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module Parser where
import Ast
import Data.Maybe (isJust)
import Lexer
import Text.Parsec
import qualified Text.Parsec.Expr as E
import Text.Parsec.String (Parser)
binary s f assoc = E.Infix (reservedOp s >> return (BinOp f)) assoc
opTable =
[ [ binary "*" Mul E.AssocLeft,
binary "/" Div E.AssocLeft
],
[ binary "+" Plus E.AssocLeft,
binary "-" Minus E.AssocLeft
]
]
expr :: Parser Expr
expr = E.buildExpressionParser opTable factor
number :: Parser Expr
number = do
pos <- getPosition
n <- integer
return $ Num n pos
true :: Parser Expr
true = do
pos <- getPosition
reserved "true"
return $ Bool' True pos
false :: Parser Expr
false = do
pos <- getPosition
reserved "false"
return $ Bool' False pos
variable :: Parser Expr
variable = do
pos <- getPosition
var <- identifier
return $ Variable var pos
typ :: Parser Type
typ = do
p <- identifier
return $ Type p
typFn :: Parser Type
typFn = do
p <- parens $ commaSep typ
r <- optionMaybe $ do
reserved "->"
typ
return $ FuncType p r
type' :: Parser Type
type' = do
try typFn
<|> typ <?> "type"
arg :: Parser (String, Type, SourcePos)
arg = do
pos <- getPosition
i <- identifier
_ <- colonSep <?> "\":\" before type"
t <- type' <?> "type"
return $ (i, t, pos)
fdef :: Ident -> Bool -> Bool -> SourcePos -> Parser Expr
fdef ident priv anon pos = do
args <- parens $ commaSep arg
rtyp <-
optionMaybe
( do
_ <- colonSep <?> "\":\" before type"
rtyp <- type' <?> "return type"
return $ rtyp
)
body <- braces $ many statement
return $ Func ident args rtyp body priv anon pos
function :: Parser Expr
function = do
pos <- getPosition
priv <- optionMaybe $ reserved "private"
reserved "def"
ident <- identifier
fdef ident (isJust priv) False pos
lambdaId :: SourcePos -> Ident
lambdaId s =
"lambda" ++ "@" ++ show (sourceLine s) ++ "," ++ show (sourceColumn s)
lambda :: Parser Expr
lambda = do
pos <- getPosition
fdef (lambdaId pos) True True pos
return' :: Parser Expr
return' = do
pos <- getPosition
reserved "return"
value <- optionMaybe expr
reservedOp ";"
return $ Return value pos
call :: Parser Expr
call = do
pos <- getPosition
ident <- try lambda <|> variable
args <- parens $ commaSep expr
return $ Call ident args pos
var :: Parser Expr
var = do
pos <- getPosition
reserved "var"
(ident, typ, _) <- arg
reservedOp "=" <?> "assignation"
value <- expr
reservedOp ";"
return $ Var ident typ value pos
factor :: Parser Expr
factor =
number
<|> true
<|> false
<|> try call
<|> try lambda
<|> try variable
<|> parens expr
exprStmt :: Parser Expr
exprStmt = do
e <- expr <|> factor
reservedOp ";"
return $ e
statement :: Parser Expr
statement = do
try exprStmt
<|> return'
module' :: Parser Expr
module' = do
pos <- getPosition
reserved "module"
ident <- identifier
return $ Module ident pos
program :: Parser [Expr]
program = do
m <- module'
n <-
many $ do
function
<|> var
<|> statement <?> "statement"
return $ [m] ++ n
parse :: Parser [Expr]
parse = program
parseFromFile p fname = do
input <- readFile fname
return (runParser p () fname input)
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