/*++
Copyright (c) 2011 Microsoft Corporation

Module Name:

    seq_decl_plugin.h

Abstract:

    decl_plugin for the theory of sequences

Author:

    Nikolaj Bjorner (nbjorner) 2011-11-14

Revision History:

    Updated to string sequences 2015-12-5

    Add SMTLIB 2.6 support 2020-5-17

--*/
#ifndef SEQ_DECL_PLUGIN_H_
#define SEQ_DECL_PLUGIN_H_

#include "ast/ast.h"
#include "ast/bv_decl_plugin.h"

#define Z3_USE_UNICODE 0

enum seq_sort_kind {
    SEQ_SORT,
    RE_SORT,
#if Z3_USE_UNICODE
    _CHAR_SORT,     // internal only
#endif
    _STRING_SORT,  
    _REGLAN_SORT
};

enum seq_op_kind {
    OP_SEQ_UNIT,
    OP_SEQ_EMPTY,
    OP_SEQ_CONCAT,
    OP_SEQ_PREFIX,
    OP_SEQ_SUFFIX,
    OP_SEQ_CONTAINS,
    OP_SEQ_EXTRACT,
    OP_SEQ_REPLACE,
    OP_SEQ_AT,
    OP_SEQ_NTH,         // NTH function exposed over API. Rewritten to NTH(s,i) := if (0 <= i < len(s)) then NTH_I(s,i) else NTH_U(s,i)
    OP_SEQ_NTH_I,       // Interpreted variant of Nth for indices within defined domain.
    OP_SEQ_NTH_U,       // Uninterpreted variant of Nth for indices outside of uniquely defined domain.
    OP_SEQ_LENGTH,
    OP_SEQ_INDEX,
    OP_SEQ_LAST_INDEX,
    OP_SEQ_TO_RE,
    OP_SEQ_IN_RE,
    OP_SEQ_REPLACE_RE_ALL, // Seq -> RegEx -> Seq -> Seq
    OP_SEQ_REPLACE_RE,     // Seq -> RegEx -> Seq -> Seq
    OP_SEQ_REPLACE_ALL,    // Seq -> Seq -> Seq -> Seq

    OP_RE_PLUS,
    OP_RE_STAR,
    OP_RE_OPTION,
    OP_RE_RANGE,
    OP_RE_CONCAT,
    OP_RE_UNION,
    OP_RE_DIFF,
    OP_RE_INTERSECT,
    OP_RE_LOOP,
    OP_RE_POWER,
    OP_RE_COMPLEMENT,
    OP_RE_EMPTY_SET,
    OP_RE_FULL_SEQ_SET,
    OP_RE_FULL_CHAR_SET,
    OP_RE_OF_PRED,


    // string specific operators.
    OP_STRING_CONST,
    OP_STRING_ITOS,
    OP_STRING_STOI,
    OP_STRING_LT,
    OP_STRING_LE,
    OP_STRING_IS_DIGIT,
    OP_STRING_TO_CODE,
    OP_STRING_FROM_CODE,

#if Z3_USE_UNICODE
    OP_CHAR_CONST,    // constant character
    OP_CHAR_LE,       // Unicode comparison
#endif
    // internal only operators. Converted to SEQ variants.
    _OP_STRING_STRREPL,
    _OP_STRING_CONCAT,
    _OP_STRING_LENGTH,
    _OP_STRING_STRCTN,
    _OP_STRING_PREFIX,
    _OP_STRING_SUFFIX,
    _OP_STRING_IN_REGEXP,
    _OP_STRING_TO_REGEXP,
    _OP_STRING_CHARAT,
    _OP_STRING_SUBSTR,
    _OP_STRING_STRIDOF,
    _OP_REGEXP_EMPTY,
    _OP_REGEXP_FULL_CHAR,
    _OP_SEQ_SKOLEM,
    LAST_SEQ_OP
};


