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module Builtins where
import qualified Data.Map as M
import Control.Monad.Except
import Types
builtinEnv :: Env
builtinEnv = M.fromList [
("+", builtinAdd2),
("-", builtinSubtract2),
("head", builtinHead),
("tail", builtinTail)
]
builtinAdd2 :: AST
builtinAdd2 =
let outer ast1 = do
(ASTInteger a) <- assertIsASTInteger ast1
let inner ast2 = do
(ASTInteger b) <- assertIsASTInteger ast2
return $ ASTInteger $ a + b
return $ ASTFunction $ inner
in ASTFunction outer
builtinSubtract2 :: AST
builtinSubtract2 =
let outer ast1 = do
(ASTInteger a) <- assertIsASTInteger ast1
let inner ast2 = do
(ASTInteger b) <- assertIsASTInteger ast2
return $ ASTInteger $ a - b
return $ ASTFunction $ inner
in ASTFunction outer
builtinHead :: AST
builtinHead =
let outer ast = do
(ASTVector vec) <- assertIsASTVector ast
when (length vec == 0) $ throwError $ LException $ "head of empty vector"
return $ head vec
in ASTFunction outer
builtinTail :: AST
builtinTail =
let outer ast = do
(ASTVector vec) <- assertIsASTVector ast
when (length vec == 0) $ throwError $ LException $ "tail of empty vector"
return $ ASTVector $ tail vec
in ASTFunction outer
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