"""Satisfiability and Propositional Logic
Consider the following constraints:
– Alice can only meet either on Monday, Wednesday or Thursday
– Bob cannot meet on Wednesday
– Carol cannot meet on Friday
– Dave cannot meet neither on Tuesday nor on Thursday
– Question: When can the meeting take place?
- Encode then into the following Boolean formula:
(Mon ∨ Wed ∨ Thu) ∧ (¬Wed) ∧ (¬Fri) ∧ (¬Tue ∧ ¬Thu)
The meeting must take place on Monday
"""
import logging
from patternmatching import *
logging.basicConfig(format='%(message)s', level=logging.DEBUG)
options = [
'monday', 'wednesday', 'thursday', 'X',
'monday', 'tuesday', 'thursday', 'friday', 'X',
'monday', 'tuesday', 'wednesday', 'thursday', 'X',
'monday', 'wednesday', 'friday', 'X',
True,
]
constraints = (
padding + anyone * group('alice') + padding + 'X'
+ padding + anyone * group('bob') + padding + 'X'
+ padding + anyone * group('carol') + padding + 'X'
+ padding + anyone * group('dave') + padding + 'X'
+ like(lambda _: bound.alice == bound.bob == bound.carol == bound.dave)
)
assert match(options, constraints) # <-- FAILS! and I don't know why :(