Hi, I tried this very confuse code, and I am happy if somebody could help-me. I tried to make covariant derivative derivated from a indexed. Use it like: D(indexed(A,mu),nu) But the fatal errors in this code (among millions..): i) simplify_indexed() crashs or doesnt work !! II) get_free_indexes not work, so D^\alpha(A_beta)A^\beta A_\alpha -D^\beta(A_alpha)A^\beta A_\alpha is not zero In the last post , Christian Bauer suggests "override is eval_indexed() (for automatic evaluation) and contract_with()/add_indexed()/scalar_mul_indexed() (for manual evaluation, AKA simplify_indexed())" and showed the way: look color.cpp source. Any suggestions are welcome Marco #include <iostream> #include <ginac/ginac.h> #define N 4 #define N1 8 using namespace std; using namespace GiNaC; const unsigned TINFO_covdiff = 0x42420001U; class covdiff : public indexed { GINAC_DECLARE_REGISTERED_CLASS(covdiff, indexed) public: covdiff(const ex & b,const ex & i1); covdiff(const ex & b, const ex & i1, const ex & i2); covdiff(const ex & b, const ex & i1, const ex & i2,const ex & i3); covdiff(const ex & b, const ex & i1, const ex & i2,const ex & i3, const ex & i4); covdiff(const ex & b, const lst & iv); size_t nops() const; ex op(size_t i) const; ex & let_op(size_t i); ex subs(const exmap & m, unsigned options) const; protected: void do_print(const print_context & c, unsigned level) const; ex symtree, arg,index; lst seq; }; GINAC_IMPLEMENT_REGISTERED_CLASS_OPT(covdiff, indexed, print_func<print_context>(&covdiff::do_print)) covdiff::covdiff(const ex & b, const ex & i1) : inherited(b, i1),arg(b),index(i1), symtree(not_symmetric()) { tinfo_key = TINFO_covdiff; } covdiff::covdiff(const ex & b, const ex & i1, const ex & i2) : inherited(b, i1, i2),arg(b), symtree(not_symmetric()) { seq =i1,i2; tinfo_key = TINFO_covdiff; } covdiff::covdiff(const ex & b, const ex & i1, const ex & i2, const ex & i3) : inherited(b, i1, i2, i3),arg(b), symtree(not_symmetric()) { seq=i1,i2,i3; tinfo_key = TINFO_covdiff; } covdiff::covdiff(const ex & b, const ex & i1, const ex & i2, const ex & i3, const ex & i4) : inherited(b, i1, i2, i3, i4),arg(b), symtree(not_symmetric()) {seq = i1,i2,i3,i4; tinfo_key = TINFO_covdiff; } covdiff::covdiff(const ex & b, const lst & iv) : inherited(b),arg(b), symtree(not_symmetric()) { seq=iv; tinfo_key = TINFO_covdiff; } //archiving covdiff::covdiff(const archive_node &n, lst &sym_lst) : inherited(n, sym_lst) { if (!n.find_ex("symmetry", symtree, sym_lst)) { // GiNaC versions <= 0.9.0 had an unsigned "symmetry" property unsigned symm = 0; n.find_unsigned("symmetry", symm); switch (symm) { case 1: symtree = sy_symm(); break; case 2: symtree = sy_anti(); break; default: symtree = not_symmetric(); break; } const_cast<symmetry &>(ex_to<symmetry>(symtree)).validate(seq.nops() - 1); } } void covdiff::archive(archive_node &n) const { inherited::archive(n); n.add_ex("symmetry", symtree); } ex covdiff::unarchive(const archive_node &n, lst &sym_lst) { return (new covdiff(n, sym_lst))->setflag(status_flags::dynallocated); } //comparation method void covdiff::do_print(const print_context & c, unsigned level) const { if (is_a<print_tree>(c)) covdiff::print(c,level); if (seq.nops() > 1) { for( lst::const_iterator it=seq.begin();it != seq.end();++it) c.s<<"D"<<*it; c.s<<"("<<arg<<")"; } else c.s << "D"<<index <<" ("<<arg<<")"; } int covdiff::compare_same_type(const basic & other) const { GINAC_ASSERT(is_a<covdiff>(other)); return inherited::compare_same_type(other); } ex covdiff::op(size_t i) const{ if(i==0) return arg; if(seq.nops() > 0 && i != 0) return seq[i-1]; if(seq.nops()==0 && i==1) return index; else throw std::range_error("covdiff::let_op(): no such operand"); } size_t covdiff::nops() const { if(seq.nops()>0) return seq.nops()+1; else return 2; } ex & covdiff:: let_op(size_t i) { ensure_if_modifiable(); if(i==0) return arg; if(seq.nops() > 0 && i != 0) return seq[i-1]; if(seq.nops()==0 && i==1) return index; else throw std::range_error("covdiff::let_op(): no such operand"); } ex covdiff::subs(const exmap & m, unsigned options) const { size_t num = nops(); if (num) { // Substitute in subexpressions for (size_t i=0; i<num; i++) { const ex & orig_op = op(i); const ex & subsed_op = orig_op.subs(m, options); if (!are_ex_trivially_equal(orig_op, subsed_op)) { // Something changed, clone the object basic *copy = duplicate(); copy->setflag(status_flags::dynallocated); copy->clearflag(status_flags::hash_calculated | status_flags::expanded); // Substitute the changed operand copy->let_op(i++) = subsed_op; // Substitute the other operands for (; i<num; i++) copy->let_op(i) = op(i).subs(m, options); // Perform substitutions on the new object as a whole return copy->subs_one_level(m, options); } } } // Nothing changed or no subexpressions return subs_one_level(m, options); } ex Derivative_helper(ex e, ex var) { lst iv; if(is_a<covdiff>(e)){ for(size_t i=1; i<e.nops();i++) iv.append(e.op(i)); iv.append(var); return covdiff(e.op(0),iv); }else if(is_a<indexed>(e)){ if(is_a<su3f>(e.op(0)) && e.nops()==4) return 0; else return covdiff(e,var); } else return 0; } struct make_diff : public map_function{ ex var; make_diff(ex var_): var(var_){} ex operator()(const ex & e) { if(is_a<add>(e)) return e.map(*this); else if(is_a<mul>(e)) { ex result =0; for(size_t i=0;i<e.nops();++i) { result +=e.subs(e.op(i)==Derivative_helper(e.op(i),var)); }; return result; }else return Derivative_helper(e,var); } }; ex D(ex e, ex index){ ex result; make_diff D(index); return D(e); } ------------------------------------------------- This mail sent through IMP: http://horde.org/imp/