class zstring {
private:
    buffer<unsigned> m_buffer;
    bool well_formed() const;
public:
    static unsigned max_char() { return 196607; }
    zstring() {}
    zstring(char const* s);
    zstring(unsigned sz, unsigned const* s) { m_buffer.append(sz, s); SASSERT(well_formed()); }
    zstring(zstring const& other): m_buffer(other.m_buffer) {}
    zstring(unsigned num_bits, bool const* ch);
    zstring(unsigned ch);
    zstring& operator=(zstring const& other);
    zstring replace(zstring const& src, zstring const& dst) const;
    std::string encode() const;
    unsigned length() const { return m_buffer.size(); }
    unsigned operator[](unsigned i) const { return m_buffer[i]; }
    bool empty() const { return m_buffer.empty(); }
    bool suffixof(zstring const& other) const;
    bool prefixof(zstring const& other) const;
    bool contains(zstring const& other) const;
    int  indexofu(zstring const& other, unsigned offset) const;
    int  last_indexof(zstring const& other) const;
    zstring extract(unsigned lo, unsigned hi) const;
    zstring operator+(zstring const& other) const;
    bool operator==(const zstring& other) const;
    bool operator!=(const zstring& other) const;

    friend std::ostream& operator<<(std::ostream &os, const zstring &str);
    friend bool operator<(const zstring& lhs, const zstring& rhs);
};

class seq_decl_plugin : public decl_plugin {
    struct psig {
        symbol          m_name;
        unsigned        m_num_params;
        sort_ref_vector m_dom;
        sort_ref        m_range;
        psig(ast_manager& m, char const* name, unsigned n, unsigned dsz, sort* const* dom, sort* rng):
            m_name(name),
            m_num_params(n),
            m_dom(m),
            m_range(rng, m)
        {
            m_dom.append(dsz, dom);
        }
    };

    ptr_vector<psig> m_sigs;
    ptr_vector<sort> m_binding;
    bool             m_init;
    symbol           m_stringc_sym;
    symbol           m_charc_sym;
    sort*            m_string;
    sort*            m_char;
    sort*            m_reglan;
    bool             m_has_re;
    bool             m_has_seq;

    void match(psig& sig, unsigned dsz, sort* const* dom, sort* range, sort_ref& rng);

    void match_right_assoc(psig& sig, unsigned dsz, sort* const* dom, sort* range, sort_ref& rng);

    bool match(ptr_vector<sort>& binding, sort* s, sort* sP);

    sort* apply_binding(ptr_vector<sort> const& binding, sort* s);

    bool is_sort_param(sort* s, unsigned& idx);

    func_decl* mk_seq_fun(decl_kind k, unsigned arity, sort* const* domain, sort* range, decl_kind k_string);
    func_decl* mk_str_fun(decl_kind k, unsigned arity, sort* const* domain, sort* range, decl_kind k_seq);
    func_decl* mk_assoc_fun(decl_kind k, unsigned arity, sort* const* domain, sort* range, decl_kind k_string, decl_kind k_seq);

    void init();

    void set_manager(ast_manager * m, family_id id) override;

public:
    seq_decl_plugin();

    ~seq_decl_plugin() override {}
    void finalize() override;

    decl_plugin * mk_fresh() override { return alloc(seq_decl_plugin); }

    sort * mk_sort(decl_kind k, unsigned num_parameters, parameter const * parameters) override;

    func_decl * mk_func_decl(decl_kind k, unsigned num_parameters, parameter const * parameters,
                             unsigned arity, sort * const * domain, sort * range) override;

    void get_op_names(svector<builtin_name> & op_names, symbol const & logic) override;

    void get_sort_names(svector<builtin_name> & sort_names, symbol const & logic) override;

    bool is_value(app * e) const override;

    bool is_unique_value(app * e) const override { return false; }

    bool are_equal(app* a, app* b) const override;

    bool are_distinct(app* a, app* b) const override;

    expr * get_some_value(sort * s) override;

    bool is_char(ast* a) const { return a == m_char; }

    app* mk_string(symbol const& s);
    app* mk_string(zstring const& s);
    app* mk_char(unsigned ch);

    bool has_re() const { return m_has_re; }
    bool has_seq() const { return m_has_seq; }

    bool is_considered_uninterpreted(func_decl * f) override;
};

class seq_util {
    ast_manager& m;
    seq_decl_plugin& seq;
    family_id m_fid;
    mutable scoped_ptr<bv_util> m_bv;
    bv_util& bv() const;
public:

