]> www.ginac.de Git - ginac.git/blobdiff - ginac/ncmul.cpp
Finalize 1.7.6 release.
[ginac.git] / ginac / ncmul.cpp
index 21cdefda7ccfb3e3d1c48d8268d11e9f0f957ff4..f086e49235568573d19f5513dad93b930c8e79c6 100644 (file)
@@ -3,7 +3,7 @@
  *  Implementation of GiNaC's non-commutative products of expressions. */
 
 /*
- *  GiNaC Copyright (C) 1999-2001 Johannes Gutenberg University Mainz, Germany
+ *  GiNaC Copyright (C) 1999-2019 Johannes Gutenberg University Mainz, Germany
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
  *
  *  You should have received a copy of the GNU General Public License
  *  along with this program; if not, write to the Free Software
- *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  */
 
-#include <algorithm>
-#include <iostream>
-#include <stdexcept>
-
 #include "ncmul.h"
 #include "ex.h"
 #include "add.h"
 #include "mul.h"
+#include "clifford.h"
 #include "matrix.h"
-#include "print.h"
 #include "archive.h"
-#include "debugmsg.h"
+#include "indexed.h"
 #include "utils.h"
 
+#include <algorithm>
+#include <iostream>
+#include <stdexcept>
+
 namespace GiNaC {
 
-GINAC_IMPLEMENT_REGISTERED_CLASS(ncmul, exprseq)
+GINAC_IMPLEMENT_REGISTERED_CLASS_OPT(ncmul, exprseq,
+  print_func<print_context>(&ncmul::do_print).
+  print_func<print_tree>(&ncmul::do_print_tree).
+  print_func<print_csrc>(&ncmul::do_print_csrc).
+  print_func<print_python_repr>(&ncmul::do_print_csrc))
+
 
 //////////
-// default constructor, destructor, copy constructor assignment operator and helpers
+// default constructor
 //////////
 
 ncmul::ncmul()
 {
-       debugmsg("ncmul default constructor",LOGLEVEL_CONSTRUCT);
-       tinfo_key = TINFO_ncmul;
 }
 
-DEFAULT_COPY(ncmul)
-DEFAULT_DESTROY(ncmul)
-
 //////////
 // other constructors
 //////////
 
 // public
 
-ncmul::ncmul(const ex & lh, const ex & rh) : inherited(lh,rh)
+ncmul::ncmul(const ex & lh, const ex & rh) : inherited{lh,rh}
 {
-       debugmsg("ncmul constructor from ex,ex",LOGLEVEL_CONSTRUCT);
-       tinfo_key = TINFO_ncmul;
 }
 
-ncmul::ncmul(const ex & f1, const ex & f2, const ex & f3) : inherited(f1,f2,f3)
+ncmul::ncmul(const ex & f1, const ex & f2, const ex & f3) : inherited{f1,f2,f3}
 {
-       debugmsg("ncmul constructor from 3 ex",LOGLEVEL_CONSTRUCT);
-       tinfo_key = TINFO_ncmul;
 }
 
 ncmul::ncmul(const ex & f1, const ex & f2, const ex & f3,
-             const ex & f4) : inherited(f1,f2,f3,f4)
+             const ex & f4) : inherited{f1,f2,f3,f4}
 {
-       debugmsg("ncmul constructor from 4 ex",LOGLEVEL_CONSTRUCT);
-       tinfo_key = TINFO_ncmul;
 }
 
 ncmul::ncmul(const ex & f1, const ex & f2, const ex & f3,
-             const ex & f4, const ex & f5) : inherited(f1,f2,f3,f4,f5)
+             const ex & f4, const ex & f5) : inherited{f1,f2,f3,f4,f5}
 {
-       debugmsg("ncmul constructor from 5 ex",LOGLEVEL_CONSTRUCT);
-       tinfo_key = TINFO_ncmul;
 }
 
 ncmul::ncmul(const ex & f1, const ex & f2, const ex & f3,
-             const ex & f4, const ex & f5, const ex & f6) : inherited(f1,f2,f3,f4,f5,f6)
+             const ex & f4, const ex & f5, const ex & f6) : inherited{f1,f2,f3,f4,f5,f6}
 {
-       debugmsg("ncmul constructor from 6 ex",LOGLEVEL_CONSTRUCT);
-       tinfo_key = TINFO_ncmul;
 }
 
