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module Quox.Lexer
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import Quox.Error
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import Data.String
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import public Text.Lexer
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import public Text.Lexer.Tokenizer
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import Generics.Derive
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%default total
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%language ElabReflection
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public export
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record Error where
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constructor Err
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reason : StopReason
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line, col : Int
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char : Char
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public export
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data Punc
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= LParen | RParen
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| LSquare | RSquare
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| LBrace | RBrace
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| Comma
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| Colon | DblColon
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| Arrow | DblArrow
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| Times | Triangle
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| Wild
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%runElab derive "Punc" [Generic, Meta, Eq, Ord, DecEq, Show]
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public export
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data Token
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= P Punc
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| Name String | Symbol String
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%runElab derive "Token" [Generic, Meta, Eq, Ord, DecEq, Show]
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nameStart = pred $ \c => isAlpha c || c == '_'
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nameCont = pred $ \c => isAlphaNum c || c == '_' || c == '\''
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name = nameStart <+> many nameCont <+> reject nameCont
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wild = exact "_" <+> reject nameCont
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%hide Text.Lexer.symbol
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symbol = exact "'" <+> name
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skip : Lexer -> Tokenizer (Maybe a)
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skip lex = match lex $ const Nothing
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simple : List String -> a -> Tokenizer (Maybe a)
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simple str x = match (choice $ map exact str) $ const $ Just x
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choice : (xs : List (Tokenizer a)) -> {auto 0 _ : So (isCons xs)} -> Tokenizer a
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choice (t :: ts) = foldl (\a, b => a <|> b) t ts
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tokens : Tokenizer (Maybe Token)
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tokens = choice [
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skip $ lineComment $ exact "--",
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skip $ blockComment (exact "{-") (exact "-}"),
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skip spaces,
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simple ["("] $ P LParen, simple [")"] $ P RParen,
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simple ["["] $ P LSquare, simple ["]"] $ P RSquare,
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simple ["{"] $ P LBrace, simple ["}"] $ P RBrace,
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simple [","] $ P Comma,
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simple ["::", "∷"] $ P DblColon,
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simple [":"] $ P Colon,
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simple ["->", "→"] $ P Arrow,
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simple ["=>", "⇒"] $ P DblArrow,
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simple ["**", "×"] $ P Times,
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simple ["<<", "⊲"] $ P Triangle,
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match wild $ const $ Just $ P Wild,
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match name $ Just . Name,
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match symbol $ Just . Symbol . assert_total strTail
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]
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export
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lex : MonadThrow Error m => String -> m (List (WithBounds Token))
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lex str =
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let (res, (reason, line, col, str)) = lex tokens str in
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case reason of
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EndInput => pure $ mapMaybe sequence res
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_ => let char = assert_total strIndex str 0 in
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throw $ Err {reason, line, col, char}
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