> On Apr 18, 2019, at 12:08 PM, Luis Sanjuán <luisj.sanj...@gmail.com> wrote:
>
> The last month or so we all read some interesting posts about the convenience
> of examples or docs to facilitate the transition from other languages to
> Racket (from Python to Racket, from R to Racket, ...). Then I thought about
> another non-Racket languages that no one mention, if I recall well, for which
> such examples would be more than helpful, *SL languages ;)
>
> Of course, The Realm is there, but more examples would be beneficial, I
> guess. I have written something along these lines on my blog:
>
> https://los-pajaros-de-hogano.blogspot.com/2019/04/from-htdp-to-racket-isbn-extraction-in.html
>
> It might be full of inaccuracies or even errors. So comments, fixes, or
> suggestions are welcomed.
Luis, this is great. Thank you for the effort.
Here are some suggestions on how I’d re-order some of the material:
0. Importing all of racketbase and racket/string and racket/file first is
questionable. I would create a teachpack
htdp2racket
that includes the functions that are needed for writing such excerpts of
realistic programs. I’d be happy to collaborate on this and include the
teachpack with 2htdp.
1. I’d switch to #lang htdp/isl+ first. Your code should pose no problems for
this #lang. (It isn’t production ready yet).
2. Still in ISL+, I would add the 2htdp/abstraction teachpack to simplify the
ISLcode first. I think its suport of for and match fits.
3. A re-factoring of code must have the support of a test suite. There are
three ways to go about this:
(a) import rackunit into ISL+
(b) import racket-tests/test-engine into the racket/base program and
run (test) at the bottom
(c) rewrite the tests into rackunit + submdoule.
I’d go with (b) and do an optional last step to show people how to write
idiomatic rackunit tests.
4. I would not use define/contract for this transition sequence. See elsewhere
for its somewhat complex semantics when it comes to blame assignment. Instead
when you use contracts, it might be a good time to split the module into two
parts:
— the main functions
— the helpers and the large number of constant definitions plus
contracts (yes export the contracts from here if you can keep things opaque)
You could first show how to move code into a submodule with its own
contract-out plus a single require, then move the submodule into a file.
(That’s how I proceed and it should be a DrRacket refactoring operation.)
5. Years ago, I observed a PhD in our lab using point-free style in Racket. He
came from Haskell of course. I tried it. I got close to saying negative things
about it in the style guide.
I am a bit disappointed that the code didn't shrink during the transformation
but I didn’t spot immediate big gains, even with some small style guide things
fixed.
Again, thank you very much and please keep posting — Matthias
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