Composing Programs in Python, SICP Style | Hacker News Reader

Composing Programs in Python, SICP Style

composingprograms.com

244 pointsphilonoist17 comments

This is the textbook used for the introductory CS course (CS61A) at UC Berkeley. The course material is available at http://cs61a.org/fa18 (The course uses Python 3, Scheme, and SQL).

There are some neat projects (students build a Scheme interpreter and implement game logic as part of the projects)

Previous Hacker News Discussions (from which I’ve copied my comment)

https://news.ycombinator.com/item?id=11465234 https://news.ycombinator.com/item?id=3491142 https://news.ycombinator.com/item?id=3141996

Thanks for linking this, I'm currently working on designing an introductory python course. What background are students expected to have for CS61A? Is it expected to be students first introduction to python?

no background needed

Huh, I already thought this was suspicious reading the title, as Python does not have in-built TCO and indeed, https://composingprograms.com/pages/17-recursive-functions.h... does not even mention Stackoverflow errors and neither does it introduce a decorator to avoid them. Under these conditions however, it is impossible to compose programs "SICP Style".

None of the examples there in that section are tail recursive anyway. It has one example of a while loop for iteration.

Makes "SICP Style" seem like overselling it a bit.

When I worked through SICP in the 80s it was with XLisp on MS-DOS. XLisp didn't optimize tail recursion, and I had well under a megabyte, but this turned out to be a problem only once or twice, and ad-hoc hacks were enough then. (OTOH the system didn't have an only 1000-deep call-stack limit by default, either.)

It's true that this'd be more of a problem for real-world work.

They introduce both a traditional factorial function and a naive Fibonacci function - it seems likely most enterprising students will overflow the stack.

Odd that they don't (from a quick skim) seem to mention it at all? When they do hand wave a bit around stack frames (call trees)?

A naive fib(n) only needs stack depth of about n -- it takes a long time but doesn't need to go very deep.

You're right about Fibonacci - a naive fib(1000) takes a long time to eventually overflow the stack in python. But fact(1000) quickly crashes. Which is a shame as python has a full(?) number tower and has no problem calculating 1000!

People who find this interesting might find this answer of mine on stackoverflow interesting as well: https://stackoverflow.com/a/44729275/1163490

Great effort. I cannot find exercises? Do authors plan on adding those?

Very nice formatting for the content but it feels like it's missing three chapters on category theory and two chapters each on the AST module and the `compile` builtin after that last chapter on recursion.

perhaps occluded since this is focused on introductory computer science students?

It already has a chapter on MapReduce, which is making a few assumptions about where the student is going, whereas teaching category theory is appropriate for where the student is.

Which parts of the course would you drop or abreviate, in order to make time for these?

Very tough question.

Personally I'd lengthen the course with a Section "1.5" on the raw math topics being dealt with (Set Theory and Category Theory) plus ones the student will certainly bump into if they ever find themselves having to deploy MapReduce in production...

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