add lsystem2.scad

src/experimental/_impl/_lsystem2_impl.scad

@@ -0,0 +1,65 @@
+use <experimental/assoc_lookup.scad>;
+use <turtle/turtle2d.scad>;
+
+// It doesn't use recursion to avoid recursion error. 
+function _join(strs) = 
+    let(leng = len(strs))
+    [for(i = 0, s = strs[0]; i < leng; i = i + 1, s = str(s, strs[i])) s][leng - 1];
+
+function _produce1(base, rule) = _join([
+    for(c = base) 
+    let(v = assoc_lookup(rule, c))
+    is_undef(v) ? c : v
+]);
+
+function _produce(base, rule, n, i = 0) =
+    i == n ? base : _produce(_produce1(base, rule), rule, n, i + 1);
+    
+function produce(rule, n) =
+    _produce(assoc_lookup(rule, "S"), rule, n);
+
+function cmd(symbol, args) =
+    symbol == "F" ? ["forward", args[0]] :
+    symbol == "M" ? ["move", args[0]] :
+    symbol == "+" ? ["turn", args[1]] :
+    symbol == "-" ? ["turn", -args[1]] : 
+    symbol == "[" ? ["push"] :
+    symbol == "]" ? ["pop"] : [];
+    
+function _fd_if_mv(cmd) = 
+    cmd == "move" ? "forward" : cmd;
+
+function _next_stack(t, cmd, stack) = 
+    cmd[0] == "push" ? concat([t], stack) :
+    let(leng = len(stack))
+    cmd[0] == "pop" ? 
+            (leng > 1 ? [for(i = [1:leng - 1]) stack[i]] : []) :
+            stack;
+
+function _next_t1(t1, t2, cmd, stack) = 
+    cmd[0] == "push" ? t1 : 
+    cmd[0] == "pop" ? stack[0] : t2; 
+    
+function _next_t2(t, cmd) = 
+    is_undef(cmd) || cmd[0] == "push" || cmd[0] == "pop" ? t : turtle2d(_fd_if_mv(cmd[0]), t, cmd[1]);
+
+// It doesn't use recursion to avoid recursion error.    
+function _lines(t, cmds) = 
+    let(leng = len(cmds))
+    [
+        for(
+            i = 0,
+            stack = [],            
+            t1 = t, 
+            t2 = _next_t2(t1, cmds[i]);
+            
+            i < leng; 
+            
+            t1 = _next_t1(t1, t2, cmds[i], stack), 
+            stack = _next_stack(t1, cmds[i], stack),
+            i = i + 1, 
+            t2 = _next_t2(t1, cmds[i])
+        )
+        if(cmds[i][0] != "move" && cmds[i][0] != "push" && cmds[i][0] != "pop")
+            [turtle2d("pt", t1), turtle2d("pt", t2)]
+    ];

src/experimental/lsystem2.scad

@@ -0,0 +1,16 @@
+use <experimental/_impl/_lsystem2_impl.scad>;
+use <turtle/turtle2d.scad>;
+
+function lsystem2(rule, n, angle, leng = 1, heading = 0, start_pt = [0, 0]) =
+    let(
+        produced = produce(rule, n),
+        cmds = [
+            for(s = produced) 
+            let(c = cmd(s, [leng, angle]))
+            if(c != []) c
+        ]
+    )
+    _lines(
+        turtle2d("create", start_pt[0], start_pt[0], heading), 
+        cmds
+    );