Merge branch 'jeroenrnl-VariableNamesWithDigitsDeprecated'

Change names of variables from `2a` and `2c` to `ax2` (a times 2) and
`cx2`, because variable names starting with a digit are deprecated in
OpenSCAD.

CHANGELOG.md

@@ -3,6 +3,15 @@
 This changelog is generated by `changelog.py` using manually added semantic version tags to classify commits as breaking changes, additions or fixes.
 
 
+#### [v21.35.3](https://github.com/nophead/NopSCADlib/releases/tag/v21.35.3 "show release") Fixes [...](https://github.com/nophead/NopSCADlib/compare/v21.35.2...v21.35.3 "diff with v21.35.2")
+*   2025-03-27 [`9f9aa67`](https://github.com/nophead/NopSCADlib/commit/9f9aa6723eff9b7439e17758406e9f8e409828ee "show commit") [C.P.](# "Chris Palmer") Third attempt to fix dimension image.
+
+#### [v21.35.2](https://github.com/nophead/NopSCADlib/releases/tag/v21.35.2 "show release") Fixes [...](https://github.com/nophead/NopSCADlib/compare/v21.35.1...v21.35.2 "diff with v21.35.1")
+*   2025-03-27 [`6b6704b`](https://github.com/nophead/NopSCADlib/commit/6b6704b823291119697bf4993eddb3f2e6873875 "show commit") [C.P.](# "Chris Palmer") Second attempt to fix dimension image.
+
+#### [v21.35.1](https://github.com/nophead/NopSCADlib/releases/tag/v21.35.1 "show release") Fixes [...](https://github.com/nophead/NopSCADlib/compare/v21.35.0...v21.35.1 "diff with v21.35.0")
+*   2025-03-27 [`117fb62`](https://github.com/nophead/NopSCADlib/commit/117fb626e7023ca92339947a0f84a8aee5c6429e "show commit") [C.P.](# "Chris Palmer") Fixed dimension example image address.
+
 ### [v21.35.0](https://github.com/nophead/NopSCADlib/releases/tag/v21.35.0 "show release") Additions [...](https://github.com/nophead/NopSCADlib/compare/v21.34.0...v21.35.0 "diff with v21.34.0")
 *   2025-03-27 [`6dc8204`](https://github.com/nophead/NopSCADlib/commit/6dc82045fffeca383381724abb6d70d7025b2ae5 "show commit") [C.P.](# "Chris Palmer") Shortened the module comments by factoring out the parameter descriptions.
 Added the nut example picture.

readme.md

@@ -7253,7 +7253,7 @@ allows flexible positioning of the motors.
 ## Dimension
 Modules for adding dimensions to assembly views.
 
-<img src="https://github.com/nophead/NopSCADlib/raw/master/docs/sliding_t_nut.png" width="500", height="378">
+![](docs/sliding_t_nut_small.png)
 
 * If `text` is empty, will display the measured distance.
 * `offset` will determine how much space is between the measured point and the dimension.

utils/dimension.scad

@@ -20,7 +20,7 @@
 //
 //! Modules for adding dimensions to assembly views.
 //!
-//! <img src="https://github.com/nophead/NopSCADlib/raw/master/docs/sliding_t_nut.png" width="500", height="378">
+//! ![](docs/sliding_t_nut_small.png)
 //!
 //! * If `text` is empty, will display the measured distance.
 //! * `offset` will determine how much space is between the measured point and the dimension.

utils/maths.scad

@@ -164,13 +164,13 @@ function xor(a,b) = (a && !b) || (!a && b);     //! Logical exclusive OR
 function cuberoot(x)= sign(x)*abs(x)^(1/3);
 
 function quadratic_real_roots(a, b, c) =        //! Returns real roots of a quadratic equation, biggest first. Returns empty list if no real roots
-    let(2a = 2 * a,
-        2c = 2 * c,
-        det = b^2 - 2a * 2c
+    let(ax2 = 2 * a,
+        cx2 = 2 * c,
+        det = b^2 - ax2 * cx2
     ) det < 0 ? [] :
         let(r = sqrt(det),
-            x1 = b < 0 ? 2c / (-b + r) : (-b - r) / 2a,
-            x2 = b < 0 ? (-b + r) / 2a : 2c / (-b - r)
+            x1 = b < 0 ? cx2 / (-b + r) : (-b - r) / ax2,
+            x2 = b < 0 ? (-b + r) / ax2 : cx2 / (-b - r)
         ) [x2, x1];
 
 function cubic_real_roots(a, b, c, d) = //! Returns real roots of cubic equation