/
expressions.py
124 lines (99 loc) · 3.3 KB
/
expressions.py
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#!python3
"""
Output a massive list of mathematical expressions that produce
the desired output.
"""
import decimal
import sys
# Automatically take care of divisions by zero etc
decimal.setcontext(decimal.ExtendedContext)
class Expression(object):
__slots__= ['left', 'right']
def __init__(self, left, right):
self.left = left
self.right = right
class Number(Expression):
__slots__= ['value']
def __init__(self, value):
self.value = decimal.Decimal(value)
def evaluate(self):
return self.value
def __str__(self):
return str(self.value)
class Addition(Expression):
__slots__ = []
def evaluate(self):
return self.left.evaluate() + self.right.evaluate()
def __str__(self):
return "({0} + {1})".format(self.left, self.right)
class Subtraction(Expression):
__slots__= []
def evaluate(self):
return self.left.evaluate() - self.right.evaluate()
def __str__(self):
return "({0} - {1})".format(self.left, self.right)
class Multiplication(Expression):
__slots__= []
def evaluate(self):
return self.left.evaluate() * self.right.evaluate()
def __str__(self):
return "({0} * {1})".format(self.left, self.right)
class Division(Expression):
__slots__= []
def evaluate(self):
return self.left.evaluate() / self.right.evaluate()
def __str__(self):
return "({0} / {1})".format(self.left, self.right)
class Sqrt(Expression):
__slots__ = ['subexp']
def __init__(self, subexp):
self.subexp = subexp
def evaluate(self):
return self.subexp.evaluate().sqrt()
def __str__(self):
return "sqrt({0})".format(self.subexp)
def bruteforce(inputs, target, wiggle):
inputs = [Number(i) for i in inputs]
target = decimal.Decimal(target)
wiggle = decimal.Decimal(wiggle)
expressions = inputs
generated = inputs
checker = Checker(target, wiggle)
while True:
newgenerated = []
for g in generated:
for e in expressions:
tmp = [
Addition(g, e),
Subtraction(g, e),
Multiplication(g, e),
Division(g, e)
]
checker.check(tmp)
newgenerated.extend(tmp)
for e in expressions[0:len(expressions) - len(generated)]:
# Subtraction and division aren't commutative. This matters
# when the relation is not symmetric. However it is symmetric
# for the most recently generated elements, so we don't worry
# about commutivity for those.
tmp = [
Division(e, g),
Subtraction(e, g)
]
checker.check(tmp)
newgenerated.extend(tmp)
tmp = Sqrt(g)
checker.check([tmp])
newgenerated.append(tmp)
expressions.extend(newgenerated)
generated = newgenerated
class Checker(object):
def __init__(self, target, wiggle):
self.target = target
self.wiggle = wiggle
def check(self, lst):
for i in lst:
if abs(i.evaluate() - self.target) < self.wiggle:
print(i)
sys.stdout.flush()
bruteforce((10, 5, 7), 2.14, .005)