-ncmul::ncmul(const exvector & v, bool discardable) : inherited(v,discardable)
+ncmul::ncmul(const exvector & v) : inherited(v)
 {
-       debugmsg("ncmul constructor from exvector,bool",LOGLEVEL_CONSTRUCT);
-       tinfo_key = TINFO_ncmul;
 }
 
-ncmul::ncmul(exvector * vp) : inherited(vp)
+ncmul::ncmul(exvector && v) : inherited(std::move(v))
 {
-       debugmsg("ncmul constructor from exvector *",LOGLEVEL_CONSTRUCT);
-       tinfo_key = TINFO_ncmul;
 }
 
 //////////
 // archiving
 //////////
 
-DEFAULT_ARCHIVING(ncmul)
-       
+
 //////////
 // functions overriding virtual functions from base classes
 //////////
 
 // public
 
-void ncmul::print(const print_context & c, unsigned level) const
+void ncmul::do_print(const print_context & c, unsigned level) const
 {
-       debugmsg("ncmul print", LOGLEVEL_PRINT);
-
-       if (is_a<print_tree>(c)) {
-
-               inherited::print(c, level);
-
-       } else if (is_a<print_csrc>(c)) {
-
-               c.s << "ncmul(";
-               exvector::const_iterator it = seq.begin(), itend = seq.end()-1;
-               while (it != itend) {
-                       it->print(c, precedence());
-                       c.s << ",";
-                       it++;
-               }
-               it->print(c, precedence());
-               c.s << ")";
+       printseq(c, '(', '*', ')', precedence(), level);
+}
 
-       } else
-               printseq(c, '(', '*', ')', precedence(), level);
+void ncmul::do_print_csrc(const print_context & c, unsigned level) const
+{
+       c.s << class_name();
+       printseq(c, '(', ',', ')', precedence(), precedence());
 }
 
 bool ncmul::info(unsigned inf) const
@@ -143,27 +115,27 @@ bool ncmul::info(unsigned inf) const
        return inherited::info(inf);
 }
 
-typedef std::vector<int> intvector;
+typedef std::vector<std::size_t> uintvector;
 
 ex ncmul::expand(unsigned options) const
 {
        // First, expand the children
-       exvector expanded_seq = expandchildren(options);
+       exvector v = expandchildren(options);
+       const exvector &expanded_seq = v.empty() ? this->seq : v;
        
        // Now, look for all the factors that are sums and remember their
        // position and number of terms.
-       intvector positions_of_adds(expanded_seq.size());
-       intvector number_of_add_operands(expanded_seq.size());
+       uintvector positions_of_adds(expanded_seq.size());
+       uintvector number_of_add_operands(expanded_seq.size());
 
-       int number_of_adds = 0;
-       int number_of_expanded_terms = 1;
+       size_t number_of_adds = 0;
+       size_t number_of_expanded_terms = 1;
 
-       unsigned current_position = 0;
-       exvector::const_iterator last = expanded_seq.end();
-       for (exvector::const_iterator cit=expanded_seq.begin(); cit!=last; ++cit) {
-               if (is_exactly_a<add>(*cit)) {
+       size_t current_position = 0;
+       for (auto & it : expanded_seq) {
+               if (is_exactly_a<add>(it)) {
                        positions_of_adds[number_of_adds] = current_position;
-                       unsigned num_ops = cit->nops();
+                       size_t num_ops = it.nops();
                        number_of_add_operands[number_of_adds] = num_ops;
                        number_of_expanded_terms *= num_ops;
                        number_of_adds++;
@@ -172,23 +144,41 @@ ex ncmul::expand(unsigned options) const
        }
 
        // If there are no sums, we are done
-       if (number_of_adds == 0)
-               return (new ncmul(expanded_seq, true))->
-                       setflag(status_flags::dynallocated | (options == 0 ? status_flags::expanded : 0));
+       if (number_of_adds == 0) {
+               if (!v.empty())
+                       return dynallocate<ncmul>(std::move(v)).setflag(options == 0 ? status_flags::expanded : 0);
+               else
+                       return *this;
+       }
 
