Purpose of z3::tactic and z3::goal -

i see can create goals, add them tactic, , create solver tactic.

what advantage of approach on creating z3::solver instance , adding expressions it?

tactics have different purpose. can create goal contains assertions/constraints , run tactic on goal, result of new set of (sub-)goals, i.e., new assertions/constraints. solvers determine satisfiability , won't produce new (sub-)goals.

tactics can converted solvers, such resulting solver run tactic, , if result conclusive (trivial sat/unsat), return result. if sub-goals produced tactic not conclusive, return "unknown".