Exercise 3.37: The
celsius-fahrenheit-converter procedure is cumbersome when compared with
a more expression-oriented style of definition, such as


(define (celsius-fahrenheit-converter x)
  (c+ (c* (c/ (cv 9) (cv 5))
          x)
      (cv 32)))

(define C (make-connector))
(define F (celsius-fahrenheit-converter C))

Here c+, c*, etc. are the “constraint” versions of the
arithmetic operations.  For example, c+ takes two connectors as
arguments and returns a connector that is related to these by an adder
constraint:


(define (c+ x y)
  (let ((z (make-connector)))
    (adder x y z)
    z))

Define analogous procedures c-, c*, c/, and cv
(constant value) that enable us to define compound constraints as in the
converter example above.161