        // Now, form all possible products of the terms of the sums with the
        // remaining factors, and add them together
        exvector distrseq;
        distrseq.reserve(number_of_expanded_terms);
 
-       intvector k(number_of_adds);
+       uintvector k(number_of_adds);
+
+       /* Rename indices in the static members of the product */
+       exvector expanded_seq_mod;
+       size_t j = 0;
+       exvector va;
+
+       for (size_t i=0; i<expanded_seq.size(); i++) {
+               if (i == positions_of_adds[j]) {
+                       expanded_seq_mod.push_back(_ex1);
+                       j++;
+               } else {
+                       expanded_seq_mod.push_back(rename_dummy_indices_uniquely(va, expanded_seq[i], true));
+               }
+       }
 
        while (true) {
-               exvector term = expanded_seq;
-               for (int i=0; i<number_of_adds; i++)
-                       term[positions_of_adds[i]] = expanded_seq[positions_of_adds[i]].op(k[i]);
-               distrseq.push_back((new ncmul(term, true))->
-                                   setflag(status_flags::dynallocated | (options == 0 ? status_flags::expanded : 0)));
+               exvector term = expanded_seq_mod;
+               for (size_t i=0; i<number_of_adds; i++) {
+                       term[positions_of_adds[i]] = rename_dummy_indices_uniquely(va, expanded_seq[positions_of_adds[i]].op(k[i]), true);
+               }
+
+               distrseq.push_back(dynallocate<ncmul>(std::move(term)).setflag(options == 0 ? status_flags::expanded : 0));
 
                // increment k[]
                int l = number_of_adds-1;
@@ -200,74 +190,72 @@ ex ncmul::expand(unsigned options) const
                        break;
        }
 
-       return (new add(distrseq))->
-               setflag(status_flags::dynallocated | (options == 0 ? status_flags::expanded : 0));
+       return dynallocate<add>(distrseq).setflag(options == 0 ? status_flags::expanded : 0);
 }
 
 int ncmul::degree(const ex & s) const
 {
+       if (is_equal(ex_to<basic>(s)))
+               return 1;
+
        // Sum up degrees of factors
        int deg_sum = 0;
-       exvector::const_iterator i = seq.begin(), end = seq.end();
-       while (i != end) {
-               deg_sum += i->degree(s);
-               ++i;
-       }
+       for (auto & i : seq)
+               deg_sum += i.degree(s);
        return deg_sum;
 }
 
 int ncmul::ldegree(const ex & s) const
 {
+       if (is_equal(ex_to<basic>(s)))
+               return 1;
+
        // Sum up degrees of factors
        int deg_sum = 0;
-       exvector::const_iterator i = seq.begin(), end = seq.end();
-       while (i != end) {
-               deg_sum += i->degree(s);
-               ++i;
-       }
+       for (auto & i : seq)
+               deg_sum += i.degree(s);
        return deg_sum;
 }
 
 ex ncmul::coeff(const ex & s, int n) const
 {
+       if (is_equal(ex_to<basic>(s)))
+               return n==1 ? _ex1 : _ex0;
+
        exvector coeffseq;
        coeffseq.reserve(seq.size());
 
        if (n == 0) {
                // product of individual coeffs
                // if a non-zero power of s is found, the resulting product will be 0
-               exvector::const_iterator it=seq.begin();
-               while (it!=seq.end()) {
-                       coeffseq.push_back((*it).coeff(s,n));
-                       ++it;
-               }
-               return (new ncmul(coeffseq,1))->setflag(status_flags::dynallocated);
+               for (auto & it : seq)
+                       coeffseq.push_back(it.coeff(s,n));
+               return dynallocate<ncmul>(std::move(coeffseq));
        }
                 
-       exvector::const_iterator i = seq.begin(), end = seq.end();
        bool coeff_found = false;
-       while (i != end) {
-               ex c = i->coeff(s,n);
+       for (auto & i : seq) {
+               ex c = i.coeff(s,n);
                if (c.is_zero()) {
-                       coeffseq.push_back(*i);
+                       coeffseq.push_back(i);
                } else {
                        coeffseq.push_back(c);
                        coeff_found = true;
                }
-               ++i;
        }
 
