grammatical-parsers-0.7: examples/Utilities.hs

{-# LANGUAGE FlexibleContexts, FlexibleInstances, KindSignatures, RankNTypes, ScopedTypeVariables #-}
module Utilities where

import Data.Functor.Compose (Compose(..))
import Data.Monoid ((<>))
import Data.Monoid.Textual (TextualMonoid, toString)

import Text.Grampa
import Text.Grampa.ContextFree.Memoizing.LeftRecursive
import qualified Rank2

parseUnique :: (Ord s, TextualMonoid s, Rank2.Traversable g, Rank2.Distributive g, Rank2.Apply g) =>
               Grammar g Parser s -> (forall f. g f -> f r) -> s -> r
parseUnique g prod s =
   case getCompose (prod $ parseComplete g s)
   of Left failure -> error ("Parse failure: " ++ toString (error "non-character") (failureDescription s failure 3))
      Right [x] -> x

infixJoin :: String -> String -> String -> String
infixJoin op a b = "(" <> a <> op <> b <> ")"