]> www.ginac.de Git - ginac.git/blobdiff - ginac/clifford.cpp
* Now two different simplification paths in clifford::contract_with().
[ginac.git] / ginac / clifford.cpp
index 99c5a65dc355ee81b9eff995539a9f25f89b9636..610073899543b4256769bcf50d401d693e5987db 100644 (file)
@@ -20,6 +20,8 @@
  *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  */
 
+#include <stdexcept>
+
 #include "clifford.h"
 
 #include "ex.h"
@@ -78,7 +80,7 @@ static ex default_metric()
        return m;
 }
 
-clifford::clifford() : representation_label(0), metric(default_metric())
+clifford::clifford() : representation_label(0), metric(default_metric()), anticommuting(false)
 {
        tinfo_key = TINFO_clifford;
 }
@@ -97,7 +99,7 @@ DEFAULT_CTOR(diracgammaR)
 /** Construct object without any indices. This constructor is for internal
  *  use only. Use the dirac_ONE() function instead.
  *  @see dirac_ONE */
-clifford::clifford(const ex & b, unsigned char rl) : inherited(b), representation_label(rl), metric(0)
+clifford::clifford(const ex & b, unsigned char rl, bool anticommut) : inherited(b), representation_label(rl), metric(0), anticommuting(anticommut)
 {
        tinfo_key = TINFO_clifford;
 }
@@ -106,18 +108,18 @@ clifford::clifford(const ex & b, unsigned char rl) : inherited(b), representatio
  *  use only. Use the clifford_unit() or dirac_gamma() functions instead.
  *  @see clifford_unit
  *  @see dirac_gamma */
-clifford::clifford(const ex & b, const ex & mu, const ex & metr, unsigned char rl) : inherited(b, mu), representation_label(rl), metric(metr)
+clifford::clifford(const ex & b, const ex & mu, const ex & metr, unsigned char rl, bool anticommut) : inherited(b, mu), representation_label(rl), metric(metr), anticommuting(anticommut)
 {
        GINAC_ASSERT(is_a<varidx>(mu));
        tinfo_key = TINFO_clifford;
 }
 
-clifford::clifford(unsigned char rl, const ex & metr, const exvector & v, bool discardable) : inherited(not_symmetric(), v, discardable), representation_label(rl), metric(metr)
+clifford::clifford(unsigned char rl, const ex & metr, bool anticommut, const exvector & v, bool discardable) : inherited(not_symmetric(), v, discardable), representation_label(rl), metric(metr), anticommuting(anticommut)
 {
        tinfo_key = TINFO_clifford;
 }
 
-clifford::clifford(unsigned char rl, const ex & metr, std::auto_ptr<exvector> vp) : inherited(not_symmetric(), vp), representation_label(rl), metric(metr)
+clifford::clifford(unsigned char rl, const ex & metr, bool anticommut, std::auto_ptr<exvector> vp) : inherited(not_symmetric(), vp), representation_label(rl), metric(metr), anticommuting(anticommut)
 {
        tinfo_key = TINFO_clifford;
 }
@@ -132,6 +134,7 @@ clifford::clifford(const archive_node & n, lst & sym_lst) : inherited(n, sym_lst
        n.find_unsigned("label", rl);
        representation_label = rl;
        n.find_ex("metric", metric, sym_lst);
+       n.find_bool("anticommuting", anticommuting);
 }
 
 void clifford::archive(archive_node & n) const
@@ -139,6 +142,7 @@ void clifford::archive(archive_node & n) const
        inherited::archive(n);
        n.add_unsigned("label", representation_label);
        n.add_ex("metric", metric);
+       n.add_bool("anticommuting", anticommuting);
 }
 
 DEFAULT_UNARCHIVE(clifford)
@@ -153,15 +157,29 @@ DEFAULT_ARCHIVING(diracgammaR)
 // functions overriding virtual functions from base classes
 //////////
 
