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|
module Parser
( parseBlock
, parseReplLine
) where
import Control.Monad ( ap
, void
)
import Data.Functor.Identity
import Data.Void
import Helper
import Text.Megaparsec hiding ( parseTest )
import Text.Megaparsec.Char
import qualified Text.Megaparsec.Char.Lexer as L
type Parser = Parsec Void String
-- exactly one space
-- TODO: replace many scs with sc
sc :: Parser ()
sc = void $ char ' '
-- zero or more spaces
scs :: Parser ()
scs = void $ takeWhileP (Just "white space") (== ' ')
lexeme :: Parser a -> Parser a
lexeme = L.lexeme scs
symbol :: String -> Parser String
symbol = L.symbol scs
-- def identifier disallows the import prefix dots
defIdentifier :: Parser String
defIdentifier =
lexeme
((:) <$> (letterChar <|> char '_') <*> many
(alphaNumChar <|> oneOf "?!'_-")
)
<?> "defining identifier"
-- TODO: write as extension to defIdentifier
identifier :: Parser String
identifier =
lexeme
((:) <$> (letterChar <|> char '_') <*> many
(alphaNumChar <|> oneOf "?!'_-.")
)
<?> "identifier"
namespace :: Parser String
namespace =
lexeme ((:) <$> upperChar <*> many letterChar)
<|> string "."
<|> (scs >> return "")
<?> "namespace"
parens :: Parser a -> Parser a
parens = between (symbol "(") (symbol ")")
almostAnything :: Parser String
almostAnything =
some $ oneOf ".`#~@$%^&*_+-=|;',/?[]<>(){} " <|> letterChar <|> digitChar
importPath :: Parser String
importPath = some $ oneOf "./_+-" <|> letterChar <|> digitChar
parseAbstraction :: Parser Expression
parseAbstraction = do
symbol "[" <?> "opening abstraction"
exp <- parseExpression
symbol "]" <?> "closing abstraction"
pure $ Abstraction exp
parseApplication :: Parser Expression
parseApplication = do
s <- sepBy1 parseSingleton scs
pure $ foldl1 Application s
parseBruijn :: Parser Expression
parseBruijn = do
idx <- digitChar
scs
pure $ Bruijn $ (read . pure) idx
parseNumeral :: Parser Expression
parseNumeral = do
num <- number <?> "signed number"
scs
pure $ decimalToTernary num
where
sign :: Parser (Integer -> Integer)
sign = (char '-' >> return negate) <|> (char '+' >> return id)
nat :: Parser Integer
nat = read <$> some digitChar
number :: Parser Integer
number = ap sign nat
parseVariable :: Parser Expression
parseVariable = do
var <- identifier
scs
pure $ Variable var
parseSingleton :: Parser Expression
parseSingleton =
parseBruijn
<|> parseNumeral
<|> parseAbstraction
<|> (parens parseApplication <?> "enclosed application")
<|> parseVariable
parseExpression :: Parser Expression
parseExpression = do
scs
expr <- parseApplication <|> parseSingleton
scs
pure expr <?> "expression"
parseEvaluate :: Parser Instruction
parseEvaluate = Evaluate <$> parseExpression
parseDefine :: Int -> Parser Instruction
parseDefine lvl = do
var <- defIdentifier
scs
exp <- parseExpression
-- TODO: Fix >1 sub-defs
subs <-
(try $ newline *> (sepEndBy (parseBlock (lvl + 1)) newline))
<|> (try eof >> return [])
pure $ Define var exp subs
parseReplDefine :: Parser Instruction
parseReplDefine = do
var <- defIdentifier
scs
symbol "="
scs
exp <- parseExpression
pure $ Define var exp []
parseComment :: Parser Instruction
parseComment = string "#" >> Comment <$> almostAnything <?> "comment"
parseImport :: Parser Instruction
parseImport = do
string ":import " <?> "import"
scs
path <- importPath
scs
ns <- namespace
scs
pure $ Import (path ++ ".bruijn") ns
parsePrint :: Parser Instruction
parsePrint = do
string ":print " <?> "print"
scs
exp <- parseExpression
scs
pure $ Evaluate exp
parseTest :: Parser Instruction
parseTest = do
string ":test " <?> "test"
exp1 <- parseExpression
scs
symbol "="
scs
exp2 <- parseExpression
pure $ Test exp1 exp2
-- TODO: Add comment/test [Instruction] parser and combine with (this) def block
parseBlock :: Int -> Parser Instruction
parseBlock lvl =
string (replicate lvl '\t')
*> try (parseDefine lvl)
<|> try parseComment
<|> try parsePrint
<|> try parseImport
<|> try parseTest
parseReplLine :: Parser Instruction
parseReplLine =
try parseReplDefine
<|> try parseComment
<|> try parseEvaluate
<|> try parseImport
<|> try parseTest
|
