use built-in is_undef

src/along_with.scad

@@ -20,14 +20,14 @@ module along_with(points, angles, twist = 0, scale = 1.0, method = "AXIS_ANGLE")
     leng_points_minus_one = leng_points - 1;
     twist_step_a = twist / leng_points;
 
-    angles_defined = angles != undef;
+    angles_defined = !is_undef(angles);
 
     scale_step_vt = is_num(scale) ? 
         scale_step() :
         [
             (scale[0] - 1) / leng_points_minus_one, 
             (scale[1] - 1) / leng_points_minus_one,
-            scale[2] == undef ? 0 : (scale[2] - 1) / leng_points_minus_one
+            is_undef(scale[2]) ? 0 : (scale[2] - 1) / leng_points_minus_one
         ]; 
 
 

src/circle_path.scad

@@ -14,7 +14,7 @@ function circle_path(radius, n) =
     let(
         _frags = __frags(radius),
         step_a = 360 / _frags,
-        end_a = 360 - step_a * ((n == undef || n > _frags) ? 1 : _frags - n + 1)
+        end_a = 360 - step_a * ((is_undef(n) || n > _frags) ? 1 : _frags - n + 1)
     )
     [
         for(a = [0 : step_a : end_a]) 

src/ellipse_extrude.scad

@@ -9,7 +9,7 @@
 **/
 
 module ellipse_extrude(semi_minor_axis, height, center = false, convexity = 10, twist = 0, slices = 20) {
-    h = height == undef ? semi_minor_axis : (
+    h = is_undef(height) ? semi_minor_axis : (
         // `semi_minor_axis` is always equal to or greater than `height`.
         height > semi_minor_axis ? semi_minor_axis : height
     );

src/m_rotation.scad

@@ -78,4 +78,4 @@ function m_rotation(a, v) =
         [0, 1, 0, 0],
         [0, 0, 1, 0],
         [0, 0, 0, 1]
-    ] : (v == undef ? _xyz_rotation(a) : _q_rotation(a, v));
+    ] : (is_undef(v) ? _xyz_rotation(a) : _q_rotation(a, v));

src/path_extrude.scad

@@ -45,7 +45,7 @@ module path_extrude(shape_pts, path_pts, triangles = "SOLID", twist = 0, scale =
             [
                 (scale[0] - 1) / len_path_pts_minus_one, 
                 (scale[1] - 1) / len_path_pts_minus_one,
-                scale[2] == undef ? 0 : (scale[2] - 1) / len_path_pts_minus_one
+                is_undef(scale[2]) ? 0 : (scale[2] - 1) / len_path_pts_minus_one
             ];   
 
         // get rotation matrice for sections

src/rotate_p.scad

@@ -86,4 +86,4 @@ function _q_rotate_p(p, a, v) =
         );
 
 function rotate_p(point, a, v) =
-    v == undef ? _rotate_p(point, a) : _q_rotate_p(point, a, v);
+    is_undef(v) ? _rotate_p(point, a) : _q_rotate_p(point, a, v);

src/sub_str.scad

@@ -9,7 +9,7 @@
 **/ 
 
 function sub_str(t, begin, end, result = "") =
-    end == undef ? sub_str(t, begin, len(t)) : (
+    is_undef(end) ? sub_str(t, begin, len(t)) : (
         begin == end ? result : sub_str(t, begin + 1, end, str(result, t[begin]))
     );
     

src/turtle2d.scad

@@ -34,7 +34,7 @@ function _turtle2d_three_args_command(cmd, arg1, arg2, arg3) =
     cmd == "create" ? _turtle2d_turtle(arg1, arg2, arg3) : _turtle2d_two_args_command(cmd, arg1, arg2);
 
 function _turtle2d_two_args_command(cmd, arg1, arg2) =
-    arg2 == undef ? _turtle2d_one_arg_command(cmd, arg1) : (
+    is_undef(arg2) ? _turtle2d_one_arg_command(cmd, arg1) : (
         cmd == "pt" ? _turtle2d_set_point(arg1, arg2) : (
             cmd == "x" ? _turtle2d_set_x(arg1, arg2) : (
                 cmd == "y" ? _turtle2d_set_y(arg1, arg2) : (

src/turtle3d.scad

@@ -122,8 +122,8 @@ function _turtle3d_zu_turn(turtle, a) =
     );
 
 function _turtle3d_create_cmd(arg1, arg2) = 
-    (arg1 == undef && arg2 == undef) ? _turtle3d_create_default() : (
-        (arg1 != undef && arg2 != undef) ? _turtle3d_create(arg1, arg2) : undef
+    (is_undef(arg1) && is_undef(arg2)) ? _turtle3d_create_default() : (
+        (!is_undef(arg1) && !is_undef(arg2)) ? _turtle3d_create(arg1, arg2) : undef
     );
     
 function _turtle3d_chain_move(cmd, arg1, arg2) =