-ex clifford::get_metric(const ex & i, const ex & j) const
+ex clifford::get_metric(const ex & i, const ex & j, bool symmetrised) const
 {
-       return indexed(metric, symmetric2(), i, j);
+       if (is_a<indexed>(metric)) {
+               if (symmetrised && !(ex_to<symmetry>(ex_to<indexed>(metric).get_symmetry()).has_symmetry())) {
+                       if (is_a<matrix>(metric.op(0))) {
+                               return indexed((ex_to<matrix>(metric.op(0)).add(ex_to<matrix>(metric.op(0)).transpose())).mul(numeric(1,2)),
+                                              symmetric2(), i, j);
+                       } else {
+                               return simplify_indexed(indexed(metric.op(0)*_ex1_2, i, j) + indexed(metric.op(0)*_ex1_2, j, i));
+                       }
+               } else {
+                       return indexed(metric.op(0), ex_to<symmetry>(ex_to<indexed>(metric).get_symmetry()), i, j);
+               }
+       } else {
+               // should not really happen since all constructors but clifford() make the metric an indexed object
+               return indexed(metric, i, j);
+       }
 }
 
 bool clifford::same_metric(const ex & other) const
 {
        if (is_a<clifford>(other)) {
-               return get_metric().is_equal(ex_to<clifford>(other).get_metric());
+               return same_metric(ex_to<clifford>(other).get_metric());
        } else if (is_a<indexed>(other)) {
                return get_metric(other.op(1), other.op(2)).is_equal(other);
        } else
@@ -375,15 +393,16 @@ bool diracgamma::contract_with(exvector::iterator self, exvector::iterator other
  *  used in cliffordunit::contract_with(). */
 static int find_same_metric(exvector & v, ex & c)
 {
-       for (int i=0; i<v.size();i++) {
-               if (!is_a<clifford>(v[i]) && is_a<indexed>(v[i])
-                   && ex_to<clifford>(c).same_metric(v[i]) 
-                   && (ex_to<varidx>(c.op(1)) == ex_to<indexed>(v[i]).get_indices()[0]
-                       || ex_to<varidx>(c.op(1)).toggle_variance() == ex_to<indexed>(v[i]).get_indices()[0])) {
-                       return ++i; // next to found
+       for (size_t i=0; i<v.size(); i++) {
+               if (is_a<indexed>(v[i]) && !is_a<clifford>(v[i])
+                   && ((ex_to<varidx>(c.op(1)) == ex_to<indexed>(v[i]).get_indices()[0]
+                   && ex_to<varidx>(c.op(1)) == ex_to<indexed>(v[i]).get_indices()[1])
+                   || (ex_to<varidx>(c.op(1)).toggle_variance() == ex_to<indexed>(v[i]).get_indices()[0]
+                   && ex_to<varidx>(c.op(1)).toggle_variance() == ex_to<indexed>(v[i]).get_indices()[1]))) {
+                       return i; // the index of the found
                }
        }
-       return 0; //nothing found
+       return -1; //nothing found
 }
 
 /** Contraction of a Clifford unit with something else. */
@@ -403,70 +422,88 @@ bool cliffordunit::contract_with(exvector::iterator self, exvector::iterator oth
                        return false;
 
                // Find if a previous contraction produces the square of self
-               int prev_square = find_same_metric(v, self[0]);
-               varidx d((new symbol)->setflag(status_flags::dynallocated), ex_to<idx>(self->op(1)).get_dim());
-               ex squared_metric = unit.get_metric(self->op(1), d) * unit.get_metric(d.toggle_variance(), other->op(1));
+               int prev_square = find_same_metric(v, *self);
+               const varidx d((new symbol)->setflag(status_flags::dynallocated), ex_to<idx>(self->op(1)).get_dim()),
+                       in1((new symbol)->setflag(status_flags::dynallocated), ex_to<idx>(self->op(1)).get_dim()),
+                       in2((new symbol)->setflag(status_flags::dynallocated), ex_to<idx>(self->op(1)).get_dim());
+               ex squared_metric;
+               if (prev_square > -1)
+                       squared_metric = simplify_indexed(indexed(v[prev_square].op(0), in1, d) 
+                                                                                         * unit.get_metric(d.toggle_variance(), in2, true)).op(0);
+
+               exvector::iterator before_other = other - 1;
+               const varidx & mu = ex_to<varidx>(self->op(1));
+               const varidx & mu_toggle = ex_to<varidx>(other->op(1));
+               const varidx & alpha = ex_to<varidx>(before_other->op(1));
 
