Hi, Henning Thielemann wrote:
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The notation [f x | x <- xs] describes operations on list elements, and looks like the imperative "forall x in xs do f x", whereas map f xs is a list transformation. The second one is more abstract, isn't it?
for that simple example yes, but what's about list comprehensions like: sequence of parsers: (p <+> q) r = [ (f (x,y), r2) | (x, r1) <- p r, (y, r2) <- q r1 ] or triples: [ (x,y,z) | x<-[1..n], let x2=x*x, y<-[1..x], let y2=y*y, let z=isq (x2,y2), x2+y2==z*z ] or database queries: [ (name,salary) | ((_,name),dateofbirth,((Just salary))) <- table, dateofbirth>1980 && salary>100000 ] I just typed these examples but did not check them. There are many other examples like n queens, functions on shaped matrices etc. Cheers -- Christoph