improve explanantions in labeled switch

exercises/108_labeled_switch.zig

@@ -1,15 +1,54 @@
 //
-// A labeled switch in zig allows the usage of continue and break
-// just like loops, these allow you to create very concise
-// Finite State Automata to represent state transitions
-//
-//      foo: switch (state) {
-//          1 => continue :foo 2,
-//          2 => continue :foo 3,
-//          3 => break :foo,
-//          4 => {},
-//         ...
-//     }
+// You've heard of while loops in exercises 011,012,013 and 014
+// You've also heard of switch expressions in exercises 030 and 31.
+// You've also seen how labels can be used in exercise 063.
+//
+// By combining while loops and switch statements with continue and break statements
+// one can create very concise State Machines.
+//
+// One such example would be:
+//
+//      pub fn main() void {
+//          var op: u8 = 1;
+//          while (true) {
+//              switch (op) {
+//                  1 => { op = 2; continue; },
+//                  2 => { op = 3; continue; },
+//                  3 => return,
+//                  4 => {},
+//              }
+//              break;
+//          }
+//      std.debug.print("This statement cannot be reached");
+//      }
+//
+// By combining all we've learned so far, we can now proceed with a labeled switch
+//
+// A labeled switch is some extra syntatic sugar, which comes with all sorts of
+// candy (performance benefits). Don't believe me? Directly to source https://github.com/ziglang/zig/pull/21367
+//
+// Here is the previous excerpt implemented as a labeled switch instead:
+//
+//      pub fn main() void {
+//          foo: switch (@as(u8, 1)) {
+//              1 => continue :foo 2,
+//              2 => continue :foo 3,
+//              3 => return,
+//              4 => {},
+//          }
+//          std.debug.print("This statement cannot be reached");
+//      }
+//
+// The flow of execution on this second case is:
+//  1. The switch starts with value '1';
+//  2. The switch evaluates to case '1' which in turn uses the continue statement
+//        to re-evaluate the labeled switch again, now providing the value '2';
+//  3. In the case '2' we repeat the same pattern as case '1'
+//        but instead the value to be evaluated is now '3';
+//  4. Finally we get to case '3', where we return from the function as a whole.
+//
+// Since step 4 or a break stament do not exist in this switch, the debug statement is
+// never executed
 //
 const std = @import("std");