<aside> 💡 One key mistake which I often make while designing my programs is that I don’t run the stub and function templates before I use them. If bugs are present within these lines of code, these bugs will be replicated in lines of code which are based on the stub + function templates.

So, the moral of the story is this: KEEP TESTING THE STUBS, TEMPLATES, AND EXAMPLES BY CONTINUALLY RUNNING THE PROGRAM OVER AND OVER AGAIN WHILE YOU’RE DESIGNING THE PROGRAM. It’ll save a lot of your time (which you would otherwise spend debugging) in the long run.

</aside>

Prelude: Why are templates important?

• Templates break the processes of design down to steps in a process, not pieces of a solution.
• Templates help you understand how to solve difficult problems with programs through an understanding of such programs’ basic structure.
  • e.g. Given that you know you need to define data at a certain area in the program, the HtDD template lays out the structure of what you need to write in order to complete the data definition. The same goes with defining functions with HtDF and constructing interactive programs with big-bang.
• We want to be able to look at the domain analysis then look at the code and understand where each part of the analysis shows up in the code. This is known as traceability.

How to Design Worlds (HtDW)

• The HtDW recipe is a process for the systematic construction of interactive programs.

• It comprises of 2 parts:

  • a. Domain analysis (do this on a piece of paper)
  • b. Developing code based on the analysis

• The structure of the program mirrors the structure of the analysis.

• Since the analysis is a model of the program, it becomes easy to make changes to the program once the analysis is updated with those changes.

This ability to work on programs by reasoning about them at a model level is one of the things that really separates program designers for people who write code that just happens to work.