A few days ago, for various reasons, I've started to look at Haskell. At first I was quite impressed, after reading some FAQ, and some tutorials. Evrything was nice and easy ... until I've started writing some code on my own. What I should have been told about upfront: - the syntax for an expression - the syntax for a block - the adhoc syntax rules (how to distinguish among a tuple and a pharanthesized expression and how to find the start and end of a block for example ) - the fact that lambda expressions are not the same thing as "algebraic data" values - what guarantees are made by the LANGUAGE that an IO action (such as do putStrLn "Hello world" ) is not performed twice - the lambda expressions can be written (input) but cannot be printed (output) The biggest problem for me, so far, is the last one. Here is some strange example: module Hugs where aa::Int aa=7 cc:: (Int->Int)->(Int->Int->Int)->Int->(Int->Int) cc a op b = \x-> case x of { _ | x==aa -> x+1 ; _-> a x `op` b } f::Int->Int f(1)=1 f(2)=2 f(_)=3 g::Int->Int g(1)=13 g(2)=23 g(_)=33 h::[Int->Int] -> Int ->Int h [] x = x h [rr] x = let { u=Hugs.f ; v=Hugs.g } in case rr of { u -> Hugs.g(x)+aa ; v -> Hugs.f(x)+aa ; _ ->rr (x) + aa } h (rr:ll) x = h [rr] x + h (ll) x What I don't understand is why I'm forced to use guards like x==aa in cc, when aa is clearly bounded (is 7) and why in function h, the bounded u and v become free variables in the case expression. ________ Information from NOD32 ________ This message was checked by NOD32 Antivirus System for Linux Mail Servers. part000.txt - is OK http://www.eset.com