Avoid calling log(1-x) for x=1 in Li_projection.
authorStefan Weinzierl <stefanw@thep.physik.uni-mainz.de>
Sun, 12 Jan 2014 21:58:12 +0000 (21:58 +0000)
committerRichard Kreckel <kreckel@ginac.de>
Sun, 12 Jan 2014 21:58:12 +0000 (21:58 +0000)
ginac/inifcns_nstdsums.cpp

index 5f5949b..7487b31 100644 (file)
@@ -346,7 +346,11 @@ cln::cl_N Li_projection(int n, const cln::cl_N& x, const cln::float_format_t& pr
                } else {
                        // choose the faster algorithm
                        if (cln::abs(cln::realpart(x)) > 0.75) {
-                               return -Li2_do_sum(1-x) - cln::log(x) * cln::log(1-x) + cln::zeta(2);
+                               if ( x == 1 ) {
+                                       return cln::zeta(2);
+                               } else {
+                                       return -Li2_do_sum(1-x) - cln::log(x) * cln::log(1-x) + cln::zeta(2);
+                               }
                        } else {
                                return -Li2_do_sum_Xn(1-x) - cln::log(x) * cln::log(1-x) + cln::zeta(2);
                        }
@@ -368,7 +372,8 @@ cln::cl_N Li_projection(int n, const cln::cl_N& x, const cln::float_format_t& pr
                                return Lin_do_sum_Xn(n, x);
                        }
                } else {
-                       cln::cl_N result = -cln::expt(cln::log(x), n-1) * cln::log(1-x) / cln::factorial(n-1);
+                       cln::cl_N result = 0;
+                       if ( x != 1 ) result = -cln::expt(cln::log(x), n-1) * cln::log(1-x) / cln::factorial(n-1);
                        for (int j=0; j<n-1; j++) {
                                result = result + (S_num(n-j-1, 1, 1) - S_num(1, n-j-1, 1-x))
                                                  * cln::expt(cln::log(x), j) / cln::factorial(j);