[GiNaC-list] A strange behaviour while implementing archive in a user-defined class

[Vladimir V. Kisil]

>>>>> On Sat, 18 Dec 2021 16:22:22 +0800, Feng Feng <f.feng at outlook.com> said:
    FF> I got a strange behaviour while implementing the archive in
    FF> user-defined class, to make the behaviour more explicitly, let

    If you will delete the method Symbol::calchash() from your class you
  will get the expected behaviour.
-- 
Vladimir V. Kisil                 http://www.maths.leeds.ac.uk/~kisilv/
  Book:      Geometry of Mobius Maps       https://doi.org/10.1142/p835
  Soft:      Geometry of cycles         http://moebinv.sourceforge.net/
  Jupyter notebooks:        https://github.com/vvkisil?tab=repositories
>>>>> On Sat, 18 Dec 2021 16:22:22 +0800, Feng Feng <f.feng at outlook.com> said:

    FF> Dear all,


    FF> I got a strange behaviour while implementing the archive in
    FF> user-defined class, to make the behaviour more explicitly, let
    FF> me post the C++ code here:


    FF> #include <ginac/ginac.h> #include <fstream>


    FF> using namespace GiNaC; using namespace std;


    FF> class Symbol : public symbol {
    FF> GINAC_DECLARE_REGISTERED_CLASS(Symbol, symbol) public:
    FF> Symbol(const string &s); void archive(archive_node & n) const
    FF> override; void read_archive(const archive_node& n, lst& sym_lst)
    FF> override; unsigned calchash() const override; };
    FF> GINAC_DECLARE_UNARCHIVER(Symbol);


    FF> GINAC_IMPLEMENT_REGISTERED_CLASS(Symbol, symbol)
    FF> GINAC_BIND_UNARCHIVER(Symbol);


    FF> const symbol & get_symbol(const string & s) { static map<string,
    FF> symbol> dict; if (dict.find(s) == dict.end()) dict[s] =
    FF> symbol(s); return dict[s]; }


    FF> Symbol::Symbol() { } Symbol::Symbol(const string &s) :
    FF> symbol(get_symbol(s)) { } int Symbol::compare_same_type(const
    FF> basic &other) const { const Symbol &o = static_cast<const Symbol
    FF> &>(other); int ret = get_name().compare(o.get_name());
    FF> if(ret==0) return 0; else if(ret<0) return -1; else return 1; }
 
    FF> void Symbol::archive(archive_node & n) const {
    FF> inherited::archive(n); }
    
    FF> void Symbol::read_archive(const archive_node& n, lst& sym_lst) {
    FF> inherited::read_archive(n, sym_lst); *this = Symbol(get_name());
    FF> }


    FF> unsigned Symbol::calchash() const { static auto hash =
    FF> symbol("_").gethash(); return hash; }


    FF> int main() { Symbol k1("k1"), k2("k2"); auto garfn = "tmp.gar";
    
    FF>     { archive ar; ex val = lst{ k1*k1, k2*k2 };
    FF> ar.archive_ex(val, "key"); ofstream out(garfn); out << ar;
    FF> out.close(); cout << "writed: " << val << endl; } { archive ar;
    FF> ifstream in(garfn); in >> ar; in.close(); auto val =
    FF> ar.unarchive_ex(lst{}, "key"); cout << "read: " << val << endl;
    FF> } // console output is // writed: {k1^2,k2^2} // read:
    FF> {k1^2,k2^2}
    
    FF>     { archive ar; ex val = lst{ k1*k1==0, k2*k2==0 };
    FF> ar.archive_ex(val, "key"); ofstream out(garfn); out << ar;
    FF> out.close(); cout << "writed: " << val << endl; } { archive ar;
    FF> ifstream in(garfn); in >> ar; in.close(); auto val =
    FF> ar.unarchive_ex(lst{}, "key"); cout << "read: " << val << endl;
    FF> } // console output is // writed: {k1^2==0,k2^2==0} // read:
    FF> {k1^2==0,k1^2==0} // Note that the last line above, both items
    FF> are the same: k1^2==0
    
    FF>     return 0; }


    FF> Here I want to introduce a class Symbol, when one defines Symbol
    FF> a(“a”), b(“a”);, then a and b will be the same or equal, so I
    FF> override the method compare_same_type.




    FF> The last console output seems very strange to me, the both items
    FF> are the same, while the expected result is "read:
    FF> {k1^2==0,k2^2==0}”.


    FF> Thanks very much!


    FF> Best regards!  Feng

    FF> ----------------------------------------------------
    FF> Alternatives:

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