module TimeFlies where

import CF

data Cat = S | NP | VP | PP | Adj | Det | Noun | Verb | Prep
	 deriving (Eq,Ord,Show)

type Tok = String

-- the time flies grammar, in Peter Ljunglöf normal form
timeFlies :: CF Cat Tok
timeFlies = mkCF S [
		    S    |> [NP,VP],
		    NP   |> [Adj,NP],
		    NP   |> [NP,PP],
		    NP   |> [Det,Noun],
		    NP   |> [Noun],
		    VP   |> [Verb,PP],
		    VP   |> [Verb,NP],
		    VP   |> [Verb],
		    PP   |> [Prep,NP]
		   ]
	           [
		    "time"  |: Noun,
		    "time"  |: Adj,
		    "time"  |: Verb,
		    "flies" |: Noun,
		    "flies" |: Verb,
		    "arrow" |: Noun,
		    "like"  |: Verb,
		    "like"  |: Prep,
		    "an"    |: Det
		   ]

-- the time flies grammar, but with np -> noun pp instead of np -> np pp
-- to avoid left recursion
timeFliesNoLR :: CF Cat Tok
timeFliesNoLR = 
    mkCF S [
	    S    |> [NP,VP],
	    NP   |> [Adj,NP],
	    NP   |> [Noun,PP],
	    NP   |> [Det,Noun],
	    NP   |> [Noun],
	    VP   |> [Verb,PP],
	    VP   |> [Verb,NP],
	    VP   |> [Verb],
	    PP   |> [Prep,NP]
	   ] [
	      "time"  |: Noun,
	      "time"  |: Adj,
	      "time"  |: Verb,
	      "flies" |: Noun,
	      "flies" |: Verb,
	      "arrow" |: Noun,
	      "like"  |: Verb,
	      "like"  |: Prep,
	      "an"    |: Det
	     ]

-- the time files grammar in chomsky normal form
timeFliesCNF :: CF Cat Tok
timeFliesCNF = mkCF S [
		       S    |> [NP,VP],
		       NP   |> [Adj,NP],
		       NP   |> [NP,PP],
		       NP   |> [Det,Noun],
		       VP   |> [Verb,PP],
		       VP   |> [Verb,NP],
		       PP   |> [Prep,NP]
		      ] [
			 "time"  |: Noun,
			 "time"  |: NP,
			 "time"  |: Adj,
			 "time"  |: Verb,
			 "time"  |: VP,
			 "flies" |: Noun,
			 "flies" |: NP,
			 "flies" |: Verb,
			 "flies" |: VP,
			 "arrow" |: Noun,
			 "arrow" |: NP,
			 "like"  |: Verb,
			 "like"  |: VP,
			 "like"  |: Prep,
			 "an"    |: Det
			]