                // e~mu e.mu = Tr ONE
                if (other - self == 1) {
-                       if (prev_square != 0) {
-                               *self = squared_metric;
-                               v[prev_square-1] = _ex1;
-                       } else
-                               *self = unit.get_metric(self->op(1), other->op(1));
+                       if (prev_square > -1) {
+                               *self = indexed(squared_metric, mu, mu_toggle);
+                               v[prev_square] = _ex1;
+                       } else {
+                               *self = unit.get_metric(mu, mu_toggle, true);
+                       }
                        *other = dirac_ONE(rl);
                        return true;
 
-               // e~mu e~alpha e.mu = (2e~alpha^2-Tr) e~alpha
-               } else if (other - self == 2
-                       && is_a<clifford>(self[1])) {
-
-                       const ex & ia = self[1].op(1);
-                       const ex & ib = self[1].op(1);
-                       if (is_a<tensmetric>(unit.get_metric()))
-                               *self = 2 - unit.get_metric(self->op(1), other->op(1));
-                       else if (prev_square != 0) {
-                               *self = 2-squared_metric;
-                               v[prev_square-1] = _ex1;
-                       } else 
-                               *self = 2*unit.get_metric(ia, ib) - unit.get_metric(self->op(1), other->op(1));
-                       *other = _ex1;
-                       return true;
-
-               // e~mu S e~alpha e.mu = 2 e~alpha^3 S - e~mu S e.mu e~alpha
+               } else if (other - self == 2) {
+                       if (is_a<clifford>(*before_other) && ex_to<clifford>(*before_other).get_representation_label() == rl) {
+                               if (ex_to<clifford>(*self).is_anticommuting()) {
+                                       // e~mu e~alpha e.mu = (2*pow(e~alpha, 2) -Tr(B)) e~alpha
+                                       if (prev_square > -1) {
+                                               *self = 2 * indexed(squared_metric, alpha, alpha)
+                                                       - indexed(squared_metric, mu, mu_toggle);
+                                               v[prev_square] = _ex1;
+                                       } else {
+                                               *self = 2 * unit.get_metric(alpha, alpha, true) - unit.get_metric(mu, mu_toggle, true);
+                                       }
+                                       *other = _ex1;
+                                       return true;
+
+                               } else {
+                                       // e~mu e~alpha e.mu = 2*e~mu B(alpha, mu.toggle_variance())-Tr(B) e~alpha
+                                       *self = 2 * (*self) * unit.get_metric(alpha, mu_toggle, true) - unit.get_metric(mu, mu_toggle, true) * (*before_other);
+                                       *before_other = _ex1;
+                                       *other = _ex1;
+                                       return true;
+                               }
+                       } else {
+                               // e~mu S e.mu = Tr S ONE
+                               *self = unit.get_metric(mu, mu_toggle, true);
+                               *other = dirac_ONE(rl);
+                               return true;
+                       }
+               } else {
+               // e~mu S e~alpha e.mu = 2 e~mu S B(alpha, mu.toggle_variance()) - e~mu S e.mu e~alpha
                // (commutate contracted indices towards each other, simplify_indexed()
                // will re-expand and re-run the simplification)
-               } else {
-                       exvector::iterator it = self + 1, next_to_last = other - 1;
-                       while (it != other) {
-                               if (!is_a<clifford>(*it))
-                                       return false;
-                               ++it;
+                       if (std::find_if(self + 1, other, is_not_a_clifford()) != other) {
+                               return false;
                        }
-
-                       it = self + 1;
-                       ex S = _ex1;
-                       while (it != next_to_last) {
-                               S *= *it;
-                               *it++ = _ex1;
+                       
+                       ex S = ncmul(exvector(self + 1, before_other), true);
+
+                       if (is_a<clifford>(*before_other) && ex_to<clifford>(*before_other).get_representation_label() == rl) {
+                               if (ex_to<clifford>(*self).is_anticommuting()) {
+                                       if (prev_square > -1) {
+                                               *self = 2 * (*before_other) * S * indexed(squared_metric, alpha, alpha)
+                                                       - (*self) * S * (*other) * (*before_other);
+                                       } else {
+                                               *self = 2 * (*before_other) * S * unit.get_metric(alpha, alpha, true) - (*self) * S * (*other) * (*before_other);
+                                       }
+                               } else {
+                                       *self = 2 * (*self) * S * unit.get_metric(alpha, mu_toggle, true) - (*self) * S * (*other) * (*before_other);
+                               }
+                       } else {
+                               // simply commutes
+                               *self = (*self) * S * (*other) * (*before_other);
                        }
-
-                       const ex & ia = next_to_last->op(1);
-                       const ex & ib = next_to_last->op(1);
-                       if (is_a<tensmetric>(unit.get_metric()))
-                               *self = 2 * (*next_to_last) * S - (*self) * S * (*other) * (*next_to_last);
-                       else if (prev_square != 0) {
-                               *self = 2 * (*next_to_last) * S  - (*self) * S * (*other) * (*next_to_last)*unit.get_metric(self->op(1),self->op(1));
-                               v[prev_square-1] = _ex1;
-                       } else 
-                               *self = 2 * (*next_to_last) * S* unit.get_metric(ia,ib) - (*self) * S * (*other) * (*next_to_last);
-                       *next_to_last = _ex1;
-                       *other = _ex1;
+                               
+                       std::fill(self + 1, other + 1, _ex1);
                        return true;
                }
-
-       } 
-
+       }
        return false;
 }
 
