cancel common factors in mass(), fix invariante in trivialIID test

src/Dist.cpp

@@ -123,6 +123,11 @@ namespace prodigy {
 
     ex Dist::mass() const {
         ex res{_gf};
+        /* TODO
+         * normal() cancels common factors, this is needed since we are going to substitute stuff to avoid div by 0
+         * encapsulate this somehow because substitution occurs elsewhere too
+         */
+        res = res.normal();
         for (const auto &v : _vars) {
             res = res.subs(v.second == 1);
         }
@@ -310,7 +315,7 @@ namespace prodigy {
             registerAsVar(symbol(x));
         }
         // first marginalize x away in *this
-        ex res = _gf.subs(_vars[x] == 1);
+        ex res = _gf.normal().subs(_vars[x] == 1);
         // ySubs will be gf of y with (single) var replaced by x
         // do this by simply substituting all known vars for x
         // currently, gathering the symbols that actually occur in y is not implemented

test/TestEquivalence.cpp

@@ -223,7 +223,7 @@ TEST(EquivalenceCheck, trivialIID){
     cout << "l0:\t" << l0 << endl;
     l1 = l0.filterGreater("n", "0");
     cout << "l1:\t" << l1 << endl;
-    l2 = l1.updateIid("tmp", Dist {"1/6 * T * (T^5 - 1) / (T - 1)"}, "n");
+    l2 = l1.updateIid("tmp", Dist {"1/6 * T * (T^6 - 1) / (T - 1)"}, "n");
     cout << "l2:\t" << l2 << endl;
     l3 = l2.update("m", "m+tmp");
     cout << "l3:\t" << l3 << endl;