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Documentation and tidy up.

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This commit is contained in:
Simon Brooke 2025-08-30 16:13:44 +01:00
parent a4c64297f0
commit 1b5aeeb52e
3 changed files with 199 additions and 60 deletions
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83
index.html
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@ -18,16 +18,19 @@
<script type="application/x-scittle">
(def turtle (atom {:theta 0 :x 0 :y 0 :pen :up :ink "blue"}))
(defn log-turtle! []
(defn log-turtle!
[]
(.log js/console
(apply str
(map #(str % " " (@turtle %) "; ") (keys @turtle)))))
(cons "Turtle: "
(map #(str % " " (@turtle %) "; ") (keys @turtle))))))
(log-turtle!)
(def playing-field (.getElementById js/document "playing-field"))
(defn- not-a-number! [n]
(defn- not-a-number!
[n]
(throw (js/Error. (str "not a number: " n))))
(defn number-or-error!
@ -46,7 +49,6 @@
v (cond (.isNaN js/Number a) 0
(< a 0.5) 0
(<= a 360) a
;; TODO: `rem` is possibly wrong when we get into negative numbers
:else (loop [r a]
(if (<= r 360) r
(recur (- r 360)))))
@ -58,7 +60,6 @@
"Turn the turtle clockwise by this `angle`, expressed in degrees with
respect to the X axis. If `angle` is not a number, throw an exception."
[angle]
(.info js/console (str "(turn! " angle ")"))
(if (number? angle)
(swap! turtle assoc :theta
(sanitise-angle
@ -70,9 +71,12 @@
(defn turn-to!
"Turn the turtle to face `angle`, expressed in degrees with respect to the
X axis. If `angle` is not a number, throw an exception."
X axis. If `angle` is not a number, throw an exception.
**TODO: Note that 180&deg; is currently straight up; this is not intended, it
is intended that 0&deg; should be straight up, and this change will be made
before version 1.0."
[angle]
(.info js/console (str "(turn-to! " angle ")"))
(if (number? angle)
(swap! turtle assoc :theta (sanitise-angle angle))
(not-a-number! angle))
@ -80,13 +84,13 @@
") :: :theta now " (:theta @turtle))))
(defn pen-down!
"Put the turtle's pen down."
"Put the turtle's pen down (i.e., cause line segments to be created)."
[]
(.info js/console "pen-down!")
(swap! turtle assoc :pen :down))
(defn pen-up!
"Lift the turtle's pen up"
"Lift the turtle's pen up (line segments will not be created)."
[]
(.info js/console "pen-up!")
(swap! turtle assoc :pen :up))
@ -104,7 +108,11 @@
(not (pen-down?)))
(defn move-to!
"Move the turtle absolutely to the coordinates `x`, `y`."
"Move the turtle absolutely to the coordinates `x`, `y`. If the
pen is down, create a line element.
**NOTE THAT** this is the only function which creates new graphical
elements."
[x y]
(.info js/console (str "(move-to! " x " " y ")"))
(when (map number-or-error! [x y])
@ -112,14 +120,14 @@
y' (:y @turtle)]
(when (pen-down?)
(let [elt (.createElementNS js/document "http://www.w3.org/2000/svg" "line")
id (gensym "line")]
(.setAttribute elt "id" id)
(.setAttribute elt "x1" x')
(.setAttribute elt "y1" y')
(.setAttribute elt "x2" x)
(.setAttribute elt "y2" y)
(.setAttribute elt "stroke" (or (:ink @turtle) "blue"))
(.appendChild playing-field elt)))
id (gensym "line")]
(.setAttribute elt "id" id)
(.setAttribute elt "x1" x')
(.setAttribute elt "y1" y')
(.setAttribute elt "x2" x)
(.setAttribute elt "y2" y)
(.setAttribute elt "stroke" (or (:ink @turtle) "blue"))
(.appendChild playing-field elt)))
(swap! turtle assoc :x x :y y))))
(def ^:const pi 3.141592653589793)
@ -143,16 +151,12 @@
(defn sin
"Return the sine of this `angle`, considered to be expressed in degrees."
[angle]
(let [v (.sin js/Math (degrees->radians angle))]
(.log js/console (str "(sin " angle ") => " v))
v))
(.sin js/Math (degrees->radians angle)))
(defn cos
"Return the cosine of this `angle`, considered to be expressed in degrees."
[angle]
(let [v (.cos js/Math (degrees->radians angle))]
(.log js/console (str "(cos " angle ") => " v))
v))
(.cos js/Math (degrees->radians angle)))
(defn move!
"Move the turtle forward on its current heading by `distance` units."
@ -170,6 +174,22 @@
(swap! turtle assoc :ink colour)))
(defn draw-tree!
"Draw a tree. This is a fairly crude tree-drawing algorithm;
there's lots of ways it can be improved, consider it a place
to start. Parameters (all numeric) as follows:
`length`: the length of the current segment of the tree;
`left-branch`: the amount to turn left, with respect to the
parent segment, to draw a left branch, in degrees;
`right-branch`: the amount to turn right, with respect to the
parent segment, to draw a right branch, in degrees;
`curvature`: the amount to turn to draw the next segment of
the current stem, in degrees;
`branch-fraction`: the length of a branch segment, as a
proportion of the length of its parent segment;
`trunk-fraction`: the length of the next segment of a stem,
as a proportion of the length of its parent segment;
`depth`: the maximum depth of recursion to allow."
[length left-branch right-branch curvature branch-fraction trunk-fraction depth]
(log-turtle!)
(when (> depth 0)
@ -200,11 +220,13 @@
branch-fraction
trunk-fraction
(dec depth))
(turn! (- 0 right-branch curvature))
(turn! (- 0 right-branch))
(pen-up!)
(move! (- 0 length))))
(defn draw-polygon!
"Draw a regular polygon, with this number of `sides`, each of
this `side-length`."
[sides side-length]
(when {<= 3 sides 360}
(let [angle (/ 360 sides)]
@ -219,11 +241,16 @@
(log-turtle!)
(pen-up!)
(log-turtle!)
(move-to! 350 350)
(move-to! 350 700)
(log-turtle!)
(turn-to! 180)
;; (draw-tree! 100 70 60 5 0.25 0.7 3)
(doall (map #(draw-polygon! % 100) (range 3 20)))
(draw-tree! 100 20 16 8 0.2 0.8 8)
(set-ink! "blue")
(doall (map #(let [v (* 16 (mod % 16))
c (str "rgb(" v "," v "," (- 256 v)")")]
(set-ink! c)
(draw-polygon! % 100))
(range 3 16)))
</script>
</body>
</html>