From: Alexei Sheplyakov <varg@theor.jinr.ru>
Date: Thu, 6 Nov 2008 14:51:28 +0000 (+0300)
Subject: Fix is_polynomial() so it works as advertised in the manual.
X-Git-Tag: release_1-4-4~3
X-Git-Url: https://www.ginac.de/ginac.git//ginac.git?a=commitdiff_plain;h=398f4eb2273a8a6adfe54361aa98cce12fe70174;p=ginac.git

Fix is_polynomial() so it works as advertised in the manual.

GiNaC manual says:
"Testing whether an expression is a polynomial in one or more variables
can be done with the method

 bool ex::is_polynomial(const ex & vars) const;
In the case of more than one variable, the variables are given as a list.

(x*y*sin(y)).is_polynomial(x)        // Returns true.
(x*y*sin(y)).is_polynomial(lst(x,y)) // Returns false."

However, the implementation is a bit inconsistent, as GiNaC reports
sin(x) + 2*s     is a polynomial in s, but
pow(2,x) + 2*s   is not a polynomial in s.

This patch fixes the inconsistency. Thanks to Jonathan Cross for reporting
this bug.
---

diff --git a/check/Makefile.am b/check/Makefile.am
index a96dcfe7..549532fc 100644
--- a/check/Makefile.am
+++ b/check/Makefile.am
@@ -3,7 +3,8 @@
 CHECKS = check_numeric \
 	 check_inifcns \
 	 check_matrices \
-	 check_lsolve 
+	 check_lsolve \
+	 check_is_polynomial
 
 EXAMS = exam_paranoia \
 	exam_heur_gcd \
@@ -66,6 +67,9 @@ check_matrices_LDADD = ../ginac/libginac.la
 check_lsolve_SOURCES = check_lsolve.cpp genex.cpp
 check_lsolve_LDADD = ../ginac/libginac.la
 
+check_is_polynomial_SOURCES = check_is_polynomial.cpp
+check_is_polynomial_LDADD = ../ginac/libginac.la
+
 exam_paranoia_SOURCES = exam_paranoia.cpp
 exam_paranoia_LDADD = ../ginac/libginac.la
 
diff --git a/check/check_is_polynomial.cpp b/check/check_is_polynomial.cpp
new file mode 100644
index 00000000..a62f0c26
--- /dev/null
+++ b/check/check_is_polynomial.cpp
@@ -0,0 +1,30 @@
+/*
+ * Check for inconsistency in power::is_polynomial
+ */
+#include "ginac.h"
+#include <iostream>
+#include <stdexcept>
+using namespace std;
+using namespace GiNaC;
+
+static void do_test(const ex& e, const ex& s)
+{
+	if (e.is_polynomial(s))
+		return;
+	cerr << "*** Error: is_polynomial() says \"" << e << "\""
+		<< "is not a polynomial in \"" << s << "\"" << endl;
+	throw std::logic_error("bug in is_polynomial()");
+}
+
+int main(int argc, char** argv)
+{
+	cout << "checking for bugs in is_polynomial()... " << flush;
+	symbol x("x"), s("s");
+	ex e = sin(x) + 2*s;
+	ex g = pow(2, x) + 2*s;
+	do_test(e, s);
+	do_test(g, s);
+	cout << " OK, not found." << endl;
+	return 0;
+}
+	
diff --git a/ginac/power.cpp b/ginac/power.cpp
index f92233c3..ca549300 100644
--- a/ginac/power.cpp
+++ b/ginac/power.cpp
@@ -285,6 +285,8 @@ ex power::map(map_function & f) const
 
 bool power::is_polynomial(const ex & var) const
 {
+	if (!(basis.has(var) || exponent.has(var)))
+		return true; // i.e. 2^x is polynomial in s
 	if (exponent.has(var))
 		return false;
 	if (!exponent.info(info_flags::nonnegint))