-element (first ls)) (cons new-element ls))
                (else (cons (first ls) (%insert-inserter may-precede? new-element (rest ls))))))

 (define (insertion-sort may-precede? ls)
      ((fold-list '() (%insert-inserter may-precede?)) ls))]