Some ported examples in algebra mode

examples/circuit_board_algebra.py

@@ -0,0 +1,21 @@
+from itertools import product
+
+from alg123d import *
+
+pcb = Rectangle(70, 30)
+
+for loc in GridLocations(60, 20, 2, 2):
+    pcb -= loc * Circle(2)
+
+for i, y in product(range(65 // 5), (-15, -10, 10, 15)):
+    x = i * 5 - 30
+    pcb -= Pos(x, y) * Circle(1)
+
+for x, i in product((30, 35), range(30 // 5 - 1)):
+    y = i * 5 - 10
+    pcb -= Pos(x, y) * Circle(1)
+
+pcb = extrude(pcb, 3)
+
+if "show_object" in locals():
+    show(pcb)