-       if (coeff_found) return (new ncmul(coeffseq,1))->setflag(status_flags::dynallocated);
+       if (coeff_found)
+               return dynallocate<ncmul>(std::move(coeffseq));
        
        return _ex0;
 }
 
-unsigned ncmul::count_factors(const ex & e) const
+size_t ncmul::count_factors(const ex & e) const
 {
-       if ((is_ex_exactly_of_type(e,mul)&&(e.return_type()!=return_types::commutative))||
-               (is_ex_exactly_of_type(e,ncmul))) {
-               unsigned factors=0;
-               for (unsigned i=0; i<e.nops(); i++)
+       if ((is_exactly_a<mul>(e)&&(e.return_type()!=return_types::commutative))||
+               (is_exactly_a<ncmul>(e))) {
+               size_t factors=0;
+               for (size_t i=0; i<e.nops(); i++)
                        factors += count_factors(e.op(i));
                
                return factors;
@@ -277,10 +265,10 @@ unsigned ncmul::count_factors(const ex & e) const
                
 void ncmul::append_factors(exvector & v, const ex & e) const
 {
-       if ((is_ex_exactly_of_type(e,mul)&&(e.return_type()!=return_types::commutative))||
-               (is_ex_exactly_of_type(e,ncmul))) {
-               for (unsigned i=0; i<e.nops(); i++)
-                       append_factors(v,e.op(i));
+       if ((is_exactly_a<mul>(e)&&(e.return_type()!=return_types::commutative))||
+               (is_exactly_a<ncmul>(e))) {
+               for (size_t i=0; i<e.nops(); i++)
+                       append_factors(v, e.op(i));
        } else 
                v.push_back(e);
 }
@@ -296,10 +284,9 @@ typedef std::vector<exvector> exvectorvector;
  *  - ncmul() -> 1
  *  - ncmul(...,c1,...,c2,...) -> *(c1,c2,ncmul(...))  (pull out commutative elements)
  *  - ncmul(x1,y1,x2,y2) -> *(ncmul(x1,x2),ncmul(y1,y2))  (collect elements of same type)
- *  - ncmul(x1,x2,x3,...) -> x::simplify_ncmul(x1,x2,x3,...)
- *
- *  @param level cut-off in recursive evaluation */
-ex ncmul::eval(int level) const
+ *  - ncmul(x1,x2,x3,...) -> x::eval_ncmul(x1,x2,x3,...)
+ */
+ex ncmul::eval() const
 {
        // The following additional rule would be nice, but produces a recursion,
        // which must be trapped by introducing a flag that the sub-ncmuls()
@@ -308,24 +295,23 @@ ex ncmul::eval(int level) const
        //                      ncmul(ncmul(x1,x2,...),X,ncmul(y1,y2,...)
        //                      (X noncommutative_composite)
 
-       if ((level==1) && (flags & status_flags::evaluated)) {
+       if (flags & status_flags::evaluated) {
                return *this;
        }
 
-       exvector evaledseq=evalchildren(level);
-
        // ncmul(...,*(x1,x2),...,ncmul(x3,x4),...) ->
        //     ncmul(...,x1,x2,...,x3,x4,...)  (associativity)
-       unsigned factors = 0;
-       exvector::const_iterator cit = evaledseq.begin(), citend = evaledseq.end();
-       while (cit != citend)
-               factors += count_factors(*cit++);
+       size_t factors = 0;
+       for (auto & it : seq)
+               factors += count_factors(it);
        
        exvector assocseq;
        assocseq.reserve(factors);
-       cit = evaledseq.begin();
-       while (cit != citend)
-               append_factors(assocseq, *cit++);
+       make_flat_inserter mf(seq, true);
+       for (auto & it : seq) {
+               ex factor = mf.handle_factor(it, 1);
+               append_factors(assocseq, factor);
+       }
        
        // ncmul(x) -> x
        if (assocseq.size()==1) return *(seq.begin());
@@ -334,15 +320,14 @@ ex ncmul::eval(int level) const
        if (assocseq.empty()) return _ex1;
 
