8 ms·

SICP in Clojure

132 points by MattF 11y ago

bogomipz 11y ago
This is awesome! I would love to see this span the whole SICP book. There was a kickstarter campaign for something called SICP Distilled, a while back. However it requires your github login which seemed kind of sketchy and also none of the content works anyway - http://www.sicpdistilled.com/ http://www.sicpdistilled.com/. Maybe someone else knows more? Anyway I look forward to seeing more chapters on your blog.
vqc 11y ago
This is exciting; I've been looking forward to doing this exact thing myself. Some more solutions can be found at https://github.com/gregsexton/SICP-Clojure https://github.com/gregsexton/SICP-Clojure
neoncontrails 11y ago
I've been feeling the past few weeks the repeated impact of hitting a wall. Programming was starting to feel like grinding. I felt wistful for SICP, when programming was full of big ideas and elegant new approaches to problems my unprincipled brain's first instinct was to clobber by brute force -- and learned, quickly, in Scheme, it's hard to be artless. It is, I think, harder code gracelessly in Scheme than to code with grace: it has a way of bending your ideas to a form. I think that's my main complaint with Python. In Python, exactly the opposite is true: it doesn't force you to think overly hard about the way you solve problems, so you can solve more problems! Woohoo! You can Code Like Coltrane, as Rich Hickey says. For better or for worse. Here's an unfortunate side effect I've noticed: my programs are vastly more complex and efficient than when I graduated from SICP a year ago, which is good, and yet I can't remember the last time I wrote code that was truly beautiful. Code I felt proud to call my code. Whose inner workings I could explain to a child. To me, efficient Python programs conceal so much of how they work, that striving for craftsmanship can feel alienating. It conceals so much. It's like a black box magic trick: in goes the value... (pause) oh, and there's the answer! And the obvious what's happening in between those two points, the less efficient my solution tends to be. The prize winning solutions are often the most opaque, the most dense with imported methods. And my programs look inevitably kind of haphazard and provisional. Like doodles. My Scheme programs, on the other hand, looked like Swiss clocks. They pleased me. They wouldn't have worked any other way. They molded to the precise, regimented form they had to be. I understood them. They were good. I like functional programming. I think the wall I'm hitting might be Python. The thought of a little Clojure or Haskell in my life right now sounds like a beach vacation.
- taeric 11y ago
  Swiss clocks feel impressive, no doubt. Quartz clocks, though, have the advantage of being accurate.
  - 59nadir 11y ago
    This has absolutely no relevance to the analogy.
    - taeric 11y ago
      If you are expecting working code to be as elegant as a "Swiss clock," you might want to reconsider what the goal actually is. Certainly there is something for coding in this way. Just as it can hold a certain delight to have an elegant looking watch. There is a good chance of overbuilding when I see this level of coding from colleagues. Myself included.
  - dagw 11y ago
    A lot of Swiss watches (even from the most high end brands) use quartz movements.
    - taeric 11y ago
      I felt it was safe to assume, for the analogy, that we were talking mechanical watches.
- a-saleh 11y ago
  > The thought of a little Clojure or Haskell in my life right now sounds like a beach vacation. This is the reason, why I started to do little side-projects with clojurescript and reagent [1] I love the way how programming with reagent is visual, with almost no friction. I just start repl, start browser, open the code, and every time I save file, I see how my program changes :-) Compared to my work, where it can take me the first hour to get into the zone, and additional 20 minutes each time I need to switch frameworks, it really feels like a vacation :) [1] https://reagent-project.github.io/index.html https://reagent-project.github.io/index.html
provemewrong 11y ago
The link to previos charpter in the blog post 404's (but I could navigate to it through the sidebar). Anyway, I'm looking forward to reading them when I get home and hope to see the following charpters as well.
- afronski 11y ago
  I've changed yesterday the structure and I've messed up previous links - it should be fine now. ;)
rjberry 11y ago
Clojure seems too high level for SICP. Scheme was a perfect fit because of how simple it is and how few language features or data structures it contained. You had to build everything yourself, which was kind of the point.
sbensu 11y ago