    ast_manager& get_manager() const { return m; }

    bool is_char(sort* s) const { return seq.is_char(s); }
    bool is_string(sort* s) const { return is_seq(s) && seq.is_char(s->get_parameter(0).get_ast()); }
    bool is_seq(sort* s) const { return is_sort_of(s, m_fid, SEQ_SORT); }
    bool is_re(sort* s) const { return is_sort_of(s, m_fid, RE_SORT); }
    bool is_re(sort* s, sort*& seq) const { return is_sort_of(s, m_fid, RE_SORT)  && (seq = to_sort(s->get_parameter(0).get_ast()), true); }
    bool is_seq(expr* e) const  { return is_seq(m.get_sort(e)); }
    bool is_seq(sort* s, sort*& seq) const { return is_seq(s) && (seq = to_sort(s->get_parameter(0).get_ast()), true); }
    bool is_re(expr* e) const { return is_re(m.get_sort(e)); }
    bool is_re(expr* e, sort*& seq) const { return is_re(m.get_sort(e), seq); }
    bool is_char(expr* e) const { return is_char(m.get_sort(e)); }
    bool is_const_char(expr* e, unsigned& c) const;
#if Z3_USE_UNICODE
    bool is_char_le(expr const* e) const { return is_app_of(e, m_fid, OP_CHAR_LE); }
#else
    bool is_char_le(expr const* e) const { return bv().is_bv_ule(e) && is_char(to_app(e)->get_arg(0)); }
#endif
    app* mk_char(unsigned ch) const;
    app* mk_le(expr* ch1, expr* ch2) const;
    app* mk_lt(expr* ch1, expr* ch2) const;

    app* mk_skolem(symbol const& name, unsigned n, expr* const* args, sort* range);
    bool is_skolem(expr const* e) const { return is_app_of(e, m_fid, _OP_SEQ_SKOLEM); }

    MATCH_BINARY(is_char_le);

    bool has_re() const { return seq.has_re(); }
    bool has_seq() const { return seq.has_seq(); }

    class str {
        seq_util&    u;
        ast_manager& m;
        family_id    m_fid;

        app* mk_string(char const* s) { return mk_string(symbol(s)); }
        app* mk_string(std::string const& s) { return mk_string(symbol(s.c_str())); }


    public:
        str(seq_util& u): u(u), m(u.m), m_fid(u.m_fid) {}

        sort* mk_seq(sort* s) const { parameter param(s); return m.mk_sort(m_fid, SEQ_SORT, 1, &param); }
        sort* mk_string_sort() const { return m.mk_sort(m_fid, _STRING_SORT, 0, nullptr); }
        app* mk_empty(sort* s) const { return m.mk_const(m.mk_func_decl(m_fid, OP_SEQ_EMPTY, 0, nullptr, 0, (expr*const*)nullptr, s)); }
        app* mk_string(zstring const& s) const;
        app* mk_string(symbol const& s) const { return u.seq.mk_string(s); }
        app* mk_char(unsigned ch) const;
        app* mk_concat(expr* a, expr* b) const { expr* es[2] = { a, b }; return m.mk_app(m_fid, OP_SEQ_CONCAT, 2, es); }
        app* mk_concat(expr* a, expr* b, expr* c) const { return mk_concat(a, mk_concat(b, c)); }
        expr* mk_concat(unsigned n, expr* const* es, sort* s) const { 
            if (n == 0) return mk_empty(s);
            if (n == 1) return es[0]; 
            return m.mk_app(m_fid, OP_SEQ_CONCAT, n, es); }
        expr* mk_concat(expr_ref_vector const& es, sort* s) const { return mk_concat(es.size(), es.c_ptr(), s); }
        app* mk_length(expr* a) const { return m.mk_app(m_fid, OP_SEQ_LENGTH, 1, &a); }
        app* mk_at(expr* s, expr* i) const { expr* es[2] = { s, i }; return m.mk_app(m_fid, OP_SEQ_AT, 2, es); }
        app* mk_nth(expr* s, expr* i) const { expr* es[2] = { s, i }; return m.mk_app(m_fid, OP_SEQ_NTH, 2, es); }
        app* mk_nth_i(expr* s, expr* i) const { expr* es[2] = { s, i }; return m.mk_app(m_fid, OP_SEQ_NTH_I, 2, es); }
        app* mk_nth_i(expr* s, unsigned i) const;

