#lang racket

; Often it makes sense to only evaluate a term once and
; then use that value where needed

(+ (* 3 4) (- (* 3 4) (/ 1 (* 3 4))))

; replace each (* 3 4) by variable p which is pre-computed
(define p (* 3 4))
(+ p (- p (/ 1 p)))

; wrap the expression in a closure that captures the p
; and apply it to the result of computing the term
( (lambda (p) (+ p (- p (/ 1 p))) )
  (* 3 4)
  )

; you can do this as much as you want
( (lambda (t1 t2 t3)
    (if (< t1 t2) (* t1 t3) (* t2 t3))
    )
  
  (+ 1 3) 
  (- 4 6)
  7
  )


; in unrestricted Scheme, use the let construction, which places
; the computation of the value beside the variable it is assigned to
(let ( (p (* 3 4)) )
  (+ p (- p (/ 1 p)))
  )

(let (
      (t1 (+ 1 3))
      (t2 (- 4 6))
      (t3 7)
      )
  (if (< t1 t2) (* t1 t3) (* t2 t3))
  )