@@ -580,7 +617,7 @@ ex clifford::eval_ncmul(const exvector & v) const
                                const ex & ia = a.op(1);
                                const ex & ib = b.op(1);
                                if (ia.is_equal(ib)) { // gamma~alpha gamma~alpha -> g~alpha~alpha
-                                       a = ex_to<clifford>(a).get_metric(ia, ib);
+                                       a = ex_to<clifford>(a).get_metric(ia, ib, true);
                                        b = dirac_ONE(representation_label);
                                        something_changed = true;
                                }
@@ -630,7 +667,7 @@ ex clifford::eval_ncmul(const exvector & v) const
        }
 
        if (s.empty())
-               return clifford(diracone(), representation_label) * sign;
+               return dirac_ONE(representation_label) * sign;
        if (something_changed)
                return reeval_ncmul(s) * sign;
        else
@@ -639,12 +676,12 @@ ex clifford::eval_ncmul(const exvector & v) const
 
 ex clifford::thiscontainer(const exvector & v) const
 {
-       return clifford(representation_label, get_metric(), v);
+       return clifford(representation_label, get_metric(), is_anticommuting(), v);
 }
 
 ex clifford::thiscontainer(std::auto_ptr<exvector> vp) const
 {
-       return clifford(representation_label, get_metric(), vp);
+       return clifford(representation_label, get_metric(), is_anticommuting(), vp);
 }
 
 ex diracgamma5::conjugate() const
@@ -669,22 +706,56 @@ ex diracgammaR::conjugate() const
 ex dirac_ONE(unsigned char rl)
 {
        static ex ONE = (new diracone)->setflag(status_flags::dynallocated);
-       return clifford(ONE, rl);
+       return clifford(ONE, rl, false);
 }
 
-ex clifford_unit(const ex & mu, const ex & metr, unsigned char rl)
+ex clifford_unit(const ex & mu, const ex & metr, unsigned char rl, bool anticommuting)
 {
        static ex unit = (new cliffordunit)->setflag(status_flags::dynallocated);
 
-       if (!is_a<varidx>(mu))
-               throw(std::invalid_argument("index of Clifford unit must be of type varidx"));
+       if (!is_a<idx>(mu))
+               throw(std::invalid_argument("clifford_unit(): index of Clifford unit must be of type idx or varidx"));
 
