[Index of Lectures]

[ L01 L02 L03 L04 L05 L06 L07 L08 L09 L10 L11 L12 L13 L14 L15 L16 L17 L18 L19 L20 L21 L22 L23 ]

Lecture 02—How to Design Functions (HtDF recipe)

Before Lecture

Before beginning Lecture 02 you should have worked through all sections of Module 1a (Beginning Student Language). Being comfortable with the foundational BSL material will enable you to focus on the new material in this module. Remember that when we say work through what we mean is that you should:

• Do some combination of stopping the videos and working ahead, then checking yourself against the video; or typing along with the video.
• Answer all of the edX questions, and when you get one wrong take the time to understand what is the correct answer and why.
• Remember that no one ever got better at program design (or tennis, or skiing, or playing the violin, or drawing or...) by watching someone else do it.

During Lecture

This lecture introduces the most important element of the course—the How to Design Functions (HtDF) recipe. This is a systematic process for designing a well-thought out, consistent, and well tested function. By the end of the course you will use this recipe hundreds of times, and each time you will learn a little more about it.

By the end of the lecture—including the post-lecture work—you should be able to:

• Use the HtDF recipe to systematically design simple functions operating on numbers, strings, and images.
• Complete all parts of the HtDF recipe for such functions.
• Use the metadata tags (@htdf, @signature, @template-origin and @template) in the design.
• Begin to be comfortable with the fact that program design often involves having to find and use new resources.
• Begin to be comfortable with the fact that program design inherently involves making and then fixing mistakes.

The starter file for this lecture is:

• m01-htdf-starter.rkt

After Lecture

Here is the solution file for this lecture. (Don't look at it until you have tried to solve all the problems yourself!)

• m01-htdf-solution.rkt

Here's how you should approach reviewing what we have covered so far. You will probably have done a lot of what is below already, so incorporate what you have already done into how you adopt the plan below.

• First redo all the problems from today's lecture. Do that BEFORE you look at the posted solutions above.
• Also work through any problems we did not complete in lecture.
• Then work through the videos in 1b HtDF as need be. Definitely work through the HtDF slow video, and then work through the other example videos as you feel you need to so that you are comfortable with HtDF. Try getting the starter and working through the problem on your own, and then when you don't know what to do watch the video up to that point to help you. Pause and restart a lot as you get help and then work through pieces on your own! (Be sure to answer all the questions in all the sections though.)
• Finally work the practice problems from the Problem Bank. You can get help on these in office/DLC hours from an instructor or a TA (all office hours info is on the Schedule page or post a question on Piazza.
• Then you will be ready to complete problem set 1. Be sure you complete problem set 1 by the deadline.

You will be responsible for knowing all material covered in the Beginning Student Language (1a) and How to Design Functions (1b) edX modules. That means all the sections, the videos and all the questions interspersed in those videos.

And always remember, it's a learn by doing discipline. A prior learner said:

This is a bit like learning to make bread, or carve wood, or fold origami. Knowing what to do and how to do it comes through practice, practice, and more practice. Because we'll constantly need to re-apply our gained knowledge in different circumstances, practice is the only way to really gain a deep understanding of how these concepts work for a variety of problems.

Finally, quick notes: Any time you have a question about the course, it is likely answered in one of two places: on Piazza or in the Syllabus. So, go back to the Discussion board and the Syllabus regularly!

Be sure to complete the before lecture section of Lecture 3 before that lecture.