        app* mk_substr(expr* a, expr* b, expr* c) const { expr* es[3] = { a, b, c }; return m.mk_app(m_fid, OP_SEQ_EXTRACT, 3, es); }
        app* mk_contains(expr* a, expr* b) const { expr* es[2] = { a, b }; return m.mk_app(m_fid, OP_SEQ_CONTAINS, 2, es); }
        app* mk_prefix(expr* a, expr* b) const { expr* es[2] = { a, b }; return m.mk_app(m_fid, OP_SEQ_PREFIX, 2, es); }
        app* mk_suffix(expr* a, expr* b) const { expr* es[2] = { a, b }; return m.mk_app(m_fid, OP_SEQ_SUFFIX, 2, es); }
        app* mk_index(expr* a, expr* b, expr* i) const { expr* es[3] = { a, b, i}; return m.mk_app(m_fid, OP_SEQ_INDEX, 3, es); }
        app* mk_last_index(expr* a, expr* b) const { expr* es[2] = { a, b}; return m.mk_app(m_fid, OP_SEQ_LAST_INDEX, 2, es); }
        app* mk_replace(expr* a, expr* b, expr* c) const { expr* es[3] = { a, b, c}; return m.mk_app(m_fid, OP_SEQ_REPLACE, 3, es); }
        app* mk_unit(expr* u) const { return m.mk_app(m_fid, OP_SEQ_UNIT, 1, &u); }
        app* mk_char(zstring const& s, unsigned idx) const;
        app* mk_itos(expr* i) const { return m.mk_app(m_fid, OP_STRING_ITOS, 1, &i); }
        app* mk_stoi(expr* s) const { return m.mk_app(m_fid, OP_STRING_STOI, 1, &s); }
        app* mk_is_empty(expr* s) const;
        app* mk_lex_lt(expr* a, expr* b) const { expr* es[2] = { a, b }; return m.mk_app(m_fid, OP_STRING_LT, 2, es); }
        app* mk_lex_le(expr* a, expr* b) const { expr* es[2] = { a, b }; return m.mk_app(m_fid, OP_STRING_LE, 2, es); }
        app* mk_to_code(expr* e) const { return m.mk_app(m_fid, OP_STRING_TO_CODE, 1, &e); }
        app* mk_from_code(expr* e) const { return m.mk_app(m_fid, OP_STRING_FROM_CODE, 1, &e); }
        app* mk_is_digit(expr* e) const { return m.mk_app(m_fid, OP_STRING_IS_DIGIT, 1, &e); }


        bool is_nth_i(func_decl const* f)       const { return is_decl_of(f, m_fid, OP_SEQ_NTH_I); }
        bool is_nth_u(func_decl const* f)       const { return is_decl_of(f, m_fid, OP_SEQ_NTH_U); }
        bool is_skolem(func_decl const* f)      const { return is_decl_of(f, m_fid, _OP_SEQ_SKOLEM); }

        bool is_string(expr const * n) const { return is_app_of(n, m_fid, OP_STRING_CONST); }
        bool is_string(expr const* n, symbol& s) const {
            return is_string(n) && (s = to_app(n)->get_decl()->get_parameter(0).get_symbol(), true);
        }
        bool is_string(func_decl const* f) const { return is_decl_of(f, m_fid, OP_STRING_CONST); }
        bool is_string(expr const* n, zstring& s) const;
        bool is_string(func_decl const* f, zstring& s) const;
        bool is_empty(expr const* n) const { symbol s;
            return is_app_of(n, m_fid, OP_SEQ_EMPTY) || (is_string(n, s) && !s.is_numerical() && *s.bare_str() == 0);
        }
        bool is_concat(expr const* n)   const { return is_app_of(n, m_fid, OP_SEQ_CONCAT); }
        bool is_length(expr const* n)   const { return is_app_of(n, m_fid, OP_SEQ_LENGTH); }
        bool is_extract(expr const* n)  const { return is_app_of(n, m_fid, OP_SEQ_EXTRACT); }
        bool is_contains(expr const* n) const { return is_app_of(n, m_fid, OP_SEQ_CONTAINS); }
        bool is_at(expr const* n)       const { return is_app_of(n, m_fid, OP_SEQ_AT); }
        bool is_nth_i(expr const* n)       const { return is_app_of(n, m_fid, OP_SEQ_NTH_I); }
        bool is_nth_u(expr const* n)       const { return is_app_of(n, m_fid, OP_SEQ_NTH_U); }
        bool is_nth_i(expr const* n, expr*& s, unsigned& idx) const;
        bool is_index(expr const* n)    const { return is_app_of(n, m_fid, OP_SEQ_INDEX); }
        bool is_last_index(expr const* n)    const { return is_app_of(n, m_fid, OP_SEQ_LAST_INDEX); }
        bool is_replace(expr const* n)  const { return is_app_of(n, m_fid, OP_SEQ_REPLACE); }
        bool is_replace_re(expr const* n)  const { return is_app_of(n, m_fid, OP_SEQ_REPLACE_RE); }
        bool is_replace_re_all(expr const* n)  const { return is_app_of(n, m_fid, OP_SEQ_REPLACE_RE_ALL); }
        bool is_replace_all(expr const* n)  const { return is_app_of(n, m_fid, OP_SEQ_REPLACE_ALL); }
        bool is_prefix(expr const* n)   const { return is_app_of(n, m_fid, OP_SEQ_PREFIX); }
        bool is_suffix(expr const* n)   const { return is_app_of(n, m_fid, OP_SEQ_SUFFIX); }
        bool is_itos(expr const* n)     const { return is_app_of(n, m_fid, OP_STRING_ITOS); }
        bool is_stoi(expr const* n)     const { return is_app_of(n, m_fid, OP_STRING_STOI); }
        bool is_in_re(expr const* n)    const { return is_app_of(n, m_fid, OP_SEQ_IN_RE); }
        bool is_unit(expr const* n)     const { return is_app_of(n, m_fid, OP_SEQ_UNIT); }
        bool is_lt(expr const* n)       const { return is_app_of(n, m_fid, OP_STRING_LT); }
        bool is_le(expr const* n)       const { return is_app_of(n, m_fid, OP_STRING_LE); }
        bool is_is_digit(expr const* n) const { return is_app_of(n, m_fid, OP_STRING_IS_DIGIT); }
        bool is_from_code(expr const* n) const { return is_app_of(n, m_fid, OP_STRING_TO_CODE); }
        bool is_to_code(expr const* n) const { return is_app_of(n, m_fid, OP_STRING_FROM_CODE); }

