Hello!
This simple program:
#include <iostream>
#include <ginac/ginac.h>
using namespace std;
using namespace GiNaC;
int main(int argc, char** argv)
{
symbol A("A");
symbol i_sym("i");
idx i(i_sym, 3);
ex test = indexed(A, i)*indexed(A,i);
exprseq free_ind = test.get_free_indices();
cout << "Free indices of expression " << test << ": ";
cout << free_ind << endl;
return 0;
}
gives:
Free indices of expression (A.i)^2: (.i)
but not just an empty sequence, as I expected.
This patch seems to fix the inconsistency:
diff -u -r GiNaC-orig/ginac/indexed.cpp GiNaC/ginac/indexed.cpp
--- GiNaC-orig/ginac/indexed.cpp 2004-06-10 02:19:36.000000000 +0400
+++ GiNaC/ginac/indexed.cpp 2004-07-26 22:31:52.000000000 +0400
@@ -499,10 +499,31 @@
return free_indices;
}
+// checks if index is symbolic and is_exactly_a<idx>
+struct is_a_symb_idx : public std::unary_function<ex, bool> {
+ bool operator()(const ex & e)
+ {
+ return is_exactly_a<idx>(e) && ex_to<idx>(e).is_symbolic();
+ }
+};
+
exvector power::get_free_indices() const
{
- // Return free indices of basis
- return basis.get_free_indices();
+ exvector tmp_inds = basis.get_free_indices();
+
+ if (exponent.info(info_flags::even)) {
+ // if the exponent is an even number, then any "free" index
+ // of base is actually a dummy index, if it
+ // 1) has no variance,
+ // 2) is not a numeric index
+ exvector really_free;
+ remove_copy_if(tmp_inds.begin(), tmp_inds.end(),
+ back_inserter(really_free), is_a_symb_idx());
+ return really_free;
+ } else {
+ return tmp_inds;
+ }
+
}
/** Rename dummy indices in an expression.