How to get the declaration from a Z3 smtlib2 formula?

Question

I would like to do incremental solving with Z3 with the C++ API.

There are already some old questions, 2012, about this:

Z3 4.0 Z3_parse_smtlib2_string

Z3 4.0: get complete model

Z3 4.3.1 C-API parse_smtlib2_string: Where to get declarations from?

I would like to know if there is a solution with the new Z3 versions, 4.4.2.

Basically what I want to do it is something like this:

char *decl = "(declare-const p0 Bool)";
char *assert = "(assert(= p0 true))";

Z3_ast ast = Z3_parse_smtlib2_string(ctx, (Z3_string)decl, 0, 0, 0, 0, 0, 0);
z3::expr eq1(ctx, ast);
solver.add(eq1);

//extract declarations from the solver, ctx or ast
...

//Parse the assert with the previous declarations
Z3_ast ast = Z3_parse_smtlib2_string(ctx, (Z3_string)assert, 0, 0, 0, num_decls, symbols, decl_list);
z3::expr eq2(ctx, ast);
solver.add(eq2);
solver.check();

But I don't know how to get the declarations. I tried to use Z3_get_smtlib_num_decls, but it is only working with smtlib1, not with smtlib2.

Is there a way to retrieve the declarations? Will the function Z3_get_smtlib2_num_decls be implemented in the future?

Thank you for your time.

Answer 1

Like Nikolaj said in Z3 4.3.1 C-API parse_smtlib2_string: Where to get declarations from? , you'll have to traverse the expressions (assertions) to collect the declarations. The link to the tptp example is broken, but the file comes with Z3 as examples/tptp/tptp5.cpp (see the collect_decls function).

See also: Display declarations parsed from an SMT-LIB2 file