        bool is_string_term(expr const * n) const {
            sort * s = get_sort(n);
            return u.is_string(s);
        }

        bool is_non_string_sequence(expr const * n) const {
            sort * s = get_sort(n);
            return (u.is_seq(s) && !u.is_string(s));
        }

        MATCH_BINARY(is_concat);
        MATCH_UNARY(is_length);
        MATCH_TERNARY(is_extract);
        MATCH_BINARY(is_contains);
        MATCH_BINARY(is_at);
        MATCH_BINARY(is_nth_i);
        MATCH_BINARY(is_nth_u);
        MATCH_BINARY(is_index);
        MATCH_TERNARY(is_index);
        MATCH_BINARY(is_last_index);
        MATCH_TERNARY(is_replace);
        MATCH_TERNARY(is_replace_re);
        MATCH_TERNARY(is_replace_re_all);
        MATCH_TERNARY(is_replace_all);
        MATCH_BINARY(is_prefix);
        MATCH_BINARY(is_suffix);
        MATCH_BINARY(is_lt);
        MATCH_BINARY(is_le);
        MATCH_UNARY(is_itos);
        MATCH_UNARY(is_stoi);
        MATCH_UNARY(is_is_digit);
        MATCH_UNARY(is_from_code);
        MATCH_UNARY(is_to_code);
        MATCH_BINARY(is_in_re);
        MATCH_UNARY(is_unit);

        void get_concat(expr* e, expr_ref_vector& es) const;
        void get_concat_units(expr* e, expr_ref_vector& es) const;
        expr* get_leftmost_concat(expr* e) const { expr* e1, *e2; while (is_concat(e, e1, e2)) e = e1; return e; }
        expr* get_rightmost_concat(expr* e) const { expr* e1, *e2; while (is_concat(e, e1, e2)) e = e2; return e; }

        unsigned min_length(expr* s) const;
    };

    class re {
        seq_util&    u;
        ast_manager& m;
        family_id    m_fid;
    public:
        re(seq_util& u): u(u), m(u.m), m_fid(u.m_fid) {}

        sort* mk_re(sort* seq) { parameter param(seq); return m.mk_sort(m_fid, RE_SORT, 1, &param); }
        sort* to_seq(sort* re);

