some more comments and cleanups to mul::expand() and ncmul::expand()

[ginac.git] / ginac / mul.cpp

diff --git a/ginac/mul.cpp b/ginac/mul.cpp
index 2cb358efbfda50ea736fc816511069854a77eccb..92e21b3efa4c427f37e2d949a92185eef1d8aaf4 100644 (file)
--- a/ginac/mul.cpp
+++ b/ginac/mul.cpp
@@ -668,42 +668,39 @@ bool mul::can_make_flat(const expair & p) const
 
 ex mul::expand(unsigned options) const
 {
-       if (options == 0 && (flags & status_flags::expanded))
-               return *this;
-       
-       exvector sub_expanded_seq;
-       
+       // First, expand the children
        epvector * expanded_seqp = expandchildren(options);
-       
-       const epvector & expanded_seq = expanded_seqp==0 ? seq : *expanded_seqp;
-       
+       const epvector & expanded_seq = (expanded_seqp == NULL) ? seq : *expanded_seqp;
+
+       // Now, look for all the factors that are sums and multiply each one out
+       // with the next one that is found while collecting the factors which are
+       // not sums
        int number_of_adds = 0;
+       ex last_expanded = _ex1();
        epvector non_adds;
        non_adds.reserve(expanded_seq.size());
-       epvector::const_iterator cit = expanded_seq.begin();
-       epvector::const_iterator last = expanded_seq.end();
-       ex last_expanded = _ex1();
-       while (cit!=last) {
-               if (is_ex_exactly_of_type((*cit).rest,add) &&
-                       ((*cit).coeff.is_equal(_ex1()))) {
+       epvector::const_iterator cit = expanded_seq.begin(), last = expanded_seq.end();
+       while (cit != last) {
+               if (is_ex_exactly_of_type(cit->rest, add) &&
+                       (cit->coeff.is_equal(_ex1()))) {
                        ++number_of_adds;
-                       if (is_ex_exactly_of_type(last_expanded,add)) {
-                               // expand adds
+                       if (is_ex_exactly_of_type(last_expanded, add)) {
                                const add & add1 = ex_to<add>(last_expanded);
-                               const add & add2 = ex_to<add>((*cit).rest);
+                               const add & add2 = ex_to<add>(cit->rest);
                                int n1 = add1.nops();
                                int n2 = add2.nops();
                                exvector distrseq;
                                distrseq.reserve(n1*n2);
                                for (int i1=0; i1<n1; ++i1) {
                                        for (int i2=0; i2<n2; ++i2) {
-                                               distrseq.push_back(add1.op(i1)*add2.op(i2));
+                                               distrseq.push_back(add1.op(i1) * add2.op(i2));
                                        }
                                }
-                               last_expanded = (new add(distrseq))->setflag(status_flags::dynallocated | (options == 0 ? status_flags::expanded : 0));
+                               last_expanded = (new add(distrseq))->
+                                                setflag(status_flags::dynallocated | (options == 0 ? status_flags::expanded : 0));
                        } else {
                                non_adds.push_back(split_ex_to_pair(last_expanded));
-                               last_expanded = (*cit).rest;
+                               last_expanded = cit->rest;
                        }
                } else {
                        non_adds.push_back(*cit);
@@ -713,7 +710,9 @@ ex mul::expand(unsigned options) const
        if (expanded_seqp)
                delete expanded_seqp;
 
-       if (is_ex_exactly_of_type(last_expanded,add)) {
+       // Now the only remaining thing to do is to multiply the factors which
+       // were not sums into the "last_expanded" sum
+       if (is_ex_exactly_of_type(last_expanded, add)) {
                add const & finaladd = ex_to<add>(last_expanded);
                exvector distrseq;
                int n = finaladd.nops();
@@ -721,7 +720,8 @@ ex mul::expand(unsigned options) const
                for (int i=0; i<n; ++i) {
                        epvector factors = non_adds;
                        factors.push_back(split_ex_to_pair(finaladd.op(i)));
-                       distrseq.push_back((new mul(factors,overall_coeff))->setflag(status_flags::dynallocated | (options == 0 ? status_flags::expanded : 0)));
+                       distrseq.push_back((new mul(factors, overall_coeff))->
+                                           setflag(status_flags::dynallocated | (options == 0 ? status_flags::expanded : 0)));
                }
                return ((new add(distrseq))->
                        setflag(status_flags::dynallocated | (options == 0 ? status_flags::expanded : 0)));