带字符串表达式的 Z3 [英] Z3 with string expressions

问题描述

我正在尝试使用 Z3 来确定表达式是否可满足.我可以通过定义上下文，然后定义 int_const 变量和公式来轻松地做到这一点.要以编程方式计算表达式，您必须在代码中编写所有内容.假设逻辑表达式以字符串的形式给出，然后呢?例如，

I'm trying to use Z3 to determine if an expression is satisfiable. I could easily do this by defining the context then the int_const variables and the formula. To evaluate an expression programmatically you would have to write everything in code. Let's say the logical expression is given in the form of a string, what then? For example,

"x == y && !x == z"

"x == y && !x == z"

将在 C API 中表示为:

would be expressed in the C API as:

context c;
expr x = c.int_const("x")
//Same for other variables
...
formula = (x == y) && (!x == z);
solver s(c);
s.add(formula);
//s.check() ...etc etc

好的，我可以为这个特定的公式编写代码，但是给定一个字符串，我怎么能以编程方式做到这一点.我愿意接受你能想到的任何事情.

Okay, I can write the code for this particular formula, but how could I do that programmatically given a string. I'm open to anything you can think of.

谢谢:)

推荐答案

我看到以下选项:

1) 您可以实现自己的解析器，并调用 Z3 API 函数.优点:您可以使用最喜欢的"语言来编写公式.缺点:这是忙碌"的工作.

1) you can implement your own parser, and invoke the Z3 API functions. Pro: you can use your "favorite" language for writing formulas. Con: it is "busy" work.

2) 您可以使用 API Z3_parse_smtlib2_string.缺点:您的公式必须采用 SMT 2.0 格式.例如，您必须编写 (and (= x y) (not (= x y))) 而不是 (x == y) &&!(x == z).

2) you can use the API Z3_parse_smtlib2_string. Con: your formulas must be in SMT 2.0 format. For example, you would have to write (and (= x y) (not (= x y))) instead of (x == y) && !(x == z).

3) 您可以使用 Z3 Python API，并使用 Python 中的 eval 函数解析字符串.下面是一个例子:

3) You can use the Z3 Python API, and parse strings using the eval function in Python. Here is an example:

from z3 import *
# Creating x, y 
x = Int('x')
y = Int('y')

# Creating the formula using Python
f = And(x == y, Not(x == y))
print f

# Using eval to parse the string.
s = "And(x == y, Not(x == y))"
f2 = eval(s)
print f2

顺便说一句，这个脚本在rise4fun http://rise4fun.com/z3py 上不起作用，因为函数eval 在那里是不允许的，但您可以在本地 Z3 安装中使用上面的脚本.

BTW, this script does not work at rise4fun http://rise4fun.com/z3py because the function eval is not allowed there, but you can use the script above in your local Z3 installation.

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