parsers/Parsers/Brainfuck/SymanticParser/Grammar.hs

   1 {-# LANGUAGE AllowAmbiguousTypes #-}
   2 {-# LANGUAGE ScopedTypeVariables #-}
   3 {-# LANGUAGE TemplateHaskell #-}
   4 {-# LANGUAGE TypeApplications #-}
   5 {-# LANGUAGE ViewPatterns #-}
   6 module Parsers.Brainfuck.SymanticParser.Grammar where
   7
   8 import Data.Char (Char)
   9 import Data.Function ((.))
  10 import qualified Prelude
  11
  12 import qualified Symantic.Parser as SP
  13
  14 import Parsers.Utils
  15 import Parsers.Brainfuck.Types
  16
  17 -- | Use with @$$(runParser @Text grammar)@,
  18 -- but in another Haskell module to avoid
  19 -- GHC stage restriction on such top-level splice.
  20 grammar :: forall tok repr.
  21   CoerceEnum Char tok =>
  22   CoerceEnum tok Char =>
  23   SP.Grammarable tok repr =>
  24   repr [Instruction]
  25 grammar = whitespace SP.*> bf
  26   where
  27   whitespace = SP.skipMany (SP.noneOf (coerceEnum @_ @tok Prelude.<$> "<>+-,.[]"))
  28   lexeme :: repr a -> repr a
  29   lexeme p = p SP.<* whitespace
  30   bf :: repr [Instruction]
  31   bf = SP.many (lexeme (SP.match (SP.look (SP.item @tok))
  32                                  (SP.prod . coerceEnum Prelude.<$> "<>+-,.[")
  33                                  op SP.empty))
  34   op :: SP.Production tok -> repr Instruction
  35   op prod = case coerceEnum (SP.runValue prod) of
  36     '<' -> SP.item @tok SP.$> SP.prod Backward
  37     '>' -> SP.item @tok SP.$> SP.prod Forward
  38     '+' -> SP.item @tok SP.$> SP.prod Increment
  39     '-' -> SP.item @tok SP.$> SP.prod Decrement
  40     ',' -> SP.item @tok SP.$> SP.prod Input
  41     '.' -> SP.item @tok SP.$> SP.prod Output
  42     '[' -> SP.between (lexeme (SP.item @tok))
  43                       (SP.token (coerceEnum @_ @tok ']'))
  44                       ($(SP.prodCon 'Loop) SP.<$> bf)
  45     _ -> Prelude.undefined