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data Number = singular | plural
data Person = 1st | 2nd | 3rd
data Gender = nonbinary | feminine | masculine | neutral

rule start = english_sentence + "."

rule english_sentence
  = pronoun.Number.Person.Gender are.Number.Person.Gender adj
  | subj.N1.G1 verb.N1.G1 obj.N2.G2 
  

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:- module(cfg_macro, [
    op(1200, xfx, ++>)
]).

:- op(1200, xfx, ++>).

/*
The rule:
s ++> np(blah), vp.
translates to:

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{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE PatternSynonyms #-}

import Debug.Trace ( trace )

type Ident = String

data Value
  = Var Ident
  | Bool Bool

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{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE BlockArguments #-}
{-# LANGUAGE PatternSynonyms #-}

import Data.Maybe
import Control.Monad.State
import Data.List

data Ty
  = Unit -- The unit type.

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:- op(600, yfx, '@').  % Function application
:- op(450, xfy, '=>'). % Type variable quantification
:- op(1150, fx, mode).

% Defines/validates a typing context.
tcx([]).
tcx([X-Sigma | Tcx]) :-
    atom(X),
    sigma_type(Sigma),
    tcx(Tcx).

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:- op(350, yfx, @).

:- set_prolog_flag(occurs_check, error).

:- det(inference/3).

inference(true, bool, _).

inference(false, bool, _).