39 lines
1.5 KiB
Haskell
39 lines
1.5 KiB
Haskell
{-# OPTIONS_HADDOCK ignore-exports #-}
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module Parser.PathParser where
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import Algorithms.QuadTree (Quad(NW, NE, SW, SE), Orient(North, South, West, East))
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import Control.Applicative
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import Data.Attoparsec.ByteString.Char8
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import qualified Data.ByteString.Char8 as B
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-- |Parse a string such as "ne, n, sw, e" into
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-- [Quad NE, Orient North, Quad SW, Orient East].
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stringToQuads :: String -> [Either Quad Orient]
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stringToQuads str = case parseOnly parsePath (B.pack str) of
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Left _ -> []
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Right xs -> xs
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where
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parsePath = many' ((parseQuad <|> parseOrient)
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<* many' (char ',')
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<* many' space)
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-- |Parses a string that represents a single quad.
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parseQuad :: Parser (Either Quad Orient)
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parseQuad =
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const (Left NW) <$> (string (B.pack "nw") <|> string (B.pack "NW"))
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<|> const (Left NE) <$> (string (B.pack "ne") <|> string (B.pack "NE"))
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<|> const (Left SW) <$> (string (B.pack "sw") <|> string (B.pack "SW"))
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<|> const (Left SE) <$> (string (B.pack "se") <|> string (B.pack "SE"))
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-- |Parses a string that represents a single Orientation.
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parseOrient :: Parser (Either Quad Orient)
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parseOrient =
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const (Right North) <$> (string (B.pack "n") <|> string (B.pack "N"))
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<|> const (Right South) <$> (string (B.pack "s") <|> string (B.pack "S"))
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<|> const (Right West) <$> (string (B.pack "w") <|> string (B.pack "W"))
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<|> const (Right East) <$> (string (B.pack "e") <|> string (B.pack "E"))
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