-       if (is_a<indexed>(metr))
-               return clifford(unit, mu, metr.op(0), rl);
-       else if(is_a<tensmetric>(metr) || is_a<matrix>(metr)) 
-               return clifford(unit, mu, metr, rl);
-       else
-               throw(std::invalid_argument("metric for Clifford unit must be of type indexed, tensormetric or matrix"));
+       if (ex_to<idx>(mu).is_symbolic() && !is_a<varidx>(mu))
+               throw(std::invalid_argument("clifford_unit(): symbolic index of Clifford unit must be of type varidx (not idx)"));
+
+       if (is_a<indexed>(metr)) {
+               exvector indices = ex_to<indexed>(metr).get_indices();
+               if ((indices.size() == 2) && is_a<varidx>(indices[0]) && is_a<varidx>(indices[1])) {
+                       return clifford(unit, mu, metr, rl, anticommuting);
+               } else {
+                       throw(std::invalid_argument("clifford_unit(): metric for Clifford unit must be indexed exactly by two indices of same type as the given index"));
+               }
+       } else if (is_a<tensmetric>(metr)) {
+               static varidx xi((new symbol)->setflag(status_flags::dynallocated), ex_to<varidx>(mu).get_dim()),
+                       chi((new symbol)->setflag(status_flags::dynallocated), ex_to<varidx>(mu).get_dim());
+               return clifford(unit, mu, indexed(metr, xi, chi), rl, anticommuting);
+       } else if (is_a<matrix>(metr)) {
+               matrix M = ex_to<matrix>(metr);
+               unsigned n = M.rows();
+               bool symmetric = true;
+               anticommuting = true;
+
+               static varidx xi((new symbol)->setflag(status_flags::dynallocated), n),
+                       chi((new symbol)->setflag(status_flags::dynallocated), n);
+               if ((n ==  M.cols()) && (n == ex_to<varidx>(mu).get_dim())) {
+                       for (unsigned i = 0; i < n; i++) {
+                               for (unsigned j = i+1; j < n; j++) {
+                                       if (M(i, j) != M(j, i)) {
+                                               symmetric = false;
+                                       }
+                                       if (M(i, j) != -M(j, i)) {
+                                               anticommuting = false;
+                                       }
+                               }
+                       }
+                       return clifford(unit, mu, indexed(metr, symmetric?symmetric2():not_symmetric(), xi, chi), rl, anticommuting);
+               } else {
+                       throw(std::invalid_argument("clifford_unit(): metric for Clifford unit must be a square matrix with the same dimensions as index"));
+               }
+       } else {
+               throw(std::invalid_argument("clifford_unit(): metric for Clifford unit must be of type indexed, tensormetric or matrix"));
+       }
 }
 
 ex dirac_gamma(const ex & mu, unsigned char rl)
@@ -692,9 +763,11 @@ ex dirac_gamma(const ex & mu, unsigned char rl)
        static ex gamma = (new diracgamma)->setflag(status_flags::dynallocated);
 
        if (!is_a<varidx>(mu))
-               throw(std::invalid_argument("index of Dirac gamma must be of type varidx"));
+               throw(std::invalid_argument("dirac_gamma(): index of Dirac gamma must be of type varidx"));
 
-       return clifford(gamma, mu, default_metric(), rl);
+       static varidx xi((new symbol)->setflag(status_flags::dynallocated), ex_to<varidx>(mu).get_dim()),
+               chi((new symbol)->setflag(status_flags::dynallocated), ex_to<varidx>(mu).get_dim());
+       return clifford(gamma, mu, indexed(default_metric(), symmetric2(), xi, chi), rl, true);
 }
 
 ex dirac_gamma5(unsigned char rl)
@@ -984,7 +1057,7 @@ ex canonicalize_clifford(const ex & e_)
                                                ex b1, i1, b2, i2;
                                                base_and_index(it[0], b1, i1);
                                                base_and_index(it[1], b2, i2);
-                                               it[0] = (ex_to<clifford>(save0).get_metric(i1, i2) * b1 * b2).simplify_indexed();
+                                               it[0] = (ex_to<clifford>(save0).get_metric(i1, i2, true) * b1 * b2).simplify_indexed();
                                                it[1] = v.size() == 2 ? _ex2 * dirac_ONE(ex_to<clifford>(it[1]).get_representation_label()) : _ex2;
                                                ex sum = ncmul(v);
                                                it[0] = save1;
@@ -1016,42 +1089,81 @@ ex clifford_prime(const ex & e)
                return e;
 }
 
