"999 is enough for anybody" triple-zero padding (#18)

When I hit 999 exercises, I will finally have reached the ultimate
state of soteriological release and no more exercises will be needed.
The cycle will be complete. All that will be left is perfect quietude,
freedom, and highest happiness.

exercises/040_pointers2.zig

@@ -0,0 +1,27 @@
+//
+// It's important to note that variable pointers and constant pointers
+// are different types.
+//
+// Given:
+//
+//     var foo: u8 = 5;
+//     const bar: u8 = 5;
+//
+// Then:
+//
+//     &foo is of type "*u8"
+//     &bar is of type "*const u8"
+//
+// You can always make a constant pointer to a variable, but you cannot
+// make a variable pointer to a constant. This sounds like a logic puzzle,
+// but it just means that once data is declared immutable, you can't
+// coerce it to a mutable type. It's a safety thing (to prevent mistakes).
+//
+const std = @import("std");
+
+pub fn main() void {
+    const a: u8 = 12;
+    const b: *u8 = &a; // fix this!
+
+    std.debug.print("a: {}, b: {}\n", .{ a, b.* });
+}