On Tue, Mar 06, 2007 at 10:19:12PM +0000, David House wrote: > On 06/03/07, Nicolas Frisby <[EMAIL PROTECTED]> wrote: > >Composition with (.) builds a function, but you eventually want an > >Int, so we can't just use (.), but we can come pretty close. > > > >(sum . IntMap.elems . IntMap.IntersectionWith (\x y -> x*y) > >queryVector) rationalProjection > > Often written: > > f . g . h $ x
Alternativly, (f . g . h) x will work, too. > > This is often prefered to the alternative: > > f $ g $ h $ x > > As it's visually lighter, and involves less editing if you wanted to > get rid of the x (say, you were eta-reducing the expression). > > As to why: > > f . g . h . x > > doesn't work, (.) can only compose two functions, but x is not a > function, it is a value, so you have to apply it to the composite > function f . g . h using the ($) operator or parentheses. > > -- > -David House, [EMAIL PROTECTED] > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
