-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 ajb@spamcop.net wrote:
I updated the diff example a bit:
http://andrew.bromage.org/darcs/diff/
It now features TWO newtype synonyms. This illustrates a crucial feature of Haskell: Abstractions are cheap.
Okay, looking at that code: The comments before the type definitions are mostly good... now it looks like I'm going into critique mode :) Range (that is, the comment describing it) needs to say whether it's inclusive of its first and/or its last endpoint (in fact it is inclusive, I can determine by looking at the definition of rangeDist) I suppose Match is the same (inclusive), but I can't tell. And personally I don't know what the significance/meaning of a "found match" is. Comparing "data Range = Range Line Line" and "type Match = (Line,Line)", they are isomorphic, but declared differently (which is fine IMO) With just a little modification, it could use haddock syntax for the comments! I got a little lost reading the code. I think all the data/type definitions should be moved together, to the top. And the comments on the types enhanced a little to make it clearer how the algorithm goes. Or if diff is a weird confusing algorithm even in Haskell, put a more thorough description of why/how it uses those types and/or a reference to a paper on the subject, I would personally like :). Maybe that doesn't show off how clear Haskell itself is, or maybe it gives the reader a better chance of understanding it at all and thereby seeing how straightforward it is. I don't know, are there QuickCheck-style properties we can say about diff? (they are another valuable tool for understanding in detail what the code is supposed to do) The only IO that displayDiff does is putStrLn. It should probably return a string instead (and be called showDiff? would it be necessary to replace the putStrLn IO with some sort of writer monad to keep the code's clarity? or the ShowS-style sequencing/concatenation is (.) and output is (str++) (or, showLn: (\s -> str ++ '\n' : s)) -- that can be abstracted so it's not so ugly...) Then, displayDiff = putStr . showDiff Isaac -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFGJ09qHgcxvIWYTTURAhqrAJ9SFYmIifl5Ahf0umg0SnImGKr3tgCgwLze bZdTYUzmy+C2uXwFOkJOcdU= =KfVH -----END PGP SIGNATURE-----