Duncan Coutts wrote:
On Sun, 2008-11-09 at 19:18 +0000, Andrew Coppin wrote:
Generalised? Heck, I don't use list comprehension at all! :-P
Perhaps you should! :-)
When I first started with Haskell I kind of had the idea that list comprehensions were just for beginners and that 'real' hackers used just concatMaps and filters.
A couple years later I 'rediscovered' list comprehensions and I now use them frequently. There are many cases in real programs where simple and not-so-simple list comprehensions are the clearest way of expressing the solution. In particular the easy support for refutable pattern matching in the generators allows some succinct and clear code.
I don't actually use *lists* all that much - or at least not list transformations. And if I'm going to do something complicated, I'll usually write it as a do-expression rather than a comprehension.
Just a random example out of Cabal:
warn verbosity $ "This package indirectly depends on multiple versions of the same " ++ "package. This is highly likely to cause a compile failure.\n" ++ unlines [ "package " ++ display pkg ++ " requires " ++ display (PackageIdentifier name ver) | (name, uses) <- inconsistencies , (pkg, ver) <- uses ]
Pretty concise and clear I think.
Erm... yeah, it's not too bad once I change all the formatting to make it clear what's what. Wouldn't it be a lot easier as a do-block though?