From: Richard Kreckel <kreckel@ginac.de>
Date: Fri, 25 Jul 2014 23:11:11 +0000 (+0000)
Subject: [bugfix] ex::is_polynomial(x): fix miscomputations
X-Git-Tag: release_1-6-3~9
X-Git-Url: https://www.ginac.de/ginac.git//ginac.git?p=ginac.git;a=commitdiff_plain;h=92da4c16f5d6edf276be011a08ce04b352945a83

[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 52d261c8..2817d18e 100644
--- a/check/exam_paranoia.cpp
+++ b/check/exam_paranoia.cpp
@@ -494,11 +494,11 @@ static unsigned exam_paranoia19()
 	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;
-	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";
@@ -509,6 +509,16 @@ static unsigned exam_paranoia20()
 		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;
 }
 
diff --git a/ginac/mul.cpp b/ginac/mul.cpp
index 64660a28..73d7b240 100644
--- 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) ||
-		    (i->rest.has(var) && !i->coeff.info(info_flags::integer))) {
+		    (i->rest.has(var) && !i->coeff.info(info_flags::nonnegint))) {
 			return false;
 		}
 	}
diff --git a/ginac/power.cpp b/ginac/power.cpp
index 87792b92..1bd122b8 100644
--- 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
 {
-	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