To the author: on the compound data structures example, it would be much better to return an anonymous function with `fn` than to use `defn`. `defn` is meant to add global definitions to the namespace, not to be used as a value.
- edem 11y ago
  This was confusing to me as well since in the Scheme examples they embed functions into each other with define. It may be useful to use letfn to achieve something similar.
  - brudgers 11y ago
    Implementing define in a way that allowed it to be used was one of Scheme's innovations relative to some of the other Lisps in the 1970's. It's idiomatic in part because it is easier for new programmers to read and Scheme historically and SICP perpetually are targeted at newer programmers. Clojure most definitely is not. It's not an accident that Clojure's fn is only two characters. It's design as a language encourages anonymous functions. Along with recur there are many fewer cases where the simpler ways to do something require a name. The fundamental problem of trying to port SICP to other languages is that SICP is not a book about programming in Scheme. It's a book about software engineering, and the points about software engineering are made in ways that can be readily illustrated in Scheme. Cons is used to illustrate engineering ideas, and while those ideas could be illustrated in Clojure, there's an impedance mismatch between cons and the roughly analogous constructs in Clojure. Part of the baby gets thrown out with the bathwater for little advantage...understanding Scheme probably makes someone a better Clojure programmer, while the force fit of SICP into Clojure probably won't.
ericmo 11y ago
There was another person doing SICP in Clojure too, but it's been frozen in chapter 2 for a couple of years now. https://github.com/ecmendenhall/sicpclojure https://github.com/ecmendenhall/sicpclojure Hope this one gets to cover the whole book.
- ericmo 11y ago
  Also really interesting: http://xuanji.appspot.com/isicp/ http://xuanji.appspot.com/isicp/
rachbowyer 11y ago
For those people in London (England) interested in SICP in Clojure, we are running a monthly study group. Our google groups group is https://groups.google.com/forum/#!forum/sicp-mailonline https://groups.google.com/forum/#!forum/sicp-mailonline and the code is at https://github.com/MailOnline/sicp-mailonline https://github.com/MailOnline/sicp-mailonline (each person has their own branch). We are just starting Chapter 3 and at the current rate of progress it will be at least a year before we have completed the entire book! Anyone interested is welcome to join us :-)
ninjakeyboard 11y ago
“I personally don't think SICP will help you much with Clojure. YMMV.” —Rich Hickey, author, Clojure programming language
- erikcw 11y ago
  My guess is that this is being taken out of context. I don't want to put words in Rick's mouth, but I imagine that he means that SICP won't help you learn Clojure the language. Not that SICP won't make you a better programmer in Clojure (and all other languages). Personally I found it helpful to work through the book in scheme (the language used in the book), porting some of the exercises to Clojure and other languages I'm interested in as a supplement.
markc 11y ago
There's also http://ecmendenhall.github.io/sicpclojure/pages/contents.html http://ecmendenhall.github.io/sicpclojure/pages/contents.htm... which is an actual translation of the book into Clojure, currently up to chapter 2.1.4. And the ill-fated sicpinclojure.com site, which looked beautiful and had such great promise, but mysteriously stalled and died. Looks like vqc below has done quite a few of the exercises. Nice. Tommy Hall's SICP Distilled seems like the best shot at a complete book now. It's running a bit behind schedule but appears to be in the home stretch. We'll see!
lrc 11y ago
I've spent a lot of time with SICP and with Clojure. The book changed my life, and I too considered working on "porting" the book, but there would be a considerable amount of friction. Clojure can do everything necesssary, but it's very unidiomatic to build data structures out of pairs in Clojure, and SICP spends a _lot_ of time implementing data structures with pairs. A reconsideration of SICP for the modern age would, I think, take vectors and maps and sets as given, and see what _additional_ magic could be built from there! Just start with sequences. Lazy sequences, which are so helpful in the expert system database that's built in SICP, are already right there in Clojure without the complications of force and delay. My thought is you could do a lot more with the higher level examples, but a lot of the first half of the book would have to be rethought. (The functional implementation of Conway's Life in O'Reilly's "Clojure Programming" is as good as anything in the first third of SICP, for example; the example of accelerating series convergence from SICP seems less exciting today than it used to, at least to me.)

