Fix pow(+(...),2).expand().

[ginac.git] / ginac / power.cpp

diff --git a/ginac/power.cpp b/ginac/power.cpp
index 6d6f81daa0992073e1c5818fae906ceb5a6b9372..b2460fda8661d234dc8c4b6fb30890c5d1920465 100644 (file)
--- a/ginac/power.cpp
+++ b/ginac/power.cpp
@@ -243,7 +243,8 @@ bool power::info(unsigned inf) const
                case info_flags::positive:
                        return basis.info(info_flags::positive) && exponent.info(info_flags::real);
                case info_flags::nonnegative:
-                       return basis.info(info_flags::real) && exponent.info(info_flags::integer) && exponent.info(info_flags::even);
+                       return (basis.info(info_flags::positive) && exponent.info(info_flags::real)) ||
+                              (basis.info(info_flags::real) && exponent.info(info_flags::integer) && exponent.info(info_flags::even));
                case info_flags::has_indices: {
                        if (flags & status_flags::has_indices)
                                return true;
@@ -799,6 +800,51 @@ ex power::expand(unsigned options) const
                return *this;
        }
 
+       // (x*p)^c -> x^c * p^c, if p>0
+       // makes sense before expanding the basis
+       if (is_exactly_a<mul>(basis) && !basis.info(info_flags::indefinite)) {
+               const mul &m = ex_to<mul>(basis);
+               exvector prodseq;
+               epvector powseq;
+               prodseq.reserve(m.seq.size() + 1);
+               powseq.reserve(m.seq.size() + 1);
+               epvector::const_iterator last = m.seq.end();
+               epvector::const_iterator cit = m.seq.begin();
+               bool possign = true;
+
+               // search for positive/negative factors
+               while (cit!=last) {
+                       ex e=m.recombine_pair_to_ex(*cit);
+                       if (e.info(info_flags::positive))
+                               prodseq.push_back(pow(e, exponent).expand(options));
+                       else if (e.info(info_flags::negative)) {
+                               prodseq.push_back(pow(-e, exponent).expand(options));
+                               possign = !possign;
+                       } else
+                               powseq.push_back(*cit);
+                       ++cit;
+               }
+
+               // take care on the numeric coefficient
+               ex coeff=(possign? _ex1 : _ex_1);
+               if (m.overall_coeff.info(info_flags::positive) && m.overall_coeff != _ex1)
+                       prodseq.push_back(power(m.overall_coeff, exponent));
+               else if (m.overall_coeff.info(info_flags::negative) && m.overall_coeff != _ex_1)
+                       prodseq.push_back(power(-m.overall_coeff, exponent));
+               else
+                       coeff *= m.overall_coeff;
+
+               // If positive/negative factors are found, then extract them.
+               // In either case we set a flag to avoid the second run on a part
+               // which does not have positive/negative terms.
+               if (prodseq.size() > 0) {
+                       ex newbasis = coeff*mul(powseq);
+                       ex_to<basic>(newbasis).setflag(status_flags::purely_indefinite);
+                       return ((new mul(prodseq))->setflag(status_flags::dynallocated)*(new power(newbasis, exponent))->setflag(status_flags::dynallocated).expand(options)).expand(options);
+               } else
+                       ex_to<basic>(basis).setflag(status_flags::purely_indefinite);
+       }
+
        const ex expanded_basis = basis.expand(options);
        const ex expanded_exponent = exponent.expand(options);
        
@@ -986,11 +1032,11 @@ ex power::expand_add_2(const add & a, unsigned options) const
                
                if (c.is_equal(_ex1)) {
                        if (is_exactly_a<mul>(r)) {
-                               sum.push_back(expair(expand_mul(ex_to<mul>(r), *_num2_p, options, true),
-                                                    _ex1));
+                               sum.push_back(a.combine_ex_with_coeff_to_pair(expand_mul(ex_to<mul>(r), *_num2_p, options, true),
+                                                                             _ex1));
                        } else {
-                               sum.push_back(expair((new power(r,_ex2))->setflag(status_flags::dynallocated),
-                                                    _ex1));
+                               sum.push_back(a.combine_ex_with_coeff_to_pair((new power(r,_ex2))->setflag(status_flags::dynallocated),
+                                                                             _ex1));
                        }
                } else {
                        if (is_exactly_a<mul>(r)) {