Dear All, Consider the following program: #include <ginac/ginac.h> #include <fstream> using namespace std; using namespace GiNaC; int main(){ realsymbol a("a"); varidx mu(symbol("mu", "\\mu"), 1); ex e = clifford_unit(mu, diag_matrix(lst(-1))), e0=e.subs(mu==0); cout << e0*e0*exp(a*e0) << endl; // -> exp(e0*a) cout << exp(a*e0)*e0*e0 << endl; // -> exp(e0*a)*e0*e0 } The expression in the second output is not simplified for the following reason. When the method ncmul::eval() collects non-commuting terms, the function exp(e0*a) gets the type of its first noncommuting argument, i.e. e0 (this is defined by function::return_type()). So all three factors are of the same type. However, later on, when ncmul::eval() calls the method eval_ncmul() for the first term in the product, e.i. exp(e0*a), it falls back to basic::eval_ncmul() not clifford::eval_ncmul() as one may expect. I am providing below a small patch which makes the behaviour of class function more consistent in this respect. Best wishes, Vladimir -- Vladimir V. Kisil email: kisilv@maths.leeds.ac.uk -- www: http://maths.leeds.ac.uk/~kisilv/ Parent: 6850c16435de33396ccd505ff26b4d4574fa74cf (Fixed bug in mLi summation causing premature drop-out and made Nielsen polylog) Branch: master Follows: release_1-4-0 Precedes: Method function::eval_ncmul() is defined to match the behaviour of function::return_type() ------------------------------ ginac/function.pl ------------------------------ index e91278c..3b22143 100644 @@ -507,6 +507,7 @@ public: ex expand(unsigned options=0) const; ex eval(int level=0) const; ex evalf(int level=0) const; + ex eval_ncmul(const exvector & v) const; unsigned calchash() const; ex series(const relational & r, int order, unsigned options = 0) const; ex thiscontainer(const exvector & v) const; @@ -1053,6 +1054,16 @@ ${evalf_switch_statement} throw(std::logic_error("function::evalf(): invalid nparams")); } +/* +* This method is defined to be in line with behaviour of function::return_type() +*/ +ex function::eval_ncmul(const exvector & v) const +{ + // If this function is called then the list of arguments is non-empty + // and the first argument is non-commutative, see function::return_type() + return seq.begin()->eval_ncmul(v); +} + unsigned function::calchash() const { unsigned v = golden_ratio_hash(golden_ratio_hash((p_int)tinfo()) ^ serial);