On Wed, 2007-10-03 at 22:31 +1000, Stuart Cook wrote: > On 10/3/07, PR Stanley <[EMAIL PROTECTED]> wrote: > > Without looking at the standard prelude, define the > > higher-order library function curry that converts a function > > on pairs into a curried > > function, and conversely, the function uncurry > > that converts a curried > > function with two arguments into a function on pairs. > > In other words, take a function like[1] > > add a b = a + b > > and make the following possible: > > (uncurry add) (2, 3) > > Conversely, take a function like > > sub' (a, b) = a - b > > and make the following possible: > > (curry sub') 4 1 > > > > Hint: first write down the types of the two functions. > > This, I think, is the key part, and it's a useful technique for > Haskell in general. > > First, write down the (general) type of a curried function, and the > type of the corresponding uncurried function. Use those types to > figure out what types curry and uncurry should have. Once you've done > that, the implementation (which is pretty straightforward) should > reveal itself.
Indeed, modulo bottom, the implementation of these functions is -completely- determined by the types. Djinn, for example, can automatically generate the implementations from the types. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
