add comment

src/experimental/lsystem2.scad

@@ -1,6 +1,17 @@
 use <experimental/_impl/_lsystem2_impl.scad>;
 use <turtle/turtle2d.scad>;
 
+/*
+
+   F  Move forward and draw line
+   f  Move forward without drawing a line
+   +  Turn left
+   -  Turn right
+   [  Push current turtle state onto stack
+   ]  Pop current turtle state from the stack
+
+*/
+
 function lsystem2(axiom, rules, n, angle, leng = 1, heading = 0, start = [0, 0], forward_chars = "F", rules_pr) =
     let(
         derived = _lsystem2_derive(axiom, rules, n, rules_pr),

src/experimental/lsystem3.scad

@@ -1,6 +1,17 @@
 use <experimental/_impl/_lsystem3_impl.scad>;
 use <turtle/turtle3d.scad>;
 
+/*
+
+   F  Move forward and draw line
+   f  Move forward without drawing a line
+   +  Turn left
+   -  Turn right
+   [  Push current turtle state onto stack
+   ]  Pop current turtle state from the stack
+
+*/
+
 function lsystem3(axiom, rules, n, angle, leng = 1, heading = 0, start = [0, 0, 0], forward_chars = "F", rules_pr) =
     let(
         derived = _lsystem3_derive(axiom, rules, n, rules_pr),