On Sat, 12 Dec 2015 01:56:48 +0100, Dimitri DeFigueiredo
Couldn't match expected type ‘r’ with actual type ‘COParseResult’ ‘r’ is a rigid type variable bound by the type signature for getParseResult :: ParseResult r => String -> IO r ...
I have a PhD in computer science, but never really liked programming languages back then and somehow I never learned what a "rigid type variable" is.
See [Haskell-cafe] What is a rigid type variable? https://mail.haskell.org/pipermail/haskell-cafe/2008-June/044622.html :
But would anyone care to explain to a novice in a couple paragraphs why foldl (+) 0 [1..10^9] may take 10 Gigs of RAM to calculate?
The foldl builds up a very long expression and evaluates it after the last element of the list is reached (the evaluation is non-strict, or lazy). If you use foldl' (from Data.List) instead, the calculation is done per element (the evaluation is strict). For more details, see Foldr Foldl Foldl' https://wiki.haskell.org/Foldr_Foldl_Foldl' Lazy vs. non-strict https://wiki.haskell.org/Lazy_vs._non-strict Regards, Henk-Jan van Tuyl -- Folding@home What if you could share your unused computer power to help find a cure? In just 5 minutes you can join the world's biggest networked computer and get us closer sooner. Watch the video. http://folding.stanford.edu/ http://Van.Tuyl.eu/ http://members.chello.nl/hjgtuyl/tourdemonad.html Haskell programming --