132 points by MattF 11y ago

This is awesome! I would love to see this span the whole SICP book. There was a kickstarter campaign for something called SICP Distilled, a while back. However it requires your github login which seemed kind of sketchy and also none of the content works anyway - http://www.sicpdistilled.com/ http://www.sicpdistilled.com/. Maybe someone else knows more? Anyway I look forward to seeing more chapters on your blog.

vqc 11y ago

This is exciting; I've been looking forward to doing this exact thing myself. Some more solutions can be found at https://github.com/gregsexton/SICP-Clojure https://github.com/gregsexton/SICP-Clojure

neoncontrails 11y ago

I've been feeling the past few weeks the repeated impact of hitting a wall. Programming was starting to feel like grinding. I felt wistful for SICP, when programming was full of big ideas and elegant new approaches to problems my unprincipled brain's first instinct was to clobber by brute force -- and learned, quickly, in Scheme, it's hard to be artless. It is, I think, harder code gracelessly in Scheme than to code with grace: it has a way of bending your ideas to a form. I think that's my main complaint with Python. In Python, exactly the opposite is true: it doesn't force you to think overly hard about the way you solve problems, so you can solve more problems! Woohoo! You can Code Like Coltrane, as Rich Hickey says. For better or for worse. Here's an unfortunate side effect I've noticed: my programs are vastly more complex and efficient than when I graduated from SICP a year ago, which is good, and yet I can't remember the last time I wrote code that was truly beautiful. Code I felt proud to call my code. Whose inner workings I could explain to a child. To me, efficient Python programs conceal so much of how they work, that striving for craftsmanship can feel alienating. It conceals so much. It's like a black box magic trick: in goes the value... (pause) oh, and there's the answer! And the obvious what's happening in between those two points, the less efficient my solution tends to be. The prize winning solutions are often the most opaque, the most dense with imported methods. And my programs look inevitably kind of haphazard and provisional. Like doodles. My Scheme programs, on the other hand, looked like Swiss clocks. They pleased me. They wouldn't have worked any other way. They molded to the precise, regimented form they had to be. I understood them. They were good. I like functional programming. I think the wall I'm hitting might be Python. The thought of a little Clojure or Haskell in my life right now sounds like a beach vacation.

taeric 11y ago
Swiss clocks feel impressive, no doubt. Quartz clocks, though, have the advantage of being accurate.
- 59nadir 11y ago
  This has absolutely no relevance to the analogy.
  - taeric 11y ago
    If you are expecting working code to be as elegant as a "Swiss clock," you might want to reconsider what the goal actually is. Certainly there is something for coding in this way. Just as it can hold a certain delight to have an elegant looking watch. There is a good chance of overbuilding when I see this level of coding from colleagues. Myself included.
- dagw 11y ago
  A lot of Swiss watches (even from the most high end brands) use quartz movements.
  - taeric 11y ago
    I felt it was safe to assume, for the analogy, that we were talking mechanical watches.
a-saleh 11y ago
> The thought of a little Clojure or Haskell in my life right now sounds like a beach vacation. This is the reason, why I started to do little side-projects with clojurescript and reagent [1] I love the way how programming with reagent is visual, with almost no friction. I just start repl, start browser, open the code, and every time I save file, I see how my program changes :-) Compared to my work, where it can take me the first hour to get into the zone, and additional 20 minutes each time I need to switch frameworks, it really feels like a vacation :) [1] https://reagent-project.github.io/index.html https://reagent-project.github.io/index.html

provemewrong 11y ago

The link to previos charpter in the blog post 404's (but I could navigate to it through the sidebar). Anyway, I'm looking forward to reading them when I get home and hope to see the following charpters as well.

afronski 11y ago
I've changed yesterday the structure and I've messed up previous links - it should be fine now. ;)

rjberry 11y ago

Clojure seems too high level for SICP. Scheme was a perfect fit because of how simple it is and how few language features or data structures it contained. You had to build everything yourself, which was kind of the point.

