将Z3模型值导入C ++

Question

I'm writing some code to generate constraints for Z3 and then solve for results. I can print out the result by the command Z3_model_to_string(ctx,m) and the result shows x1-> 1 x2->100 where x1 and x2 are both int. My question is how I can save these integer values into C++ variables for future analysis?

Here is the part of code I wrote for Z3

Z3_model m;
context ctx;
Z3_ast fs;
string str = "(declare-const x1 Int) (assert (> x1 0)) (declare-const x2 Int) (assert (not (< x2 100)))" //Generated by some other function
fs  = Z3_parse_smtlib2_string(Z3_context(ctx), str, 0, 0, 0, 0, 0, 0);
Z3_assert_cnstr(Z3_context(ctx), fs);
Z3_lbool result = Z3_check_and_get_model(Z3_context(ctx), &m);
switch (result) {
case Z3_L_FALSE:
    printf("unsat\n");
    break;
case Z3_L_UNDEF:
    printf("unknown\n");
    printf("potential model:\n%s\n", Z3_model_to_string(Z3_context(ctx), m));
    break;
case Z3_L_TRUE:
    printf("sat\n%s\n", Z3_model_to_string(Z3_context(ctx), m));
    break;
}
int num_constants = Z3_get_model_num_constants(Z3_context(ctx), m);
model aaa(ctx,m);
for (i = 0; i< num_constants; i++) {
    z3::expr r = aaa.get_const_interp(aaa.get_func_decl(i));
}

Answer 1

Once you have a model m , you can use the get_const_intrp and get_func_interp functions in class model to obtain their values. For the case of simple integer variables there should be n constants (ie, constant functions) in the model, ie, m.num_consts() = n and

expr r = m.get_const_interp(m.get_const_decl(i));

will return the interpretation of the i -th constant in the model. For the case of simple integer constraints, the result will usually be an expr describing a numeric value, ie, r.is_numeral() should be true. We can get different representations of those model values through these functions:

for integers and other types:

Z3_get_numeral_string
Z3_get_numeral_decimal_string
Z3_get_numeral_int
Z3_get_numeral_uint
Z3_get_numeral_uint64
Z3_get_numeral_int64

for real/rational numbers:

Z3_get_numeral_small
Z3_get_numerator
Z3_get_denominator
Z3_get_numeral_rational_int64

where the last part of the name indicates what type of object will be returned. Note that these functions will return false if the model values don't fit into the return type (eg, number too large for the int range). If all model values are expected to be small, we can of course use these functions. The safe (and slow) way is to ask for a string and then convert it whatever big-integer representation you use for your application.

Note: The C++ API is only a thin layer on top of the C API and those two APIs are meant to be used together. Many functions only exist on the C layer and C++ objects like asts and exprs should convert automatically into the right kind of pointers for the C API.

Here is a complete example for this particular case. I took the liberty of rewriting some of the code in a more C++ like style:

#include <string>
using namespace std;

#include <z3++.h>
using namespace z3;

void main() {
    try {        
        context ctx;        
        Z3_string str = "(declare-const x1 Int) (assert (> x1 0)) (declare-const x2 Int) (assert (not (< x2 100)))"; //Generated by some other function
        expr fs(ctx, Z3_parse_smtlib2_string(Z3_context(ctx), str, 0, 0, 0, 0, 0, 0));

        solver s(ctx);
        s.add(fs);
        check_result cr = s.check();

        model aaa(ctx, s.get_model());
        int num_constants = aaa.num_consts();
        for (int i = 0; i < num_constants; i++) {
            func_decl fd = aaa.get_const_decl(i);
            z3::expr r = aaa.get_const_interp(fd);
        }
    }
    catch (z3::exception e) {
        std::cout << e.msg() << std::endl;
    }
}