如何循环 Z3 变量以在 python 中添加约束

Question

I want to loop a Z3 variable for adding constraints in python. Following code snippet might be helpful to clarify the problem I am facing.

from z3 import *

a = Int('a')
b = [Int( 'b_' + str(i)) for i in range(10)]

s = Solver()
s.add(a <= 4)

for i in range(a): ################## How to do this? #####################
    s.add(b[i] == 1)

s.check()
s.model()

Answer 1

You can't. That's the whole point of a symbolic variable. It's value can be anything (subject to constraints you put in, of course), and thus it cannot be passed as an argument to range .

Since your b 's come from a list, you should instead iterate over that range. Something like:

for i in range(10):
  s.add(Implies(i < a,  b[i] == 1))

Of course it depends on exactly what you are trying to achieve. Your question sounds like an instance of the XY problem . You might get a better answer if you ask about what you're trying to achieve, as opposed to how you can simulate range for a symbolic variable.