[GiNaC-list] simple patch for Li_evalf

[Sheplyakov Alexei]

Hello!

This short program

#include <iostream>
#include <ginac/ginac.h>
using namespace std;
using namespace GiNaC;

int main(int argc, char** argv)
{
	ex test = Li(5, exp(I*Pi/3));
	cout << test << " = " << test.evalf() << endl;
	return 0;
}

gives

Li(5,exp((1/3*I)*Pi)) = Li(5,exp((1/3*I)*Pi))

instead of expected

Li(5,exp((1/3*I)*Pi)) = 0.48005914589970829926+0.89203268884598503196*I

Attached patch seems to solve the problem.

Best regards,
	Alexei.

-------------- next part --------------
diff -Nru GiNaC-1.2.3-orig/ginac/inifcns_nstdsums.cpp GiNaC-1.2.3/ginac/inifcns_nstdsums.cpp
--- GiNaC-1.2.3-orig/ginac/inifcns_nstdsums.cpp	2004-09-23 10:55:05.000000000 +0400
+++ GiNaC-1.2.3/ginac/inifcns_nstdsums.cpp	2004-09-23 11:14:09.000000000 +0400
@@ -504,8 +504,13 @@
 static ex Li_evalf(const ex& x1, const ex& x2)
 {
 	// classical polylogs
-	if (is_a<numeric>(x1) && is_a<numeric>(x2)) {
-		return Li_num(ex_to<numeric>(x1).to_int(), ex_to<numeric>(x2));
+	if (is_a<numeric>(x1) && !is_a<lst>(x2)) {
+		// try to numerically evaluate second argument
+		ex x2_val = x2.evalf();
+		if (is_a<numeric>(x2_val))
+			return Li_num(ex_to<numeric>(x1).to_int(), ex_to<numeric>(x2_val));
+		else
+			return Li(x1,x2).hold();
 	}
 	// multiple polylogs
 	else if (is_a<lst>(x1) && is_a<lst>(x2)) {