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|
module Base (Expr (..)
, Env (..)
, LispNumber (..)
) where
import Data.IORef
data LispNumber = I Integer
| F Double
deriving (Eq, Ord)
instance Num LispNumber where
-- addition
(I a) + (I b) = I $ a + b
(F a) + (F b) = F $ a + b
(F a) + (I b) = F $ a + fromIntegral b
(I a) + (F b) = F b + I a
-- subtraction
(I a) - (I b) = I $ a - b
(F a) - (F b) = F $ a - b
(F a) - (I b) = F $ a - fromIntegral b
(I a) - (F b) = F b - I a
-- multiplication
(I a) * (I b) = I $ a * b
(F a) * (F b) = F $ a * b
(F a) * (I b) = F $ a * fromIntegral b
(I a) * (F b) = F b * I a
instance Fractional LispNumber where
(I a) / (I b) = F $ fromIntegral a / fromIntegral b
(F a) / (I b) = F $ a / fromIntegral b
(I a) / (F b) = recip $ F b / I a
(F a) / (F b) = F $ a / b
recip (F x) = F $ 1 / x
recip (I x) = F $ 1 / fromIntegral x
-- TODO: use LispNumber (src/Operators.hs) here instead of IntLiteral and FloatLiteral
-- TODO: add character literals: \#a \#b \#c \#space \#newline
-- TODO: add support for complex numbers, oct and hex numbers
data Expr = List [Expr]
| Vector [Expr]
| DottedList [Expr] Expr
| StringLiteral String
| Number LispNumber
| BoolLiteral Bool
| Id String
| Function { params :: [String]
, body :: Expr
, extendedEnv :: Env
}
deriving (Eq)
type Env = IORef [(String, IORef Expr)]
showLispList :: [Expr] -> String
showLispList = unwords . map show
instance Show Expr where
show (DottedList xs x) = "(" ++ showLispList xs ++ " . " ++ show x ++ ")"
show (List xs) = "(" ++ showLispList xs ++ ")"
show (Vector xs) = "#(" ++ showLispList xs ++ ")"
show (StringLiteral s) = "\"" ++ s ++ "\""
show (Number (I n)) = show n
show (Number (F n)) = show n
show (BoolLiteral True) = "#t"
show (BoolLiteral False) = "#f"
show (Id i) = i
|
