pyramid.clj

;; The goal of this program is to draw a pyramid in the terminal with a given height.
;;
;; Examples:
;;
;; ↓ height = 1
;;
;; ∆
;;
;; ↓ height = 2
;;
;;  ∆
;; ∆∆∆
;;
;; ↓ height = 3
;;
;; ..∆..
;; .∆∆∆.
;; ∆∆∆∆∆
;;
;; ↓ height = 6
;;
;;      ∆
;;     ∆∆∆
;;    ∆∆∆∆∆
;;   ∆∆∆∆∆∆∆
;;  ∆∆∆∆∆∆∆∆∆
;; ∆∆∆∆∆∆∆∆∆∆∆
;;

(ns pyramid
  (:require [clojure.string :refer [join]]
            [clojure.test :refer [deftest is]]))

(defn- layer [height story]
  (let [width (- (* 2 height) 1)
        bricks (join (repeat width "∆"))
        padding (join (repeat story "_"))]
    (join [padding bricks padding])))

(defn draw
  "Draws pyramid bottom up"
  ([height] (draw height 0))
  ([height story]
   (case height
     0 ""
     1 (layer height story) ;; reached the top of the pyramid (last iteration)
     (join "\n" [(draw (dec height) (inc story))
                 (layer height story)]))))

(println (draw 0))
(println (draw 1))
(println (draw 2))
(println (draw 3))
(println (draw 6))
(println (draw 10))

(deftest test-layer
  (is (= (layer 1 2) "__∆__"))
  (is (= (layer 2 1) "_∆∆∆_"))
  (is (= (layer 3 0) "∆∆∆∆∆")))

(deftest test-draw
  (is (= (draw 3) "__∆__\n_∆∆∆_\n∆∆∆∆∆")))

;; ---

(defn ward
  "Draws pyramid top down"
  ([height] (ward height (dec height)))
  ([height story]
   (case story
     -1 ""
      0 (layer height story) ;; reached the bottom of the pyramid (last iteration)
      (join "\n" [(layer (- height story) story)
                  (ward height (dec story))]))))

(println (ward 0))
(println (ward 1))
(println (ward 2))
(println (ward 3))
(println (ward 6))
(println (ward 10))

(deftest test-ward
  (is (= (ward 3) "__∆__\n_∆∆∆_\n∆∆∆∆∆")))