这是我的代码:
type Niveles = (Int, Int, Int)
type Persona = (String, Niveles)
type Pocion = (String, [(String, Int, [Efectos])])
type Ingredientes = [(String, Int, [Efectos])]
type Efectos = Niveles -> Niveles
aplicar3 f (a,b,c) = (f a, f b, f c)
invertir3 (a,b,c) = (c,b,a)
fst3 (a,_,_) = a
snd3 (_,b,_) = b
trd3 (_,_,c) = c
personas = [("Harry",(11, 5, 4)), ("Ron",(6,4,6)), ("Hermione",(8,12,2)), ("Draco",(7,9,6))]
f1 (ns,nc,nf) = (ns+1,nc+2,nf+3)
f2 = aplicar3 (max 7)
f3 (ns,nc,nf)
| ns >= 8 = (ns,nc,nf+5)
| otherwise = (ns,nc,nf-3)
misPociones :: [Pocion]
misPociones = [
("Felix Felices",[("Escarabajos Machacados",52,[f1,f2]),("Ojo de Tigre Sucio",2,[f3])]),
("Multijugos",[("Cuerno de Bicornio en Polvo",10, [invertir3, (\(a,b,c) -> (a,a,c))]),("Sanguijuela hormonal",54,[(aplicar3 (*2)), (\(a,b,c) -> (a,a,c)) ])]),
("Flores de Bach",[("Orquidea Salvaje",8,[f3]), ("Rosita",1,[f1])])]
efectosDePocion pocion = map trd3 (elementos pocion)
elementos :: Pocion -> Ingredientes
elementos (_, ingredientes) = ingredientes
我在最后一段代码中遇到了问题,当我尝试使用函数“elementos”时:
elementos ("Felix Felices",[("Escarabajos Machacados",52,[f1,f2]),("Ojo de Tigre Sucio",2,[f3])])
我收到了一个错误信息:
<interactive>:311:1:
No instance for (Show ((Int, Int, Int) -> (Int, Int, Int)))
arising from a use of `print'
Possible fix:
add an instance declaration for
(Show ((Int, Int, Int) -> (Int, Int, Int)))
In a stmt of an interactive GHCi command: print it
有人可以向我解释一下吗?我该如何修复它?
newtype Func a b = Func(a-> b)
或类似方法,并为Show提供单独的实例。 - Lazersmoke