gistfile1.scm

(define minimize-interval-list
  (lambda (ls)
    (if (null? ls) 
        '() 
        (if (equal? (length ls) 1)
            ls  
            (if (interval-intersects? (car ls) (cadr ls))
                (minimize-interval-list (append (interval-union (car ls) (cadr ls)) (cddr ls)))
                (cons (car ls) (minimize-interval-list (cdr ls))))))))

(define interval-union
  (lambda (i1 i2) 
    (cond ((interval-intersects? i1 i2) (list (list (min (car i1) (car i2)) (max (car (cdr i1)) (car (cdr i2))))))
          (else (list i1 i2)))))

(define interval-contains?
  (lambda (interval number)
    (cond ((< number (car interval)) #f) 
          ((> number (car (cdr interval))) #f) 
          (else #t))))

(define interval-intersects?
  (lambda (i1 i2) 
    (cond ((interval-contains? i1 (car i2)) #t) 
          ((interval-contains? i1 (car (cdr i2))) #t) 
          ((interval-contains? i2 (car i1)) #t) 
          ((interval-contains? i2 (car (cdr i1))) #t) 
          (else #f))))