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|
module Parser
( parseLine
, parseReplLine
) where
import Control.Monad ( ap )
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
sc :: Parser ()
sc = L.space space1 empty empty
lexeme :: Parser a -> Parser a
lexeme = L.lexeme sc
symbol :: String -> Parser String
symbol = L.symbol sc
-- def identifier disallows the import prefix dots
defIdentifier :: Parser String
defIdentifier = lexeme
((:) <$> (letterChar <|> char '_') <*> many (alphaNumChar <|> oneOf "?!'_-"))
-- TODO: write as extension to defIdentifier
identifier :: Parser String
identifier = lexeme
((:) <$> (letterChar <|> char '_') <*> many (alphaNumChar <|> oneOf "?!'_-."))
namespace :: Parser String
namespace =
lexeme ((:) <$> upperChar <*> many letterChar)
<|> string "."
<|> (space >> return "")
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 "["
exp <- parseExpression
symbol "]"
pure $ Abstraction exp
parseApplication :: Parser Expression
parseApplication = do
s <- sepBy1 parseSingleton space
pure $ foldl1 Application s
parseBruijn :: Parser Expression
parseBruijn = do
idx <- digitChar
space
pure $ Bruijn $ (read . pure) idx
parseNumeral :: Parser Expression
parseNumeral = do
num <- number
space
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
space
pure $ Variable var
parseSingleton :: Parser Expression
parseSingleton =
parseBruijn
<|> parseNumeral
<|> parseAbstraction
<|> parens parseApplication
<|> parseVariable
parseExpression :: Parser Expression
parseExpression = do
space
expr <- parseApplication <|> parseSingleton
space
pure expr
parseEvaluate :: Parser Instruction
parseEvaluate = Evaluate <$> parseExpression
parseDefine :: Parser Instruction
parseDefine = do
var <- defIdentifier
space
Define var <$> parseExpression
parseReplDefine :: Parser Instruction
parseReplDefine = do
var <- defIdentifier
space
symbol "="
space
Define var <$> parseExpression
parseComment :: Parser Instruction
parseComment = string "#" >> Comment <$> almostAnything
parseImport :: Parser Instruction
parseImport = do
string ":import "
space
path <- importPath
space
ns <- namespace
space
pure $ Import (path ++ ".bruijn") ns
parsePrint :: Parser Instruction
parsePrint = do
string ":print "
space
exp <- parseExpression
space
pure $ Evaluate exp
parseTest :: Parser Instruction
parseTest = do
string ":test "
exp1 <- parseExpression
space
symbol "="
space
exp2 <- parseExpression
pure $ Test exp1 exp2
parseLine :: Parser Instruction
parseLine =
try parseDefine
<|> try parseComment
<|> try parsePrint
<|> try parseImport
<|> try parseTest
parseReplLine :: Parser Instruction
parseReplLine =
try parseReplDefine
<|> try parseComment
<|> try parseEvaluate
<|> try parseImport
<|> try parseTest
|