-ex remove_dirac_ONE(const ex & e,  unsigned char rl)
+ex remove_dirac_ONE(const ex & e, unsigned char rl, unsigned options)
 {
-       pointer_to_map_function_1arg<unsigned char> fcn(remove_dirac_ONE, rl);
-       if (is_a<clifford>(e) && ex_to<clifford>(e).get_representation_label() >= rl) {
-               if (is_a<diracone>(e.op(0)))
+       pointer_to_map_function_2args<unsigned char, unsigned> fcn(remove_dirac_ONE, rl, options | 1);
+       bool need_reevaluation = false;
+       ex e1 = e;
+       if (! (options & 1) )  { // is not a child
+               if (options & 2)
+                       e1 = expand_dummy_sum(e, true);
+               e1 = canonicalize_clifford(e1);
+       }
+       
+       if (is_a<clifford>(e1) && ex_to<clifford>(e1).get_representation_label() >= rl) {
+               if (is_a<diracone>(e1.op(0)))
                        return 1;
+               else 
+                       throw(std::invalid_argument("remove_dirac_ONE(): expression is a non-scalar Clifford number!"));
+       } else if (is_a<add>(e1) || is_a<ncmul>(e1) || is_a<mul>(e1)  
+                          || is_a<matrix>(e1) || is_a<lst>(e1)) {
+               if (options & 3) // is a child or was already expanded
+                       return e1.map(fcn);
                else
-                       throw(std::invalid_argument("Expression is a non-scalar Clifford number!"));
-       } else if (is_a<add>(e) || is_a<ncmul>(e) || is_a<mul>(e)  // || is_a<pseries>(e) || is_a<integral>(e)
-                          || is_a<matrix>(e) || is_a<lst>(e)) {
-               return e.map(fcn);
-       } else if (is_a<power>(e)) {
-               return pow(remove_dirac_ONE(e.op(0)), e.op(1));
-       } else
-               return e;
+                       try {
+                               return e1.map(fcn);
+                       } catch (std::exception &p) {
+                               need_reevaluation = true;
+                       }
+       } else if (is_a<power>(e1)) {
+               if (options & 3) // is a child or was already expanded
+                       return pow(remove_dirac_ONE(e1.op(0), rl, options | 1), e1.op(1));
+               else
+                       try {
+                               return pow(remove_dirac_ONE(e1.op(0), rl, options | 1), e1.op(1));
+                       } catch (std::exception &p) {
+                               need_reevaluation = true;
+                       }
+       } 
+       if (need_reevaluation)
+               return remove_dirac_ONE(e, rl, options | 2);
+       return e1;
 }
 
-ex clifford_norm(const ex & e)
+char clifford_max_label(const ex & e, bool ignore_ONE)
 {
-       return sqrt(remove_dirac_ONE(canonicalize_clifford(e * clifford_bar(e)).simplify_indexed()));
+       if (is_a<clifford>(e))
+               if (ignore_ONE && is_a<diracone>(e.op(0)))
+                       return -1;
+               else
+                       return ex_to<clifford>(e).get_representation_label();
+       else {
+               char rl = -1;
+               for (size_t i=0; i < e.nops(); i++) 
+                       rl = (rl > clifford_max_label(e.op(i), ignore_ONE)) ? rl : clifford_max_label(e.op(i), ignore_ONE);
+               return rl;
+       }
 }
 
+ex clifford_norm(const ex & e)
+{
+       return sqrt(remove_dirac_ONE(e * clifford_bar(e)));
+}
+       
 ex clifford_inverse(const ex & e)
 {
        ex norm = clifford_norm(e);
        if (!norm.is_zero())
                return clifford_bar(e) / pow(norm, 2);
        else 
-               throw(std::invalid_argument("Cannot find inverse of Clifford number with zero norm!"));
+               throw(std::invalid_argument("clifford_inverse(): cannot find inverse of Clifford number with zero norm!"));
 }
 
