cda-tum
diff --git a/‎extern/boost/config b/‎extern/boost/config
diff --git a/‎extern/boost/multiprecision b/‎extern/boost/multiprecision
diff --git a/‎extern/googletest b/‎extern/googletest
diff --git a/‎include/Definitions.hpp
+5 b/‎include/Definitions.hpp
+5
@@ -1,5 +1,8 @@
 #pragma once
 
+#include "Expression.hpp"
+#include "Rational.hpp"
+
 #include <stdexcept>
 #include <string>
 
@@ -20,6 +23,8 @@ namespace zx {
     static constexpr double PI =
             3.141592653589793238462643383279502884197169399375105820974L;
 
+    using PiExpression = sym::Expression<double, PiRational>;
+
     class ZXException: public std::invalid_argument {
         std::string msg;