3 commits

Author	SHA1	Message	Date
Nikolaj Bjorner	f48040d809	Add Phase 3: Nielsen transformation engine and equation solving ... - New nseq_nielsen.h/cpp in src/ast/rewriter/: self-contained Nielsen transformation engine for word equations - simplify(): strip common prefix/suffix, empty elimination, variable stripping, single-var assignment detection - split(): case analysis for var vs constant, var vs var - is_conflict(): mismatch detection (different constants, one side has constants while other is empty) - Wire Nielsen into theory_nseq: - solve_eqs()/solve_eq(): process word equations using Nielsen transformations with e-graph canonization - branch_eq()/branch_var_prefix(): binary empty/non-empty decisions and prefix enumeration (no fresh variable creation) - canonize(): rewrite equation sides using current e-graph equivalences - all_eqs_solved(): check if all equations are satisfied - mk_value(): basic model generation (walk e-class for string constants) - Passes basic tests: simple equalities, concat equations, unsat detection Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>	2026-02-27 18:01:08 -08:00
Nikolaj Bjorner	58b57b2632	Add Phase 2: core data structures for theory_nseq ... - nseq_constraint.h: constraint types (nseq_eq, nseq_ne, nseq_mem, nseq_pred) with dependency tracking via scoped_dependency_manager - nseq_state.h/cpp: backtrackable state management with scoped_vector collections, axiom queue, length tracking, linearization for conflict/propagation justifications, statistics, display - theory_nseq.h/cpp: full internalization (term/atom/bool), equality and disequality handling with union-find, literal assignment dispatch (prefix/suffix/contains/in_re), axiom management, propagation helpers (propagate_eq/lit, set_conflict), scope push/pop wired to nseq_state Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>	2026-02-27 17:26:10 -08:00
Nikolaj Bjorner	c325c56de4	Add theory_nseq skeleton: new string solver selectable via smt.string_solver=nseq ... Phase 1 of the theory_nseq implementation: a stub theory solver for strings based on Nielsen transformations and lazy regex membership. - New files: theory_nseq.h/cpp with all required theory virtual methods - Add 'nseq' to smt.string_solver parameter validation and documentation - Wire into smt_setup.cpp dispatch (setup_QF_S, setup_seq_str, setup_nseq) - Currently returns FC_GIVEUP for non-trivial string constraints Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>	2026-02-27 17:00:59 -08:00