On Sat, Sep 21, 2013 at 12:09 PM, Jingjing Duan <duanjingj...@gmail.com>wrote:
> Hi, > > I've been reading HTDP and I'm about half way through. To apply what I've > learned in the book to a bigger exercise, I decided to write a boggle > solver. > > You can find the code here: > https://github.com/jduan/boggle_scheme/blob/master/boggle.rkt > > Any feedback is greatly appreciated. I'm specifically looking for feedback > on: > > 1. Did I break the problem into right components? > 2. How can I make the code more idiomatic? > If you're halfway through HtDP, you should know the value of data definitions, contracts, and test cases. I don't see any of those in your program. That makes it very hard to tell what's going on in the code, and whether it's doing the right thing. Adding them after the fact should improve your code's readability. Adding them earlier -- during the design process of the code itself -- helps break things down into components in a natural way. > 3. Why is code so slow? It can take minutes to solve a 4 by 4 board. The > same board can be solved by a ruby program I wrote in much less time, like > a few seconds. I know recursive functions are a big reason but is there > anything? > "Recursive functions" have nothing to do with the kind of slowdown you're seeing. Your program is simply doing too much work. Start adding simple test cases for your functions and you may start to get a clearer idea of where a lot of the work is being done. The process of adding test cases may also suggest simpler ways to structure your program, both in terms of making it more idiomatic and in terms of doing less work. You might get a lot out of restarting this boggle exercise from the top down, starting with the function find-all-words and going through the design recipe step by step. You may be surprised how different the result is from what you've written, and how much more natural the solution you get is. In my own experience, it is also a much quicker process than taking something written as a whole without the design steps, and trying to add them in after the fact. However you proceed, please feel free to share your results and any other questions you have with the list. We love hearing about stuff like this! Thanks, > Jingjing > No problem. Glad to see you're interested in HtDP and Racket! Good luck! --Carl
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