refactoed path_extend to shape_path_extend

README.md

@@ -38,7 +38,6 @@ Too many dependencies? Because OpenSCAD doesn't provide namespace management, I
 	- [hull_polyline2d](https://openhome.cc/eGossip/OpenSCAD/lib-hull_polyline2d.html)
 	- [hexagons](https://openhome.cc/eGossip/OpenSCAD/lib-hexagons.html)
 	- [polytransversals](https://openhome.cc/eGossip/OpenSCAD/lib-polytransversals.html)
-	- [path_extend](https://openhome.cc/eGossip/OpenSCAD/lib-path_extend.html)
 
 - 3D
 	- [rounded_cube](https://openhome.cc/eGossip/OpenSCAD/lib-rounded_cube.html)
@@ -88,6 +87,7 @@ Too many dependencies? Because OpenSCAD doesn't provide namespace management, I
 	- [shape_cyclicpolygon](https://openhome.cc/eGossip/OpenSCAD/lib-shape_cyclicpolygon.html)
     - [shape_pentagram](https://openhome.cc/eGossip/OpenSCAD/lib-shape_pentagram.html)	
 	- [shape_superformula](https://openhome.cc/eGossip/OpenSCAD/lib-shape_superformula.html)
+	- [shape_path_extend](https://openhome.cc/eGossip/OpenSCAD/lib-shape_path_extend.html)		
 
 - 2D Shape Extrusion
 	- [path_extrude](https://openhome.cc/eGossip/OpenSCAD/lib-path_extrude.html)

docs/lib-shape_path_extend.md

@@ -1,11 +1,11 @@
-# path_extend
+# shape_path_extend
 
-It extends a 2D stroke along a path. This module is suitable for a path created by a continuous function. 
+It extends a 2D stroke along a path to create a 2D shape. This module is suitable for a path created by a continuous function. The returned points can be used with xxx_extrude modules of dotSCAD. The shape points can be also used with the built-in polygon module.
-
-It depends on the rotate_p function and the polytransversals module. Remember to include "rotate_p.scad" and "polytransversals.scad".
 
 When using this module, you should use points to represent the 2D stroke. 
 
+It depends on the `rotate_p` function. Remember to include "rotate_p.scad" and "polytransversals.scad".
+
 ## Parameters
 
 - `stroke_pts` : A list of points represent a stroke. See the example below.
@@ -16,8 +16,7 @@ When using this module, you should use points to represent the 2D stroke.
 ## Examples
 
 	include <rotate_p.scad>;
-	include <polytransversals.scad>;
+	include <shape_path_extend.scad>;
-	include <path_extend.scad>;
 	include <circle_path.scad>;
 	include <archimedean_spiral.scad>;
 	
@@ -25,7 +24,10 @@ When using this module, you should use points to represent the 2D stroke.
 	
 	stroke1 = [[-5, 2.5], [-2.5, 0], [0, 2.5], [2.5, 0], [5, 2.5]];
 	path_pts1 = circle_path(50, 60);
-	path_extend(stroke1, path_pts1);
+    polygon(
+	    shape_path_extend(stroke1, path_pts1)
+    );
+    
 	
 	stroke2 = [[-4, 0], [0, 4], [4, 0]];
 	pts_angles = archimedean_spiral(
@@ -36,9 +38,11 @@ When using this module, you should use points to represent the 2D stroke.
 	); 
 	
 	translate([120, 0, 0]) 
-	    path_extend(
+	    polygon(
-	        stroke2, 
+            shape_path_extend(
-	        [for(pa = pts_angles) pa[0]]
+	            stroke2, 
-	    );
+	            [for(pa = pts_angles) pa[0]]
+	        )
+        );
 
-![path_extend](images/lib-path_extend-1.JPG)
+![path_extend](images/lib-shape_path_extend-1.JPG)

