#!/usr/bin/env python
from __future__ import print_function
import nltk
from nltk.probability import DictionaryProbDist
from nltk.parse.generate import generate
from nltk.grammar import CFG
import random
import sys

sentences = []

grammar = CFG.fromstring("""
S    -> NP VP
VP   -> TV NP
VP   -> IV
VP   -> DatV NP NP
TV   -> 'saw'
IV   -> 'ate'
DatV -> 'gave'
NP   -> 'telescopes'
NP   -> 'Jack'

""")

for sentence in generate(grammar, n=100):
    sentences.append(' '.join(sentence))

print(random.choice(sentences))

grammar = grammar.FeatureGrammar.fromstring("""
% start DP
DP[AGR=?a] -> D[AGR=?a] N[AGR=?a]
N[AGR=[NUM='sg', GND='m']] -> 'boy'
D[AGR=[NUM='sg', PERS=3]] -> 'this' | 'that'
D[AGR=[NUM='pl', PERS=3]] -> 'these' | 'those'
D[AGR=[NUM='pl', PERS=1]] -> 'we'
D[AGR=[PERS=2]] -> 'you'
N[AGR=[NUM='pl', GND='m']] -> 'boys'
N[AGR=[NUM='sg', GND='f']] -> 'girl'
N[AGR=[NUM='pl', GND='f']] -> 'girls'
N[AGR=[NUM='sg']] -> 'student'
N[AGR=[NUM='pl']] -> 'students'
""")