        // determine return types
-       unsignedvector rettypes;
-       rettypes.reserve(assocseq.size());
-       unsigned i = 0;
-       unsigned count_commutative=0;
-       unsigned count_noncommutative=0;
-       unsigned count_noncommutative_composite=0;
-       cit = assocseq.begin(); citend = assocseq.end();
-       while (cit != citend) {
-               switch (rettypes[i] = cit->return_type()) {
+       unsignedvector rettypes(assocseq.size());
+       size_t i = 0;
+       size_t count_commutative=0;
+       size_t count_noncommutative=0;
+       size_t count_noncommutative_composite=0;
+       for (auto & it : assocseq) {
+               rettypes[i] = it.return_type();
+               switch (rettypes[i]) {
                case return_types::commutative:
                        count_commutative++;
                        break;
@@ -355,7 +340,7 @@ ex ncmul::eval(int level) const
                default:
                        throw(std::logic_error("ncmul::eval(): invalid return type"));
                }
-               ++i; ++cit;
+               ++i;
        }
        GINAC_ASSERT(count_commutative+count_noncommutative+count_noncommutative_composite==assocseq.size());
 
@@ -366,15 +351,15 @@ ex ncmul::eval(int level) const
                commutativeseq.reserve(count_commutative+1);
                exvector noncommutativeseq;
                noncommutativeseq.reserve(assocseq.size()-count_commutative);
-               unsigned num = assocseq.size();
-               for (unsigned i=0; i<num; ++i) {
+               size_t num = assocseq.size();
+               for (size_t i=0; i<num; ++i) {
                        if (rettypes[i]==return_types::commutative)
                                commutativeseq.push_back(assocseq[i]);
                        else
                                noncommutativeseq.push_back(assocseq[i]);
                }
-               commutativeseq.push_back((new ncmul(noncommutativeseq,1))->setflag(status_flags::dynallocated));
-               return (new mul(commutativeseq))->setflag(status_flags::dynallocated);
+               commutativeseq.push_back(dynallocate<ncmul>(std::move(noncommutativeseq)));
+               return dynallocate<mul>(std::move(commutativeseq));
        }
                
        // ncmul(x1,y1,x2,y2) -> *(ncmul(x1,x2),ncmul(y1,y2))
@@ -385,20 +370,19 @@ ex ncmul::eval(int level) const
                // elements in assocseq
                GINAC_ASSERT(count_commutative==0);
 
-               unsigned assoc_num = assocseq.size();
+               size_t assoc_num = assocseq.size();
                exvectorvector evv;
-               unsignedvector rttinfos;
+               std::vector<return_type_t> rttinfos;
                evv.reserve(assoc_num);
                rttinfos.reserve(assoc_num);
 
-               cit = assocseq.begin(), citend = assocseq.end();
-               while (cit != citend) {
-                       unsigned ti = cit->return_type_tinfo();
-                       unsigned rtt_num = rttinfos.size();
+               for (auto & it : assocseq) {
+                       return_type_t ti = it.return_type_tinfo();
+                       size_t rtt_num = rttinfos.size();
                        // search type in vector of known types
                        for (i=0; i<rtt_num; ++i) {
-                               if (ti == rttinfos[i]) {
-                                       evv[i].push_back(*cit);
+                               if(ti == rttinfos[i]) {
+                                       evv[i].push_back(it);
                                        break;
                                }
                        }
@@ -407,75 +391,99 @@ ex ncmul::eval(int level) const
                                rttinfos.push_back(ti);
                                evv.push_back(exvector());
                                (evv.end()-1)->reserve(assoc_num);
-                               (evv.end()-1)->push_back(*cit);
+                               (evv.end()-1)->push_back(it);
                        }
-                       ++cit;
                }
 
-               unsigned evv_num = evv.size();
+               size_t evv_num = evv.size();
 #ifdef DO_GINAC_ASSERT
                GINAC_ASSERT(evv_num == rttinfos.size());
                GINAC_ASSERT(evv_num > 0);
-               unsigned s=0;
+               size_t s=0;
                for (i=0; i<evv_num; ++i)
                        s += evv[i].size();
                GINAC_ASSERT(s == assoc_num);
 #endif // def DO_GINAC_ASSERT
                
                // if all elements are of same type, simplify the string
-               if (evv_num == 1)
-                       return evv[0][0].simplify_ncmul(evv[0]);
+               if (evv_num == 1) {
+                       return evv[0][0].eval_ncmul(evv[0]);
+               }
                
                exvector splitseq;
                splitseq.reserve(evv_num);
                for (i=0; i<evv_num; ++i)
-                       splitseq.push_back((new ncmul(evv[i]))->setflag(status_flags::dynallocated));
+                       splitseq.push_back(dynallocate<ncmul>(evv[i]));
                
