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Sure. The book is a sort of resource for learning the programming language Scheme, where the authors will present an illustrative piece of code and discuss different aspects of its behavior in the form of a question-and-answer dialogue with the reader.
In this case, the authors are discussing how to perform numerical comparisons using only a simple set of basic procedures, and they've come up with a method that has a subtle error. The lines above encourage the reader to figure out if and why it's an error.
With computers, it's really easy to just have a half-baked idea, twiddle some bits, and watch things change, but sometimes the surface appearance of a change is not the whole story. Remembering to "think first, then try" helps me maintain the right discipline for really understanding what's going on in complex systems. Thinking first about my mental model of a situation prompts questions like this:
It's harder psychologically (and maybe too late) to ask those questions in retrospect if you try first, and then think, and if you skip asking them, then you'll suffer later.
This is a great reminder, and is not always easy advice to follow, especially if your edit-compile-run cycle tightens or collapses completely. I think there's a tricky balance between understanding something explicitly, which you can only do by training your model by thinking carefully, and understanding something intuitively, which is made much easier with tools like the ones I linked.
Do you have a sense for which kind of understanding is more useful in practice? I suspect that when I design or debug software I am making heavier use of System 1 thinking t... (read more)