diff --git a/src/__private__/__is_vector.scad b/src/__private__/__is_vector.scad
new file mode 100644
index 00000000..a4e9d880
--- /dev/null
+++ b/src/__private__/__is_vector.scad
@@ -0,0 +1 @@
+function __is_vector(value) = !(value >= "") && len(value) != undef;
\ No newline at end of file
diff --git a/src/cross_sections.scad b/src/cross_sections.scad
index 888ec9ad..964ba6e3 100644
--- a/src/cross_sections.scad
+++ b/src/cross_sections.scad
@@ -11,12 +11,14 @@
 *
 **/
 
+include <__private__/__is_vector.scad>;
+
 function cross_sections(shape_pts, path_pts, angles, twist = 0, scale = 1.0) =
     let(
         len_path_pts_minus_one = len(path_pts) - 1,
         sh_pts = len(shape_pts[0]) == 3 ? shape_pts : [for(p = shape_pts) [p[0], p[1], 0]],
         pth_pts = len(path_pts[0]) == 3 ? path_pts : [for(p = path_pts) [p[0], p[1], 0]],
-        scale_step_vt = len(scale) == 2 ? 
+        scale_step_vt = __is_vector(scale) ? 
             [(scale[0] - 1) / len_path_pts_minus_one, (scale[1] - 1) / len_path_pts_minus_one] :
             [(scale - 1) / len_path_pts_minus_one, (scale - 1) / len_path_pts_minus_one],
         scale_step_x = scale_step_vt[0],
diff --git a/src/helix.scad b/src/helix.scad
index c247a8ae..f6679e19 100644
--- a/src/helix.scad
+++ b/src/helix.scad
@@ -12,12 +12,14 @@
 *
 **/ 
 
+include <__private__/__is_vector.scad>;
 include <__private__/__frags.scad>;
 
 function helix(radius, levels, level_dist, vt_dir = "SPI_DOWN", rt_dir = "CT_CLK") = 
     let(
-        r1 = len(radius) == undef ? radius : radius[0],
-        r2 = len(radius) == undef ? radius : radius[1],
+        is_vt = __is_vector(radius),
+        r1 = is_vt ? radius[0] : radius,
+        r2 = is_vt ? radius[1] : radius,
         init_r = vt_dir == "SPI_DOWN" ? r2 : r1,
         _frags = __frags(init_r),
         h = level_dist * levels,
diff --git a/src/helix_extrude.scad b/src/helix_extrude.scad
index cd7fe200..a4729c3a 100644
--- a/src/helix_extrude.scad
+++ b/src/helix_extrude.scad
@@ -10,14 +10,16 @@
 *
 **/
 
+include <__private__/__is_vector.scad>;
 include <__private__/__frags.scad>;
 
 module helix_extrude(shape_pts, radius, levels, level_dist, 
                      vt_dir = "SPI_DOWN", rt_dir = "CT_CLK", 
                      twist = 0, scale = 1.0, triangles = "RADIAL") {
-
-    r1 = len(radius) == undef ? radius : radius[0];
-    r2 = len(radius) == undef ? radius : radius[1];
+                         
+    is_vt = __is_vector(radius);
+    r1 = is_vt ? radius[0] : radius;
+    r2 = is_vt ? radius[1] : radius;
     
     init_r = vt_dir == "SPI_DOWN" ? r2 : r1;
 
diff --git a/src/path_extrude.scad b/src/path_extrude.scad
index 6498e5c0..8370885c 100644
--- a/src/path_extrude.scad
+++ b/src/path_extrude.scad
@@ -13,6 +13,8 @@
 *
 **/
 
+include <__private__/__is_vector.scad>;
+
 module path_extrude(shape_pts, path_pts, triangles = "RADIAL", twist = 0, scale = 1.0, closed = false) {
 
     s_pts = to3d(shape_pts);
@@ -21,7 +23,7 @@ module path_extrude(shape_pts, path_pts, triangles = "RADIAL", twist = 0, scale
     len_path_pts = len(pth_pts);    
     len_path_pts_minus_one = len_path_pts - 1;     
 
-    scale_step_vt = len(scale) == 2 ? 
+    scale_step_vt = __is_vector(scale) ? 
         [(scale[0] - 1) / len_path_pts_minus_one, (scale[1] - 1) / len_path_pts_minus_one] :
         [(scale - 1) / len_path_pts_minus_one, (scale - 1) / len_path_pts_minus_one];
 
diff --git a/src/rounded_cube.scad b/src/rounded_cube.scad
index 1490d094..f23a3074 100644
--- a/src/rounded_cube.scad
+++ b/src/rounded_cube.scad
@@ -11,12 +11,14 @@
 *
 **/
 
+include <__private__/__is_vector.scad>;
 include <__private__/__frags.scad>;
 
 module rounded_cube(size, corner_r, center = false) {
-    x = len(size) == undef ? size : size[0];
-    y = len(size) == undef ? size : size[1];
-    z = len(size) == undef ? size : size[2];
+    is_vt = __is_vector(size);
+    x = is_vt ? size[0] : size;
+    y = is_vt ? size[1] : size;
+    z = is_vt ? size[2] : size;
 
     frags = __frags(corner_r);
 
diff --git a/src/rounded_square.scad b/src/rounded_square.scad
index 13aff21a..618ea658 100644
--- a/src/rounded_square.scad
+++ b/src/rounded_square.scad
@@ -11,6 +11,7 @@
 *
 **/
 
+include <__private__/__is_vector.scad>;
 include <__private__/__frags.scad>;
 
 module rounded_square(size, corner_r, center = false) {
@@ -21,8 +22,9 @@ module rounded_square(size, corner_r, center = false) {
 
     step_a = 360 / corner_frags;
  
-    x = len(size) == undef ? size : size[0];
-    y = len(size) == undef ? size : size[1];
+    is_vt = __is_vector(size);
+    x = is_vt ? size[0] : size;
+    y = is_vt ? size[1] : size;
 
     half_x = x / 2;
     half_y = y / 2;