def gen_assignments(variables):
if not variables:
yield {}
else:
v, variables = variables[0], variables[1:]
for env in gen_assignments(variables):
yield assign(v, False, env)
yield assign(v, True, env)
def gen_assignments(variables):
if not variables:
yield {}
else:
v, variables = variables[0], variables[1:]
for env in gen_assignments(variables):
yield assign(v, False, env)
yield assign(v, True, env)
def solving(problem, env, variables):
"Try to extend a consistent assignment for problem to a satisfying one."
if not sat.seems_consistent(problem, env):
return None
if not variables:
return env
choice = choose_unit_literal(problem, env, variables)
if choice is not None:
v, value, variables = choice
return solving(problem, assign(v, value, env), variables)
v, variables = variables[0], variables[1:]
for value in (False, True):
result = solving(problem, assign(v, value, env), variables)
if result is not None:
return result
return None
def solving(problem, env, variables):
"Try to extend a consistent assignment for problem to a satisfying one."
if not sat.seems_consistent(problem, env):
return None
if not variables:
return env
choice = choose_unit_literal(problem, env, variables)
if choice is not None:
v, value, variables = choice
return solving(problem, assign(v, value, env), variables)
v, variables = variables[0], variables[1:]
for value in (False, True):
result = solving(problem, assign(v, value, env), variables)
if result is not None:
return result
return None
def solving(index, env, variables):
"Try to extend a consistent assignment for problem to a satisfying one."
if index is 'contradiction':
return None
if not variables:
return env
v, variables = variables[0], variables[1:]
for value in (False, True):
new_env = assign(v, value, env)
result = solving(on_update(index, new_env, v if value else -v),
new_env, variables)
if result is not None:
return result
return None
def assume(index, env, variables, unit_literals, v, value):
env = assign(v, value, env)
return solving(index, env, variables,
on_update(index, v if value else -v, env, unit_literals))
def assume(index, env, variables, unit_literals, v, value):
env = assign(v, value, env)
return solving(
index, env, variables,
on_update(index.get(v if value else -v, ()), env, unit_literals))