-               return (new mul(splitseq))->setflag(status_flags::dynallocated);
+               return dynallocate<mul>(splitseq);
        }
        
-       return (new ncmul(assocseq))->setflag(status_flags::dynallocated |
-                                                                                 status_flags::evaluated);
+       return dynallocate<ncmul>(assocseq).setflag(status_flags::evaluated);
 }
 
-ex ncmul::evalm(void) const
+ex ncmul::evalm() const
 {
        // Evaluate children first
-       exvector *s = new exvector;
-       s->reserve(seq.size());
-       exvector::const_iterator it = seq.begin(), itend = seq.end();
-       while (it != itend) {
-               s->push_back(it->evalm());
-               it++;
-       }
+       exvector s;
+       s.reserve(seq.size());
+       for (auto & it : seq)
+               s.push_back(it.evalm());
 
        // If there are only matrices, simply multiply them
-       it = s->begin(); itend = s->end();
-       if (is_ex_of_type(*it, matrix)) {
+       auto it = s.begin(), itend = s.end();
+       if (is_a<matrix>(*it)) {
                matrix prod(ex_to<matrix>(*it));
                it++;
                while (it != itend) {
-                       if (!is_ex_of_type(*it, matrix))
+                       if (!is_a<matrix>(*it))
                                goto no_matrix;
                        prod = prod.mul(ex_to<matrix>(*it));
                        it++;
                }
-               delete s;
                return prod;
        }
 
 no_matrix:
-       return (new ncmul(s))->setflag(status_flags::dynallocated);
+       return dynallocate<ncmul>(std::move(s));
+}
+
+ex ncmul::thiscontainer(const exvector & v) const
+{
+       return dynallocate<ncmul>(v);
+}
+
+ex ncmul::thiscontainer(exvector && v) const
+{
+       return dynallocate<ncmul>(std::move(v));
+}
+
+ex ncmul::conjugate() const
+{
+       if (return_type() != return_types::noncommutative) {
+               return exprseq::conjugate();
+       }
+
+       if (!is_clifford_tinfo(return_type_tinfo())) {
+               return exprseq::conjugate();
+       }
+
+       exvector ev;
+       ev.reserve(nops());
+       for (auto i=end(); i!=begin();) {
+               --i;
+               ev.push_back(i->conjugate());
+       }
+       return dynallocate<ncmul>(std::move(ev));
 }
 
-ex ncmul::thisexprseq(const exvector & v) const
+ex ncmul::real_part() const
 {
-       return (new ncmul(v))->setflag(status_flags::dynallocated);
+       return basic::real_part();
 }
 
-ex ncmul::thisexprseq(exvector * vp) const
+ex ncmul::imag_part() const
 {
-       return (new ncmul(vp))->setflag(status_flags::dynallocated);
+       return basic::imag_part();
 }
 
 // protected
@@ -485,19 +493,19 @@ ex ncmul::thisexprseq(exvector * vp) const
  *  @see ex::diff */
 ex ncmul::derivative(const symbol & s) const
 {
-       unsigned num = seq.size();
+       size_t num = seq.size();
        exvector addseq;
        addseq.reserve(num);
        
        // D(a*b*c) = D(a)*b*c + a*D(b)*c + a*b*D(c)
        exvector ncmulseq = seq;
-       for (unsigned i=0; i<num; ++i) {
+       for (size_t i=0; i<num; ++i) {
                ex e = seq[i].diff(s);
                e.swap(ncmulseq[i]);
-               addseq.push_back((new ncmul(ncmulseq))->setflag(status_flags::dynallocated));
+               addseq.push_back(dynallocate<ncmul>(ncmulseq));
                e.swap(ncmulseq[i]);
        }
-       return (new add(addseq))->setflag(status_flags::dynallocated);
+       return dynallocate<add>(addseq);
 }
 
 int ncmul::compare_same_type(const basic & other) const
@@ -505,7 +513,7 @@ int ncmul::compare_same_type(const basic & other) const
        return inherited::compare_same_type(other);
 }
 