-ex lst_to_clifford(const ex & v, const ex & mu, const ex & metr, unsigned char rl)
+ex lst_to_clifford(const ex & v, const ex & mu, const ex & metr, unsigned char rl, bool anticommuting)
 {
        if (!ex_to<idx>(mu).is_dim_numeric())
-               throw(std::invalid_argument("Index should have a numeric dimension"));
-       ex e = clifford_unit(mu, metr, rl);
+               throw(std::invalid_argument("lst_to_clifford(): Index should have a numeric dimension"));
+       ex e = clifford_unit(mu, metr, rl, anticommuting);
        return lst_to_clifford(v, e);
 }
 
@@ -1074,20 +1186,20 @@ ex lst_to_clifford(const ex & v, const ex & e) {
                                if (dim == max)
                                        return indexed(v, ex_to<varidx>(mu).toggle_variance()) * e;
                                else
-                                       throw(std::invalid_argument("Dimensions of vector and clifford unit mismatch"));
+                                       throw(std::invalid_argument("lst_to_clifford(): dimensions of vector and clifford unit mismatch"));
                        } else
-                               throw(std::invalid_argument("First argument should be a vector vector"));
+                               throw(std::invalid_argument("lst_to_clifford(): first argument should be a vector vector"));
                } else if (is_a<lst>(v)) {
                        if (dim == ex_to<lst>(v).nops())
                                return indexed(matrix(dim, 1, ex_to<lst>(v)), ex_to<varidx>(mu).toggle_variance()) * e;
                        else
-                               throw(std::invalid_argument("List length and dimension of clifford unit mismatch"));
+                               throw(std::invalid_argument("lst_to_clifford(): list length and dimension of clifford unit mismatch"));
                } else
-                       throw(std::invalid_argument("Cannot construct from anything but list or vector"));
+                       throw(std::invalid_argument("lst_to_clifford(): cannot construct from anything but list or vector"));
        } else
-               throw(std::invalid_argument("The second argument should be a Clifford unit"));
+               throw(std::invalid_argument("lst_to_clifford(): the second argument should be a Clifford unit"));
 }
-
 /** Auxiliary structure to define a function for striping one Clifford unit
  * from vectors. Used in  clifford_to_lst(). */
 static ex get_clifford_comp(const ex & e, const ex & c) 
@@ -1106,7 +1218,7 @@ static ex get_clifford_comp(const ex & e, const ex & c)
                                if (ind > e.nops()) 
                                        ind = j;
                                else 
-                                       throw(std::invalid_argument("Expression is a Clifford multi-vector"));
+                                       throw(std::invalid_argument("get_clifford_comp(): expression is a Clifford multi-vector"));
                if (ind < e.nops()) {
                        ex S = 1;
                        bool same_value_index, found_dummy;
@@ -1131,7 +1243,7 @@ static ex get_clifford_comp(const ex & e, const ex & c)
                                        }
                        return (found_dummy ? S : 0);
                } else
-                       throw(std::invalid_argument("Expression is not a Clifford vector to the given units"));
+                       throw(std::invalid_argument("get_clifford_comp(): expression is not a Clifford vector to the given units"));
        } else if (e.is_zero()) 
                return e;
        else if (is_a<clifford>(e) && ex_to<clifford>(e).same_metric(c))
@@ -1141,7 +1253,7 @@ static ex get_clifford_comp(const ex & e, const ex & c)
                else 
                        return 1;
        else
-               throw(std::invalid_argument("Expression is not usable as a Clifford vector"));
+               throw(std::invalid_argument("get_clifford_comp(): expression is not usable as a Clifford vector"));
 }
 
