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CS61A: The Structure and Interpretation of Computer Programs

129 points| curious16 | 2 years ago |inst.eecs.berkeley.edu

38 comments

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zackmorris|2 years ago

Funny story: I took Scheme around 1995 for my first college programming class at UIUC, and nobody told me that we could split our code up into separate lines of execution. So I turned in all of my assignments for the semester as a multi-page function composed of higher-order methods executed in one shot. My teacher must have stared at some of them dumfounded, because they all worked. Although remembering back, I don't think I was the only student doing that!

In the end, it helped me see that all programming is basically a spreadsheet and analogous to the STDIN/STDOUT stream processing of Unix executables. All of the stuff we think of as programming, like objects and classes, is basically hand waving to make problems/solutions supposedly fit in the human mind.

somewhat_drunk|2 years ago

>In the end, it helped me see that all programming is basically a spreadsheet and analogous to the STDIN/STDOUT stream processing of Unix executables. All of the stuff we think of as programming, like objects and classes, is basically hand waving to make problems/solutions supposedly fit in the human mind.

Holy shit Zack, I thought you didn't pay attention at Bayside???

Mind-blowing thought for my mind at this place and this time. Something that I intuited at some point but never made concrete by putting it into words. Thanks for sharing!

syngrog66|2 years ago

SICP is one of my favorite books on programming. Along with GEB and Levy's Hackers.

When I want to give a young person a headstart "sneak preview" taster into "our" culture -- or what I think our culture should be, on the intellectual plane, as an ideal, then I'm confident that these in particular can be stimulating little gems.

OK, fine fine: also HHGG as the 4th of my top 3. The first book (in its series) especially but the entire 5+ books of its increasingly misnamed trilogy.

And... Neuromancer. And Snow Crash. And Cryptonomicon. And...

jmort253|2 years ago

Cool! I was in the process of reading the JavaScript version. Converting the book to various languages will help spread the concepts in this book to a larger audience.

azangru|2 years ago

Oh wow! I didn't know js version existed! I'll go check it out.

vasili111|2 years ago

Anyone have experience reading both LISP and Python version of SICP? Does the Python version as good as LISP version?

dingosity|2 years ago

Kris Jenkins wrote this page about functional programming, which is the best quick explanation of why functional programming languages matter: http://blog.jenkster.com/2015/12/what-is-functional-programm...

And then you mix that with Larry Wall's famous quote: "Computer languages differ not so much in what they make possible, but in what they make easy."

So you mix these two references together and you get the idea that maybe Lisp and Scheme and ML make functional programming easy. Python, on the other hand, makes it easy to avoid the key feature of Lisp: separating concerns and managing complexity.

This doesn't mean Python is a bad language, and it doesn't mean you can't use python to craft programs in a functional style. But it's A LOT easier in Python for an inexperienced programmer to do things that Lisp and Scheme are trying to force you to avoid (by exposing unnecessary state to a function, conflating concerns and avoiding abstractions for manipulating complexity.)

I think this is why Scheme was originally chosen for SICP over contemporary languages like C or Modula-{2|3} or Bliss. It's simultaneously good for CS pedagogy and a small team can build decent, extendible, testable and debuggable programs with it.

gumby|2 years ago

Python isn’t as powerful as lisp so you end up standing on your head to do some of the things that are so straightforward in lisp.

I suppose using python might make it easier for some people to translate what they learned in class into their work, at least if that is in python.

Python has gobs of libraries so it’s easier to write complex programs that can benefit from that than it is to try the same in lisp.

soegaard|2 years ago

Just in case: use an editor with support for Scheme.

If you want something easy to install, try DrRacket.

- tab indents the current line

- cmd-I (or ctrl-I) will indent the entire buffer

- Press ] to insert a matching closer (an parenthesis, bracket or brace)

When you need it, install the `sicp` package to get the Henderson picture language (and more) used in the book.

alkonaut|2 years ago

Are there "conversions" for other languages as well? I know it's almost required reading for any software developer worth their salt, but I have several failed starts with the original version and have sworn to never have to read Lisp code. I get the gist. I get that Lisp elegantly represents the close tie between data and programs in a way that procedural programs never will, which is probably why it is chosen for the book. But no matter how perfectly suited for the task it is, I won't squint at lines ending in ))))) to try to see that meaning.

Zambyte|2 years ago

> I get that Lisp elegantly represents the close tie between data and programs in a way that procedural programs never will

Procedural is probably the best paradigm box to fit most Lisp in.

> I won't squint at lines ending in ))))) to try to see that meaning.

Nor do people who read and write Lisp. The indentation is really all that matters when reading Lisp. When writing Lisp, having your editor highlight matching parentheses is really the only feature you need to edit an expression that is deeply nested at the end like that. I bet your editor can already do that :)

shagie|2 years ago

In general, I would suggest that conversions to non-LISP languages (and that includes things like Ruby because people say "Ruby is my favorite LISP") makes pedagogical goals of teaching the theory difficult.

When I took my intro class in college, it was taught in Pascal. I had already been programming pascal (as taught by a chemist) in high school for a year or so. The first assignment which was Hello World I didn't even need to wake up in lectures for.

The second assignment... I didn't do quite so well. I had been using global variables and playing fast and loose with scope and passing variable parameters into procedures rather than using a function.

The thing was I already "knew" pascal and I had to unlearn what I knew before I could learn how to write pascal properly.

LISP (and Scheme and Clojure) work well in part because it always forces you to learn new concepts rather than having to unlearn what you did as a hobbiest before taking the class. The LISP family is unlikely to have been the choice language of a high schooler.

---

> But no matter how perfectly suited for the task it is, I won't squint at lines ending in ))))) to try to see that meaning.

When I took an AI class taught in LISP a few years later, the TA sent a joke email about how they had broken into some top secret code only to find it was all written in LISP. Due to the constraints of the mail system there they could only send the last {some number} characters.

))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))

noelwelsh|2 years ago

Reading Lisp isn't that onerous. For a start, the brackets (and particularly the closing brackets) are basically irrelevant. They help the computer parse the code but you can read it mostly based on indentation.

Anyway, there is a version in Javascript and the linked page has a textbook in Python.

kazinator|2 years ago

If you have reasons to believe that the ))))) is correct (or in any case you are not looking to convince yourself whether it is correct or not) then it just means "multiple expressions are being closed here, consistently with the indentation". There is no reason to stare at it.

tenebrisalietum|2 years ago

But you are OK looking at this?:

        }
       }

      }
     }

    }

BeetleB|2 years ago

Were you merely reading, or were you doing the exercises as well?

SICP was my first introduction to Scheme/Lisp - and not at a young age. Once I started doing the problems, reading it became trivial.

dingosity|2 years ago

or you could just use m-expressions. just an idea. you know. use the tools provided by the language.