Redefining Scheme Procedures

• There is a built-in Scheme procedure called quotient that does just what our quot does.

• Scheme programmers are free to redefine built-in Scheme procedures:

    (define quotient
      (lambda (n d)
        (cond
          ((< d 0) (- (quotient n (- d))))
          ((< n 0) (- (quotient (- n) d)))
          ((< n d) 0)
          (else    (+ 1 (quotient (- n d) d))))))
  
    (define +
      (lambda (x y)
        (- x y)))
  

• The last example is a bad idea