src/path_extend.scad

@@ -1,71 +0,0 @@
-/**
-* path_extend.scad
-*
-* It extends a 2D stroke along a path. 
-* This module is suitable for a path created by a continuous function.
-* It depends on the rotate_p function and the polytransversals module. 
-* Remember to include "rotate_p.scad" and "polytransversals.scad".
-*
-* @copyright Justin Lin, 2017
-* @license https://opensource.org/licenses/lgpl-3.0.html
-*
-* @see https://openhome.cc/eGossip/OpenSCAD/lib-path_extend.html
-*
-**/
-
-include <__private__/__to3d.scad>;
-include <__private__/__length_between.scad>;
-
-module path_extend(stroke_pts, path_pts, scale = 1.0, closed = false) {
-
-    function az(p1, p2) = 
-        let(
-            x1 = p1[0],
-            y1 = p1[1],
-            x2 = p2[0],
-            y2 = p2[1]
-        ) -90 + atan2((y2 - y1), (x2 - x1));
-    
-    leng_path_pts = len(path_pts);
-
-    scale_step = (scale - 1) / (leng_path_pts - 1);
-
-    function first_stroke() =
-        let(
-            p1 = path_pts[0],
-            p2 = path_pts[1],
-            a = az(p1, p2)
-        )
-        [
-            for(p = stroke_pts)
-                rotate_p(p, a) + p1
-        ];    
-    
-    function stroke(p1, p2, i) =
-        let(
-            leng = __length_between(__to3d(p1), __to3d(p2)),
-            a = az(p1, p2)
-        )
-        [
-            for(p = stroke_pts)
-                rotate_p(p * (1 + scale_step * i) + [0, leng], a) + p1
-        ];
-        
-    function path_extend_inner(index) =
-        index == leng_path_pts ? [] :
-            concat(
-               [stroke(path_pts[index - 1], path_pts[index], index)],
-               path_extend_inner(index + 1)
-           );
-
-    if(closed && path_pts[0] == path_pts[leng_path_pts - 1]) {
-        strokes = path_extend_inner(1);
-        polytransversals(
-            concat(strokes, [strokes[0]])
-        );
-    } else {
-        polytransversals(
-            concat([first_stroke()], path_extend_inner(1))
-        );
-    }
-}

src/shape_path_extend.scad

@@ -0,0 +1,82 @@
+/**
+* shape_path_extend.scad
+*
+* It extends a 2D stroke along a path. 
+* This module is suitable for a path created by a continuous function.
+* It depends on the rotate_p function and the polytransversals module. 
+* Remember to include "rotate_p.scad" and "polytransversals.scad".
+*
+* @copyright Justin Lin, 2017
+* @license https://opensource.org/licenses/lgpl-3.0.html
+*
+* @see https://openhome.cc/eGossip/OpenSCAD/lib-path_extend.html
+*
+**/
+
+include <__private__/__to3d.scad>;
+include <__private__/__length_between.scad>;
+include <__private__/__polytransversals.scad>;
+include <__private__/__reverse.scad>;
+
+function _shape_path_extend_az(p1, p2) = 
+    let(
+        x1 = p1[0],
+        y1 = p1[1],
+        x2 = p2[0],
+        y2 = p2[1]
+    ) -90 + atan2((y2 - y1), (x2 - x1));
+
+function _shape_path_first_stroke(stroke_pts, path_pts) =
+    let(
+        p1 = path_pts[0],
+        p2 = path_pts[1],
+        a = _shape_path_extend_az(p1, p2)
+    )
+    [
+        for(p = stroke_pts)
+            rotate_p(p, a) + p1
+    ];    
+
+function _shape_path_extend_stroke(stroke_pts, p1, p2, scale_step, i) =
+    let(
+        leng = __length_between(__to3d(p1), __to3d(p2)),
+        a = _shape_path_extend_az(p1, p2)
+    )
+    [
+        for(p = stroke_pts)
+            rotate_p(p * (1 + scale_step * i) + [0, leng], a) + p1
+    ];
+    
+function _shape_path_extend_inner(stroke_pts, path_pts, leng_path_pts, scale_step, index) =
+    index == leng_path_pts ? [] :
+        concat(
+            [
+                _shape_path_extend_stroke(
+                    stroke_pts, 
+                    path_pts[index - 1], 
+                    path_pts[index], 
+                    scale_step, 
+                    index
+                )
+            ],
+            _shape_path_extend_inner(
+                stroke_pts, 
+                path_pts, 
+                leng_path_pts, 
+                scale_step, 
+                index + 1
+            )
+        );
+
+function shape_path_extend(stroke_pts, path_pts, scale = 1.0, closed = false) =
+    let(
+        leng_path_pts = len(path_pts),
+        scale_step = (scale - 1) / (leng_path_pts - 1),
+        strokes = _shape_path_extend_inner(stroke_pts, path_pts, leng_path_pts, scale_step, 1)        
+    )
+    closed && path_pts[0] == path_pts[leng_path_pts - 1] ? 
+        __polytransversals(concat(strokes, [strokes[0]])) : 
+        __polytransversals(
+            concat([_shape_path_first_stroke(stroke_pts, path_pts)], strokes)
+        );
+