How to code simple data 1a: Beginning Student Language - my problem set solutions

problem_sets.rkt

;;---------------------------
;; arithmetic expression
;;---------------------------
(* 3 5 7)
(* (* 3 5) 7)




;;---------------------------
;; tile-starter
;;---------------------------
(above (beside(square 20 "solid" "blue")
              (square 20 "solid" "yellow"))
       (beside(square 20 "solid" "yellow")
              (square 20 "solid" "blue")))




;;---------------------------
;; compare-images-starter.rkt
;;---------------------------
(define IMAGE1 (rectangle 10 15 "solid" "red"))
(define IMAGE2 (rectangle 15 10 "solid" "red"))


(if (> (image-height IMAGE1)
       (image-height IMAGE2))
    "IMAGE1 is taller than IMAGE2"
    "IMAGE1 is not taller than IMAGE2")

(if (< (image-width IMAGE1)
       (image-width IMAGE2))
    "IMAGE1 is narrower than IMAGE2"
    "IMAGE1 is not narrower than IMAGE2")

(if
 (and (=(image-width IMAGE1)
        (image-width IMAGE2))
      (=(image-height IMAGE1)
        (image-height IMAGE2)))
"IMAGE1 has both the same width AND height as IMAGE2"
"IMAGE1 does not have the same width AND height as IMAGE2")



;;---------------------------
;; more-foo-evaluation
;;---------------------------
(define (foo n)
  (* n n))

;define function called but nothing to evaluate
(foo (+ 3 4))
;function arguments (n) replaced by 7
(foo 7)
(* 7 7)
49





;;---------------------------
;; function-writing-starter
;;---------------------------
(define (returnsTheLargerNumber x y) (if(> x y)x y))

(returnsTheLargerNumber 25 10)




;;---------------------------
;; foo-evaluation
;;---------------------------
(define (foo s)
  (if (string=? (substring s 0 1) "a")
      (string-append s "a")
      s))

(foo (substring "abcde" 0 3))

(foo "abc")

;"abc" replaces every instance of the s arg in the function definition

(if (string=? "a" "a")
    (string-append "abc" "a")
    "abc")

(if #true (string-append "abc" "a") "abc")


(string-append "abc" "a")

"abca"