show and hide turtle

prelude.ld

@@ -1252,6 +1252,16 @@ fn setheading! {
 	(heading as :number) -> add_command! ((:setheading, heading))
 }
 
+fn showturtle! {
+	"If the turtle is hidden, shows the turtle. If the turtle is already visible, does nothing."
+	() -> add_command! ((:show))
+}
+
+fn hideturtle! {
+	"If the turtle is visible, hides it. If the turtle is already hidden, does nothing."
+	() -> add_command! ((:hide))
+}
+
 fn heading/vector {
 	"Takes a turtle heading, and returns a unit vector of that heading."
 	(heading) -> {
@@ -1288,6 +1298,8 @@ fn apply_command {
 		(:penwidth, pixels) -> assoc (state, :penwidth, pixels)
 		(:pencolor, color) -> assoc (state, :pencolor, color)
 		(:setheading, heading) -> assoc (state, :heading, heading)
+		(:show) -> assoc (state, :visible?, true)
+		(:hide) -> assoc (state, :visible?, false)
 	}
 }
 
@@ -1396,6 +1408,7 @@ pkg Prelude {
 	gte? & math
 	heading & turtles
 	heading/vector & math
+	hideturtle! & turtles
 	home! & turtles
 	inc & math
 	inv & math
@@ -1465,6 +1478,7 @@ pkg Prelude {
 	set? & sets
 	setheading! & turtles
 	show & strings
+	showturtle! & turtles
 	sin & math
 	slice & lists tuples strings
 	some & values

src/ludus.janet

@@ -49,10 +49,11 @@
  (set (out :draw) (post :draw))
  (-> out j/encode string))
 
-(comment
+# (comment
-# (do
+(do
 (def source `
-butlast ([1, 2, 3])
+hideturtle! ()
+showturtle! ()
 `)
 (def out (-> source 
  ludus