[bugfix] ex::is_polynomial(x): fix miscomputations

The function power::is_polynomial(x) sometimes returned false,
even if x did not occur in the power object.

Thanks to Rubel Zilibowitz for reporting this bug.

Similarly, mul::is_polynomial(x) sometimes returned true, even
if x occurred only in the denominator of a rational function.

The function mul::is_polynomial(x) does a simpler version of
power::is_polynomial(x) on its factors. (It's simpler because the
exponents cannot be functions of x.)

diff --git a/check/exam_paranoia.cpp b/check/exam_paranoia.cpp
index 52d261c8b46712962084e373de2de19ae28603c2..2817d18e6c14aa8ce6b3a803f2c92e0717088571 100644 (file)
--- a/check/exam_paranoia.cpp
+++ b/check/exam_paranoia.cpp
@@ -494,11 +494,11 @@ static unsigned exam_paranoia19()
        return 0;
 }
 
        return 0;
 }
 

-// Bug in expairseq::is_polynomial (fixed 2011-05-20).
+// Bugs in is_polynomial (fixed 2011-05-20 and 2014-07-26).

 static unsigned exam_paranoia20()
 {
        unsigned result = 0;
 static unsigned exam_paranoia20()
 {
        unsigned result = 0;

-       symbol x("x");
+       symbol x("x"), y("y");

        ex e1 = sqrt(x*x+1)*sqrt(x+1);
        if (e1.is_polynomial(x)) {
                clog << "sqrt(x*x+1)*sqrt(x+1) is wrongly reported to be a polynomial in x\n";
        ex e1 = sqrt(x*x+1)*sqrt(x+1);
        if (e1.is_polynomial(x)) {
                clog << "sqrt(x*x+1)*sqrt(x+1) is wrongly reported to be a polynomial in x\n";


@@ -509,6 +509,16 @@ static unsigned exam_paranoia20()
                clog << "sqrt(Pi)*x is wrongly reported to be no polynomial in x\n";
                ++result;
        }
                clog << "sqrt(Pi)*x is wrongly reported to be no polynomial in x\n";
                ++result;
        }

+       ex e3 = sqrt(x);
+       if (!e3.is_polynomial(y)) {
+               clog << "sqrt(x) is wrongly reported to be no polynomial in y\n";
+               ++result;
+       }
+       ex e4 = (1+y)/(2+x);
+       if (e4.is_polynomial(x)) {
+               clog << "(1+y)/(2+x) is wrongly reported to be a polynomial in x\n";
+               ++result;
+       }

        return result;
 }
 
        return result;
 }
 

diff --git a/ginac/mul.cpp b/ginac/mul.cpp
index 64660a288a211695a0e91f07f0f2e92b055fe706..73d7b2408afa9dbe996e3c993ca6cdd83f8db600 100644 (file)
--- a/ginac/mul.cpp
+++ b/ginac/mul.cpp
@@ -406,7 +406,7 @@ bool mul::is_polynomial(const ex & var) const
 {
        for (epvector::const_iterator i=seq.begin(); i!=seq.end(); ++i) {
                if (!i->rest.is_polynomial(var) ||
 {
        for (epvector::const_iterator i=seq.begin(); i!=seq.end(); ++i) {
                if (!i->rest.is_polynomial(var) ||

-                   (i->rest.has(var) && !i->coeff.info(info_flags::integer))) {
+                   (i->rest.has(var) && !i->coeff.info(info_flags::nonnegint))) {

                        return false;
                }
        }
                        return false;
                }
        }

diff --git a/ginac/power.cpp b/ginac/power.cpp
index 87792b922099215e6b00b9744724eef7ca481ab6..1bd122b8767c6a31c1dedcdf09689425ff2b7021 100644 (file)
--- a/ginac/power.cpp
+++ b/ginac/power.cpp
@@ -289,11 +289,16 @@ ex power::map(map_function & f) const
 
 bool power::is_polynomial(const ex & var) const
 {
 
 bool power::is_polynomial(const ex & var) const
 {

-       if (exponent.has(var))
-               return false;
-       if (!exponent.info(info_flags::nonnegint))
-               return false;
-       return basis.is_polynomial(var);
+       if (basis.is_polynomial(var)) {
+               if (basis.has(var))
+                       // basis is non-constant polynomial in var
+                       return exponent.info(info_flags::nonnegint);
+               else
+                       // basis is constant in var
+                       return !exponent.has(var);
+       }
+       // basis is a non-polynomial function of var
+       return false;

 }
 
 int power::degree(const ex & s) const
 }
 
 int power::degree(const ex & s) const