        app* mk_to_re(expr* s) { return m.mk_app(m_fid, OP_SEQ_TO_RE, 1, &s); }
        app* mk_in_re(expr* s, expr* r) { return m.mk_app(m_fid, OP_SEQ_IN_RE, s, r); }
        app* mk_range(expr* s1, expr* s2) { return m.mk_app(m_fid, OP_RE_RANGE, s1, s2); }
        app* mk_concat(expr* r1, expr* r2) { return m.mk_app(m_fid, OP_RE_CONCAT, r1, r2); }
        app* mk_union(expr* r1, expr* r2) { return m.mk_app(m_fid, OP_RE_UNION, r1, r2); }
        app* mk_inter(expr* r1, expr* r2) { return m.mk_app(m_fid, OP_RE_INTERSECT, r1, r2); }
        app* mk_diff(expr* r1, expr* r2) { return m.mk_app(m_fid, OP_RE_DIFF, r1, r2); }
        app* mk_complement(expr* r) { return m.mk_app(m_fid, OP_RE_COMPLEMENT, r); }
        app* mk_star(expr* r) { return m.mk_app(m_fid, OP_RE_STAR, r); }
        app* mk_plus(expr* r) { return m.mk_app(m_fid, OP_RE_PLUS, r); }
        app* mk_opt(expr* r) { return m.mk_app(m_fid, OP_RE_OPTION, r); }
        app* mk_loop(expr* r, unsigned lo);
        app* mk_loop(expr* r, unsigned lo, unsigned hi);
        app* mk_loop(expr* r, expr* lo);
        app* mk_loop(expr* r, expr* lo, expr* hi);
        app* mk_full_char(sort* s);
        app* mk_full_seq(sort* s);
        app* mk_empty(sort* s);
        app* mk_of_pred(expr* p);

        bool is_to_re(expr const* n)    const { return is_app_of(n, m_fid, OP_SEQ_TO_RE); }
        bool is_concat(expr const* n)    const { return is_app_of(n, m_fid, OP_RE_CONCAT); }
        bool is_union(expr const* n)    const { return is_app_of(n, m_fid, OP_RE_UNION); }
        bool is_intersection(expr const* n)    const { return is_app_of(n, m_fid, OP_RE_INTERSECT); }
        bool is_diff(expr const* n)    const { return is_app_of(n, m_fid, OP_RE_DIFF); }
        bool is_complement(expr const* n)    const { return is_app_of(n, m_fid, OP_RE_COMPLEMENT); }
        bool is_star(expr const* n)    const { return is_app_of(n, m_fid, OP_RE_STAR); }
        bool is_plus(expr const* n)    const { return is_app_of(n, m_fid, OP_RE_PLUS); }
        bool is_opt(expr const* n)    const { return is_app_of(n, m_fid, OP_RE_OPTION); }
        bool is_range(expr const* n)    const { return is_app_of(n, m_fid, OP_RE_RANGE); }
        bool is_loop(expr const* n)    const { return is_app_of(n, m_fid, OP_RE_LOOP); }
        bool is_empty(expr const* n)  const { return is_app_of(n, m_fid, OP_RE_EMPTY_SET); }
        bool is_full_char(expr const* n)  const { return is_app_of(n, m_fid, OP_RE_FULL_CHAR_SET); }
        bool is_full_seq(expr const* n)  const { return is_app_of(n, m_fid, OP_RE_FULL_SEQ_SET); }
        bool is_of_pred(expr const* n) const { return is_app_of(n, m_fid, OP_RE_OF_PRED); }
        MATCH_UNARY(is_to_re);
        MATCH_BINARY(is_concat);
        MATCH_BINARY(is_union);
        MATCH_BINARY(is_intersection);
        MATCH_BINARY(is_diff);
        MATCH_BINARY(is_range);
        MATCH_UNARY(is_complement);
        MATCH_UNARY(is_star);
        MATCH_UNARY(is_plus);
        MATCH_UNARY(is_opt);
        MATCH_UNARY(is_of_pred);
        bool is_loop(expr const* n, expr*& body, unsigned& lo, unsigned& hi);
        bool is_loop(expr const* n, expr*& body, unsigned& lo);
        bool is_loop(expr const* n, expr*& body, expr*& lo, expr*& hi);
        bool is_loop(expr const* n, expr*& body, expr*& lo);
        unsigned min_length(expr* r) const;
    };
    str str;
    re  re;

    seq_util(ast_manager& m):
        m(m),
        seq(*static_cast<seq_decl_plugin*>(m.get_plugin(m.mk_family_id("seq")))),
        m_fid(seq.get_family_id()),
        str(*this),
        re(*this) {
    }

    ~seq_util() {}

    family_id get_family_id() const { return m_fid; }

};

#endif /* SEQ_DECL_PLUGIN_H_ */

