Add example for simple functions.

examples/Functions/functions.scad

@@ -0,0 +1,35 @@
+echo(version=version());
+
+// Functions can be defined to simplify code using lots of
+// calculations.
+
+// Simple example with a single function argument (which should
+// be a number) and returning a number calculated based on that.
+function f(x) = 0.5 * x + 1;
+
+color("red")
+    for (a = [ -100 : 5 : 100 ])
+        translate([a, f(a), 0]) cube(2, center = true);
+
+// Functions can call other functions and return complex values
+// too. In this case a 3 element vector is returned which can
+// be used as point in 3D space or as vector (in the mathematical
+// meaning) for translations and other transformations.
+function g(x) = [ 5 * x + 20, f(x) * f(x) - 50, 0 ];
+
+color("green")
+    for (a = [ -200 : 10 : 200 ])
+        translate(g(a / 8)) sphere(1);
+
+
+
+// Written in 2015 by Torsten Paul <Torsten.Paul@gmx.de>
+//
+// To the extent possible under law, the author(s) have dedicated all
+// copyright and related and neighboring rights to this software to the
+// public domain worldwide. This software is distributed without any
+// warranty.
+//
+// You should have received a copy of the CC0 Public Domain
+// Dedication along with this software.
+// If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.