 
@@ -1150,7 +1262,7 @@ lst clifford_to_lst(const ex & e, const ex & c, bool algebraic)
        GINAC_ASSERT(is_a<clifford>(c));
        varidx mu = ex_to<varidx>(c.op(1));
        if (! mu.is_dim_numeric())
-               throw(std::invalid_argument("Index should have a numeric dimension"));
+               throw(std::invalid_argument("clifford_to_lst(): index should have a numeric dimension"));
        unsigned int D = ex_to<numeric>(mu.get_dim()).to_int();
 
        if (algebraic) // check if algebraic method is applicable
@@ -1159,26 +1271,33 @@ lst clifford_to_lst(const ex & e, const ex & c, bool algebraic)
                                or (not is_a<numeric>(pow(c.subs(mu == i), 2))))
                                algebraic = false;
        lst V; 
-       if (algebraic) 
+       if (algebraic) {
                for (unsigned int i = 0; i < D; i++) 
                        V.append(remove_dirac_ONE(
                                                simplify_indexed(canonicalize_clifford(e * c.subs(mu == i) +  c.subs(mu == i) * e))
                                                / (2*pow(c.subs(mu == i), 2))));
-       else {
+       else {
                ex e1 = canonicalize_clifford(e);
-               for (unsigned int i = 0; i < D; i++) 
-                       V.append(get_clifford_comp(e1, c.subs(c.op(1) == i)));
+               try {
+                       for (unsigned int i = 0; i < D; i++) 
+                               V.append(get_clifford_comp(e1, c.subs(c.op(1) == i)));
+               } catch  (std::exception &p) {
+                       /* Try to expand dummy summations to simplify the expression*/
+                       e1 = canonicalize_clifford(expand_dummy_sum(e1, true));
+                       for (unsigned int i = 0; i < D; i++) 
+                               V.append(get_clifford_comp(e1, c.subs(c.op(1) == i)));
+               }
        }
        return V;
 }
 
 
-ex clifford_moebius_map(const ex & a, const ex & b, const ex & c, const ex & d, const ex & v, const ex & G, unsigned char rl)
+ex clifford_moebius_map(const ex & a, const ex & b, const ex & c, const ex & d, const ex & v, const ex & G, unsigned char rl, bool anticommuting)
 {
        ex x, D, cu;
        
        if (! is_a<matrix>(v) && ! is_a<lst>(v))
-               throw(std::invalid_argument("parameter v should be either vector or list"));
+               throw(std::invalid_argument("clifford_moebius_map(): parameter v should be either vector or list"));
        
        if (is_a<clifford>(G)) {
                cu = G;
@@ -1187,24 +1306,24 @@ ex clifford_moebius_map(const ex & a, const ex & b, const ex & c, const ex & d,
                        D = ex_to<varidx>(G.op(1)).get_dim();
                else if (is_a<matrix>(G)) 
                        D = ex_to<matrix>(G).rows(); 
-               else throw(std::invalid_argument("metric should be an indexed object, matrix, or a Clifford unit"));
+               else throw(std::invalid_argument("clifford_moebius_map(): metric should be an indexed object, matrix, or a Clifford unit"));
                
                varidx mu((new symbol)->setflag(status_flags::dynallocated), D);
-               cu = clifford_unit(mu, G, rl);
+               cu = clifford_unit(mu, G, rl, anticommuting);
        }
-
+       
        x = lst_to_clifford(v, cu); 
        ex e = simplify_indexed(canonicalize_clifford((a * x + b) * clifford_inverse(c * x + d)));
        return clifford_to_lst(e, cu, false);
 }
 
-ex clifford_moebius_map(const ex & M, const ex & v, const ex & G, unsigned char rl)
+ex clifford_moebius_map(const ex & M, const ex & v, const ex & G, unsigned char rl, bool anticommuting)
 {
        if (is_a<matrix>(M)) 
-               return clifford_moebius_map(ex_to<matrix>(M)(0,0), ex_to<matrix>(M)(0,1), 
-                                               ex_to<matrix>(M)(1,0), ex_to<matrix>(M)(1,1), v, G, rl);
+               return clifford_moebius_map(ex_to<matrix>(M)(0,0), ex_to<matrix>(M)(0,1),
+                                           ex_to<matrix>(M)(1,0), ex_to<matrix>(M)(1,1), v, G, rl, anticommuting);
        else
-               throw(std::invalid_argument("parameter M should be a matrix"));
+               throw(std::invalid_argument("clifford_moebius_map(): parameter M should be a matrix"));
 }
 
 } // namespace GiNaC