Operator overloads for unary expressions

examples/operator_overloading.kl

@@ -1,14 +1,19 @@
 
-Vec3   :: struct;; x: F32; y: F32; z: F32
-"+" :: (a: Vec3, b: Vec3): Vec3 ;; return Vec3{a.x+b.x, a.y+b.y, a.z+b.z}
+Vec3 :: struct;; x: F32; y: F32; z: F32
 
+// We can define operator overloads for arbitrary types
+// these are just regular lambdas/functions
+"+"  :: (a: Vec3, b: Vec3): Vec3 ;; return {a.x+b.x, a.y+b.y, a.z+b.z}
+"-"  :: (a: Vec3, b: Vec3): Vec3 ;; return {a.x-b.x, a.y-b.y, a.z-b.z}
+"-"  :: (a: Vec3): Vec3          ;; return {-a.x, -a.y, -a.z}
 
 main :: (): int
   a := Vec3{1,1,1}
   b := Vec3{2,3,4}
   c := a + b
-  Assert(c.x == 3)
-  Assert(c.y == 4)
-  Assert(c.z == 5)
-
+  Assert(c.x == 3 && c.y == 4 && c.z == 5)
+  d := -c
+  Assert(d.x == -3 && d.y == -4 && d.z == -5)
+  e := c - d
+  Assert(e.x == 6 && e.y == 8 && e.z == 10)
   return 0