在 2010年 1月 17日 星期日 11:02:59，michael rice 寫道: > I don't see anything wrong with this function, which just subtracts 1 from > the first element of an Int list (if there is a first element). > > Michael > > My function: > > dropFirst :: [Int] -> [Int] > dropFirst [] = [] > dropFirst (x:xs) = (x-1) : xs > > My output: > > :l dropfirst > > [1 of 1] Compiling Main ( dropfirst.hs, interpreted ) > Ok, modules loaded: Main. > *Main> dropFirst [3 4 5 6]
Use dropFirst [3,4,5,6], I think. > > <interactive>:1:11: > No instance for (Num (t -> t1 -> t2 -> Int)) > arising from the literal `3' at <interactive>:1:11-17 > Possible fix: > add an instance declaration for (Num (t -> t1 -> t2 -> Int)) > In the expression: 3 4 5 6 > In the first argument of `dropFirst', namely `[3 4 5 6]' > In the expression: dropFirst [3 4 5 6] > *Main> > _______________________________________________ Haskell-Cafe mailing list [email protected] http://www.haskell.org/mailman/listinfo/haskell-cafe
