On Sat, Jul 31, 2010 at 5:59 PM, michael rice <nowg...@yahoo.com> wrote: > > OK, in f, *length* already knows it's argument is a list. > > In g, *length* doesn't know what's inside the parens, extra evaluation there. > So g is already ahead before we get to what's inside the [] and ().
According to the types, we already know both are lists. The question is, of course, what kind of list. > But since both still have eval x to *thunk* : *thunk*, g evaluates "to a > deeper level?" > > Michael > I think this question is being quite sneaky. The use of head and tail is pretty much irrelevant. Try the pointfree versions: f = length . (:[]) . head g = length . tail and see if that helps you see why f is lazier than g. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