-unsigned ncmul::return_type(void) const
+unsigned ncmul::return_type() const
 {
        if (seq.empty())
                return return_types::commutative;
@@ -513,7 +521,7 @@ unsigned ncmul::return_type(void) const
        bool all_commutative = true;
        exvector::const_iterator noncommutative_element; // point to first found nc element
 
-       exvector::const_iterator i = seq.begin(), end = seq.end();
+       auto i = seq.begin(), end = seq.end();
        while (i != end) {
                unsigned rt = i->return_type();
                if (rt == return_types::noncommutative_composite)
@@ -525,33 +533,28 @@ unsigned ncmul::return_type(void) const
                }
                if ((rt == return_types::noncommutative) && (!all_commutative)) {
                        // another nc element found, compare type_infos
-                       if (noncommutative_element->return_type_tinfo() != i->return_type_tinfo()) {
-                               // diffent types -> mul is ncc
-                               return return_types::noncommutative_composite;
-                       }
+                       if(noncommutative_element->return_type_tinfo() != i->return_type_tinfo())
+                                       return return_types::noncommutative_composite;
                }
                ++i;
        }
        // all factors checked
-       GINAC_ASSERT(!all_commutative); // not all factors should commute, because this is a ncmul();
+       GINAC_ASSERT(!all_commutative); // not all factors should commutate, because this is a ncmul();
        return all_commutative ? return_types::commutative : return_types::noncommutative;
 }
-   
-unsigned ncmul::return_type_tinfo(void) const
+
+return_type_t ncmul::return_type_tinfo() const
 {
        if (seq.empty())
-               return tinfo_key;
+               return make_return_type_t<ncmul>();
 
        // return type_info of first noncommutative element
-       exvector::const_iterator i = seq.begin(), end = seq.end();
-       while (i != end) {
-               if (i->return_type() == return_types::noncommutative)
-                       return i->return_type_tinfo();
-               ++i;
-       }
+       for (auto & i : seq)
+               if (i.return_type() == return_types::noncommutative)
+                       return i.return_type_tinfo();
 
        // no noncommutative element found, should not happen
-       return tinfo_key;
+       return make_return_type_t<ncmul>();
 }
 
 //////////
@@ -566,17 +569,35 @@ unsigned ncmul::return_type_tinfo(void) const
 
 exvector ncmul::expandchildren(unsigned options) const
 {
-       exvector s;
-       s.reserve(seq.size());
-       exvector::const_iterator it = seq.begin(), itend = seq.end();
-       while (it != itend) {
-               s.push_back(it->expand(options));
-               it++;
+       auto cit = this->seq.begin(), end = this->seq.end();
+       while (cit != end) {
+               const ex & expanded_ex = cit->expand(options);
+               if (!are_ex_trivially_equal(*cit, expanded_ex)) {
+
+                       // copy first part of seq which hasn't changed
+                       exvector s(this->seq.begin(), cit);
+                       s.reserve(this->seq.size());
+
+                       // insert changed element
+                       s.push_back(expanded_ex);
+                       ++cit;
+
+                       // copy rest
+                       while (cit != end) {
+                               s.push_back(cit->expand(options));
+                               ++cit;
+                       }
+
+                       return s;
+               }
+
+               ++cit;
        }
-       return s;
+
+       return exvector(); // nothing has changed
 }
 
-const exvector & ncmul::get_factors(void) const
+const exvector & ncmul::get_factors() const
 {
        return seq;
 }
@@ -585,20 +606,21 @@ const exvector & ncmul::get_factors(void) const
 // friend functions
 //////////
 
-ex nonsimplified_ncmul(const exvector & v)
+ex reeval_ncmul(const exvector & v)
 {
-       return (new ncmul(v))->setflag(status_flags::dynallocated);
+       return dynallocate<ncmul>(v);
 }
 
-ex simplified_ncmul(const exvector & v)
+ex hold_ncmul(const exvector & v)
 {
        if (v.empty())
                return _ex1;
        else if (v.size() == 1)
                return v[0];
        else
-               return (new ncmul(v))->setflag(status_flags::dynallocated |
-                                              status_flags::evaluated);
+               return dynallocate<ncmul>(v).setflag(status_flags::evaluated);
 }
 
+GINAC_BIND_UNARCHIVER(ncmul);
+
 } // namespace GiNaC