pseries::expand(): do not generate zero terms.

[ginac.git] / ginac / pseries.cpp

diff --git a/ginac/pseries.cpp b/ginac/pseries.cpp
index 2d873a2626c5eae2591b5549a56caa82aca3ac45..409947f473cad7cb41515979fb1dd76fd4800f95 100644 (file)
--- a/ginac/pseries.cpp
+++ b/ginac/pseries.cpp
@@ -136,10 +136,11 @@ void pseries::print(std::ostream &os, unsigned upper_precedence) const
 {
        debugmsg("pseries print", LOGLEVEL_PRINT);
        if (precedence<=upper_precedence) os << "(";
+       // objects of type pseries must not have any zero entries, so the
+       // trivial (zero) pseries needs a special treatment here:
+       if (seq.size()==0)
+               os << '0';
        for (epvector::const_iterator i=seq.begin(); i!=seq.end(); ++i) {
-               // omit zero terms
-               if (i->rest.is_zero())
-                       continue;
                // print a sign, if needed
                if (i!=seq.begin())
                        os << '+';
@@ -177,9 +178,8 @@ void pseries::printraw(std::ostream &os) const
 {
        debugmsg("pseries printraw", LOGLEVEL_PRINT);
        os << "pseries(" << var << ";" << point << ";";
-       for (epvector::const_iterator i=seq.begin(); i!=seq.end(); ++i) {
+       for (epvector::const_iterator i=seq.begin(); i!=seq.end(); ++i)
                os << "(" << (*i).rest << "," << (*i).coeff << "),";
-       }
        os << ")";
 }
 
@@ -302,6 +302,13 @@ int pseries::ldegree(const symbol &s) const
        }
 }
 
+/** Return coefficient of degree n in power series if s is the expansion
+ *  variable.  If the expansion point is nonzero, by definition the n=1
+ *  coefficient in s of a+b*(s-z)+c*(s-z)^2+Order((s-z)^3) is b (assuming
+ *  the expansion took place in the s in the first place).
+ *  If s is not the expansion variable, an attempt is made to convert the
+ *  series to a polynomial and return the corresponding coefficient from
+ *  there. */
 ex pseries::coeff(const symbol &s, int n) const
 {
        if (var.is_equal(s)) {
@@ -333,7 +340,7 @@ ex pseries::coeff(const symbol &s, int n) const
                return convert_to_poly().coeff(s, n);
 }
 
-
+/** Does nothing. */
 ex pseries::collect(const symbol &s) const
 {
        return *this;
@@ -410,8 +417,11 @@ ex pseries::expand(unsigned options) const
 {
        epvector newseq;
        newseq.reserve(seq.size());
-       for (epvector::const_iterator i=seq.begin(); i!=seq.end(); ++i)
-               newseq.push_back(expair(i->rest.expand(), i->coeff));
+       for (epvector::const_iterator i=seq.begin(); i!=seq.end(); ++i) {
+               ex restexp = i->rest.expand();
+               if (!restexp.is_zero())
+                       newseq.push_back(expair(restexp, i->coeff));
+       }
        return (new pseries(relational(var,point), newseq))
                ->setflag(status_flags::dynallocated | status_flags::expanded);
 }