The rule of three suggests that if you encounter the same pattern for the third time in your code, you should refactor it into a reusable abstraction. The same thing applies in programming language theory. When you find that you are doing the same thing for the third time, it is probably a good idea to stop and think - is there a general pattern? Figure 1. Auto-completion list showing possible operations in The Gamma In my PhD thesis on context-aware computations, I did exactly this. When we realised th[...]