it-ebooks - Programming Languages Application and Interpretation

From: Programming Languages: Application and Interpretation

Please watch thevideo on YouTube.Someday there will be a textual description here instead.

Unlike some other textbooks, this one does not follow a top-downnarrative. Rather it has the flow of a conversation, withbacktracking. We will often build up programs incrementally, just asa pair of programmers would. We will include mistakes, not because Idont know the answer, but because this is the best way for youto learn . Including mistakes makes it impossible for you to readpassively: you must instead engage with the material, because you cannever be sure of the veracity of what youre reading.

At the end, youll always get to the right answer. However, thisnon-linear path is more frustrating in the short term (you will oftenbe tempted to say, Just tell me the answer, already!), and itmakes the book a poor reference guide (you cant open up to a randompage and be sure what it says is correct). However, that feeling offrustration is the sensation of learning. I dont know of a wayaround it.

At various points you will encounter this:

This is an exercise. Do try it.

This is a traditional textbook exercise. Its something you need todo on your own. If youre using this book as part of a course, thismay very well have been assigned as homework. In contrast, you willalso find exercise-like questions that look like this:

Theres an activity here! Do you see it?

When you get to one of these, stop . Read, think, and formulatean answer before you proceed. You must do this because this isactually an exercise , but the answer is already in thebookmost often in the text immediately following (i.e., in the partyoure reading right now)or is something you can determine foryourself by running a program. If you just read on, youll see theanswer without having thought about it (or not see it at all, if theinstructions are to run a program), so you will get to neither (a)test your knowledge, nor (b) improve your intuitions. In other words,these are additional, explicit attempts to encourage active learning.Ultimately, however, I can only encourage it; its up to you topractice it.

The type names can even be used recursively, as we will seerepeatedly in this book (for instance, ).