apply trac 31530 patch pynac power::subs

commit 7746fa2 Author: Dave Witte Morris <Dave.Morris@uleth.ca> Date: Wed Mar 24 17:35:16 2021 -0600 trac 31530 patch pynac power::subs
sagemath · Jun 25, 2021 · 4caca2e · 4caca2e
1 parent 80269c5
commit 4caca2e
Showing 1 changed file with 4 additions and 0 deletions.
diff --git a/src/sage/symbolic/ginac/power.cpp b/src/sage/symbolic/ginac/power.cpp
@@ -745,6 +745,10 @@ ex power::subs(const exmap & m, unsigned options) const
         if (!are_ex_trivially_equal(basis, subsed_basis)
 	 || !are_ex_trivially_equal(exponent, subsed_exponent)) {
 		ex p = power(subsed_basis, subsed_exponent);
+		if (!is_exactly_a<power>(p)) {
+		    // trac 30378 and 31530: do not over-substitute
+	        return p;
+	    }
                 ex t = ex_to<power>(p).subs_one_level(m, options);
                 if ((t-*this).is_zero())
                         return p;