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|
module Parser
( parseBlock
, parseReplLine
) where
import Control.Monad ( ap
, void
)
import Data.Void
import Helper
import Text.Megaparsec hiding ( parseTest )
import Text.Megaparsec.Char
type Parser = Parsec Void String
-- exactly one space
sc :: Parser ()
sc = void $ char ' '
-- zero or more spaces
-- scs :: Parser ()
-- scs = void $ takeWhileP (Just "white space") (== ' ')
-- def identifier disallows the import prefix dots
defIdentifier :: Parser String
defIdentifier =
((:) <$> (letterChar <|> char '_') <*> many (alphaNumChar <|> oneOf "?!'_-"))
<?> "defining identifier"
-- TODO: write as extension to defIdentifier
identifier :: Parser String
identifier =
((:) <$> (letterChar <|> char '_') <*> many (alphaNumChar <|> oneOf "?!'_-."))
<?> "identifier"
namespace :: Parser String
namespace =
((:) <$> upperChar <*> many letterChar) <|> string "." <?> "namespace"
parens :: Parser a -> Parser a
parens = between (string "(") (string ")")
importPath :: Parser String
importPath = some $ oneOf "./_+-" <|> letterChar <|> digitChar
parseAbstraction :: Parser Expression
parseAbstraction = do
_ <- string "[" <?> "opening abstraction"
e <- parseExpression
_ <- string "]" <?> "closing abstraction"
pure $ Abstraction e
-- one or more singletons wrapped in coupled application
parseApplication :: Parser Expression
parseApplication = do
s <- sepEndBy1 parseSingleton sc -- TODO: Fix consuming space at end (re. test =)
pure $ foldl1 Application s
parseBruijn :: Parser Expression
parseBruijn = do
idx <- digitChar <?> "bruijn index"
pure $ Bruijn $ (read . pure) idx
parseNumeral :: Parser Expression
parseNumeral = do
num <- number <?> "signed number"
pure $ decimalToTernary num
where
sign :: Parser (Integer -> Integer)
sign = (char '-' >> return negate) <|> (char '+' >> return id)
nat :: Parser Integer
nat = read <$> some digitChar
number :: Parser Integer
number = ap sign nat
specialEscape :: Parser Char
specialEscape =
choice (zipWith (\c r -> r <$ char c) "bnfrt\\\"/" "\b\n\f\r\t\\\"/")
parseString :: Parser Expression
parseString = do
str <- between
(char '\"')
(char '\"')
(some $ (char '\\' *> specialEscape) <|> (satisfy (`notElem` "\"\\")))
pure (stringToExpression str) <?> "string"
parseChar :: Parser Expression
parseChar = do
ch <- between (char '\'') (char '\'') (satisfy (`notElem` "\"\\"))
pure (charToExpression ch) <?> "char"
parseVariable :: Parser Expression
parseVariable = do
var <- identifier
pure $ Variable var
parseSingleton :: Parser Expression
parseSingleton =
parseBruijn
<|> parseNumeral
<|> parseString
<|> parseChar
<|> parseAbstraction
<|> (parens parseApplication <?> "enclosed application")
<|> parseVariable
parseExpression :: Parser Expression
parseExpression = do
e <- parseApplication
pure e <?> "expression"
parseEvaluate :: Parser Instruction
parseEvaluate = do
inp <- getInput
e <- parseExpression
pure $ ContextualInstruction (Evaluate e) inp
parseDefine :: Int -> Parser Instruction
parseDefine lvl = do
inp <- getInput
var <- defIdentifier
sc
e <- parseExpression
-- TODO: Fix >1 sub-defs
subs <-
(try $ newline *> (many (parseBlock (lvl + 1)))) <|> (try eof >> return [])
pure $ ContextualInstruction (Define var e subs) inp
parseReplDefine :: Parser Instruction
parseReplDefine = do
inp <- getInput
var <- defIdentifier
_ <- string " = "
e <- parseExpression
pure $ ContextualInstruction (Define var e []) inp
parseComment :: Parser ()
parseComment = do
_ <- string "# " <?> "comment"
_ <- some $ noneOf "\r\n"
return ()
parseImport :: Parser Instruction
parseImport = do
inp <- getInput
_ <- string ":import " <?> "import"
path <- importPath
ns <- (try $ sc *> namespace) <|> (eof >> return "")
pure $ ContextualInstruction (Import (path ++ ".bruijn") ns) inp
parsePrint :: Parser Instruction
parsePrint = do
inp <- getInput
_ <- string ":print " <?> "print"
e <- parseExpression
pure $ ContextualInstruction (Evaluate e) inp
parseTest :: Parser Instruction
parseTest = do
inp <- getInput
_ <- string ":test " <?> "test"
e1 <- parseExpression
_ <- string "= " -- TODO: Disallow missing space (non-trivial)
e2 <- parseExpression
pure $ ContextualInstruction (Test e1 e2) inp
parseCommentBlock :: Parser Instruction
parseCommentBlock = do
inp <- getInput
_ <- sepEndBy1 parseComment newline
eof
return $ ContextualInstruction Comment inp
-- TODO: Add comment/test [Instruction] parser and combine with (this) def block?
parseDefBlock :: Int -> Parser Instruction
parseDefBlock lvl =
(sepEndBy parseComment newline)
*> string (replicate lvl '\t')
*> ( try (parseDefine lvl)
<|> try parsePrint
<|> try parseImport
<|> try parseTest
)
parseBlock :: Int -> Parser Instruction
parseBlock lvl = try parseCommentBlock <|> parseDefBlock lvl
parseReplLine :: Parser Instruction
parseReplLine =
try parseReplDefine
<|> try parseEvaluate
<|> try parseImport
<|> try parseTest
|
