On Thu, Apr 14, 2011 at 12:29 PM, Sean Perry
I like your approach Felipe. Thanks. Definitely not something that would have been obvious from reading the library docs. I knew there was a better way hiding somewhere though. Had I been coding in Python or some other language I typically use I would have let Handle be the point of abstraction. Anything that looked like a File would work for me.
The Yesod Book contains a chapter about the enumerator package [1], although it isn't finished, yet. [1] http://www.yesodweb.com/book/enumerator
The definition of 'go' looks nice and elegant. What does 'the $!i here in 'go $! i+1' do?
As you know, f $ x is just f x. The $! operator, however, evaluates the second argument to weak head normal form (WHNF) before calling the function. In other words, f $! x = x `seq` f x If we just called "go (i+1)", a huge thunk would be created. For example, if the string was found in sector 1024, then it would return Just (((((···(1+1)···+1)+1)+1)+1)+1) instead of simply Just 1024. But, when we call "go $! i+1", we force the sum to be done *now*, so the funtion would return Just (1023+1) which doesn't cause any problems =). Cheers, -- Felipe.