Well, i have tried cons (:) operator but when it passed to foldr doesn't work because cons operator operates first character and then the list but the foldr argument takes a function (a->a->a). Maybe i am missing the point here?
Aaron Denney wrote: > > On 2007-08-14, Alexteslin <[EMAIL PROTECTED]> wrote: >> >> Hi, >> >> I am trying to do the exercise which asks to define built-in functions >> 'last' and 'init' using 'foldr' function, such as last "Greggery Peccary" >> = >> 'y' >> >> the type for my function is: >> >> myLast :: [Char] -> Char >> >> I am not generalizing type so that make it less complicated. But what >> ever >> i am trying would not work. The only function type foldr takes as an >> argument is either (a->a->a) or (a->b->b) and none of the functions i >> found >> that would match this type from Char to Char. So in other words should >> be >> (Char->Char-Char). I can define the function without foldr but that >> misses >> the point of the exercise. > > Folds replace the "cons" operator (:) with the function you pass it. > If you want the tail of the list, you want what is on the right hand > side of every cons (unless that's []). > > -- > Aaron Denney > -><- > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > > -- View this message in context: http://www.nabble.com/defining-last-using-foldr-tf4269357.html#a12151694 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
