Programmation déclarative - Q1 - 08/2011

(define (add-multiplicity l e)
  (if (null? l)
      (list (cons e 1))
      (if (equal? (car (car l)) e)
          (cons (cons e (+ (cdr (car l)) 1)) (cdr l))
          (cons (car l) (add-multiplicity (cdr l) e))
          )
      )
  )

(define (multiplicitylst lst)
  (letrec
      ((walk (lambda (list mul)
               (if (null? list)
                   mul
                   (walk (cdr list) (add-multiplicity mul (car list)))
                   )
               )
             ))
    (walk lst '())
    )
  )