shape-geometry.sema

;; shape-geometry.sema — Geometric shapes using match and map destructuring
;; Demonstrates: match on map patterns, {:keys} destructuring, guards

(define (area shape)
  (match shape
    ({:type :circle :radius r} (* pi r r))
    ({:type :rect :w w :h h} (* w h))
    ({:type :triangle :base b :height h} (/ (* b h) 2))
    ({:type :square :side s} (* s s))
    (_ (error f"Unknown shape: ${shape}"))))

(define (perimeter shape)
  (match shape
    ({:type :circle :radius r} (* 2 pi r))
    ({:type :rect :w w :h h} (* 2 (+ w h)))
    ({:type :triangle :a a :b b :c c} (+ a b c))
    ({:type :square :side s} (* 4 s))
    (_ nil)))

(define (describe shape)
  (let (({:keys [type]} shape))
    (let ((a (/ (round (* (area shape) 100)) 100.0))
          (p (perimeter shape)))
      (println f"  ${type}: area=${a}, perimeter=${(if p (round p) "N/A")}"))))

(define shapes
  (list {:type :circle :radius 5}
    {:type :rect :w 4 :h 7}
    {:type :triangle :base 6 :height 3 :a 5 :b 6 :c 7}
    {:type :square :side 3}))

(println "=== Shape Geometry ===\n")
(for-each
  describe
  shapes)

;; Scale a shape
(define (scale shape factor)
  (match shape
    ({:type :circle :radius r} {:type :circle :radius (* r factor)})
    ({:type :rect :w w :h h} {:type :rect :w (* w factor) :h (* h factor)})
    ({:type :square :side s} {:type :square :side (* s factor)})
    (other other)))

(println "\nScaled ×2:")
(->> shapes
  (filter #(not (= (get % :type) :triangle)))
  (map #(scale % 2))
  (for-each describe))

;; Classify by area
(define (classify shape)
  (let ((a (area shape)))
    (match a
      (a when (> a 50) "large")
      (a when (> a 20) "medium")
      (_ "small"))))

(println "\nClassification:")
(for-each
  (fn (s)
    (let (({:keys [type]} s))
      (println f"  ${type} → ${(classify s)}")))
  shapes)