sbensu 11y ago

To the author: on the compound data structures example, it would be much better to return an anonymous function with `fn` than to use `defn`. `defn` is meant to add global definitions to the namespace, not to be used as a value.

edem 11y ago
This was confusing to me as well since in the Scheme examples they embed functions into each other with define. It may be useful to use letfn to achieve something similar.
- brudgers 11y ago
  Implementing define in a way that allowed it to be used was one of Scheme's innovations relative to some of the other Lisps in the 1970's. It's idiomatic in part because it is easier for new programmers to read and Scheme historically and SICP perpetually are targeted at newer programmers. Clojure most definitely is not. It's not an accident that Clojure's fn is only two characters. It's design as a language encourages anonymous functions. Along with recur there are many fewer cases where the simpler ways to do something require a name. The fundamental problem of trying to port SICP to other languages is that SICP is not a book about programming in Scheme. It's a book about software engineering, and the points about software engineering are made in ways that can be readily illustrated in Scheme. Cons is used to illustrate engineering ideas, and while those ideas could be illustrated in Clojure, there's an impedance mismatch between cons and the roughly analogous constructs in Clojure. Part of the baby gets thrown out with the bathwater for little advantage...understanding Scheme probably makes someone a better Clojure programmer, while the force fit of SICP into Clojure probably won't.

ericmo 11y ago

There was another person doing SICP in Clojure too, but it's been frozen in chapter 2 for a couple of years now. https://github.com/ecmendenhall/sicpclojure https://github.com/ecmendenhall/sicpclojure Hope this one gets to cover the whole book.

ericmo 11y ago
Also really interesting: http://xuanji.appspot.com/isicp/ http://xuanji.appspot.com/isicp/

rachbowyer 11y ago

For those people in London (England) interested in SICP in Clojure, we are running a monthly study group. Our google groups group is https://groups.google.com/forum/#!forum/sicp-mailonline https://groups.google.com/forum/#!forum/sicp-mailonline and the code is at https://github.com/MailOnline/sicp-mailonline https://github.com/MailOnline/sicp-mailonline (each person has their own branch). We are just starting Chapter 3 and at the current rate of progress it will be at least a year before we have completed the entire book! Anyone interested is welcome to join us :-)

ninjakeyboard 11y ago

“I personally don't think SICP will help you much with Clojure. YMMV.” —Rich Hickey, author, Clojure programming language

erikcw 11y ago
My guess is that this is being taken out of context. I don't want to put words in Rick's mouth, but I imagine that he means that SICP won't help you learn Clojure the language. Not that SICP won't make you a better programmer in Clojure (and all other languages). Personally I found it helpful to work through the book in scheme (the language used in the book), porting some of the exercises to Clojure and other languages I'm interested in as a supplement.

markc 11y ago

There's also http://ecmendenhall.github.io/sicpclojure/pages/contents.html http://ecmendenhall.github.io/sicpclojure/pages/contents.htm... which is an actual translation of the book into Clojure, currently up to chapter 2.1.4. And the ill-fated sicpinclojure.com site, which looked beautiful and had such great promise, but mysteriously stalled and died. Looks like vqc below has done quite a few of the exercises. Nice. Tommy Hall's SICP Distilled seems like the best shot at a complete book now. It's running a bit behind schedule but appears to be in the home stretch. We'll see!

lrc 11y ago

I've spent a lot of time with SICP and with Clojure. The book changed my life, and I too considered working on "porting" the book, but there would be a considerable amount of friction. Clojure can do everything necesssary, but it's very unidiomatic to build data structures out of pairs in Clojure, and SICP spends a _lot_ of time implementing data structures with pairs. A reconsideration of SICP for the modern age would, I think, take vectors and maps and sets as given, and see what _additional_ magic could be built from there! Just start with sequences. Lazy sequences, which are so helpful in the expert system database that's built in SICP, are already right there in Clojure without the complications of force and delay. My thought is you could do a lot more with the higher level examples, but a lot of the first half of the book would have to be rethought. (The functional implementation of Conway's Life in O'Reilly's "Clojure Programming" is as good as anything in the first third of SICP, for example; the example of accelerating series convergence from SICP seems less exciting today than it used to, at least to me.)