Haskellは初めてです。「文字列」を含むコードのほぼすべての行で、この「スコープ外:データコンストラクター「文字列」」を取得しています
私のコードを見て、私が間違っていることを教えてください。本当にありがとうございました。
import Data.Maybe
data Op = Add | Sub | Mul | Div | And | Or | Not | Eq | Less | Great
deriving (Eq, Show)
data Exp = Literal Value
| Primitive Op [Exp]
| Variable String
| If Exp Exp Exp
| Let [(String, Exp)] Exp
deriving (Show, Eq)
data Value = Number Int
| Bool Bool
deriving (Eq, Show)
type Env = [(String, Value)]
eval :: Env -> Exp -> Value
eval e (Literal v) = v
eval e (Variable x) = fromJust (lookup x e)
--22
prim :: op -> [Value] -> Value
prim Add [Number a, Number b] = Number (a+b)
prim And [Bool a, Bool b] = Bool (a && b)
prim Sub [Number a, Number b] = Number (a-b)
prim Mul [Number a, Number b] = Number (a*b)
prim Div [Number a, Number b] = Number (a/b)
prim Or [Bool a, Bool b] = Bool (a || b)
prim Not [Bool a] = Bool (not a)
prim Eq [Number a, Number b] = Bool (a == b)
prim Eq [String a, String b] = Bool (a == b)
prim Less [Number a, Number b] = Bool (a < b)
prim Less [String a, String b] = Bool (a < b)
prim Great [Number a, Number b] = Bool (a > b)
prim Great [String a, String b] = Bool (a > b)