2010/8/26 michael rice
From: http://en.wikibooks.org/wiki/Haskell/Applicative_Functors
============================= import Control.Applicative
f :: (a -> b -> c) fmap :: Functor f => (d -> e) -> f d -> f e fmap f :: Functor f => f a -> f (b -> c) -- Identify d with a, and e with (b -> c)
sumsqr :: Int -> Int -> Int -- my f sumsqr i j = i*i+j*j =============================
I'm trying to understand how the above works but...
[michael@localhost ~]$ ghci GHCi, version 6.12.1: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. Loading package ffi-1.0 ... linking ... done. Prelude> :l bozo.hs [1 of 1] Compiling Main ( bozo.hs, interpreted )
bozo.hs:5:0: Invalid type signature Failed, modules loaded: none. Prelude>
Hi, The fifth line has the form x y :: ... instead of x :: ... This is not a legal type signature. Furthermore, you can't give fmap two signatures in the same source file. The reason this is given on the page you linked is for demonstration purpose (well, I guess, I haven't read it). Cheers, Thu