- range and fixed restrictions on terms are based on constraints and can be violated temporarily.
- bv_eval currently does not allow updating over fixed bits which leads to non-termination. TODO
- lookahead only considers tabu when setting values of variables.
- avoid more platform specific behavior when using m_mk_extract,
- rename mk_eq in bool_rewriter to mk_eq_plain to distinguish it from mk_eq_rw
- rework bv_lookahead to be more closely based on sls_engine, which has much better heuristic behavior than attempt 1.
