#Try out pycosat with something really simple.
#pycosat is just a Python interface to the PicoSAT
#SAT solver.

#Our problem.  For lunch you have to order soup or salad, but not both.
#You only eat soup on cold days.  What should you order?
#p--you order soup
#q--you order salad
#r--it's cold.
#The conditions are (p XOR q) and (q-->r)
#We tranlate to CNF as
# (p or q) and (not p or not q) and (not q or r)
#Numbering variables 1,2,3 gives clauses
#1 2
#-1 -2
#-2 3

import pycosat

#return the first solution found

def soup_or_salad():
    formula=[[1,2],[-1,-2],[-2,3]]
    return pycosat.solve(formula)

#return every solution

def soup_or_salad2():
    formula=[[1,2],[-1,-2],[-2,3]]
    u=list(pycosat.itersolve(formula))
    return u

#What if there's no solution?
def soup_or_salad3():
    formula=[[1,2],[-1,-2],[-2,3],[1],[2]]
    return pycosat.solve(formula)