diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5d28cdb82..5039626e2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -22,6 +22,7 @@ add_library(
   src/Parser.cc
   src/Types.cc
   src/Checker.cc
+  src/Evaluator.cc
 )
 target_link_directories(
   BoltCore
diff --git a/include/bolt/Common.hpp b/include/bolt/Common.hpp
index 2b247ef5d..158635610 100644
--- a/include/bolt/Common.hpp
+++ b/include/bolt/Common.hpp
@@ -25,6 +25,11 @@ namespace bolt {
       return Flags & ConfigFlags_TypeVarsRequireForall;
     }
 
+    bool hasImmediateDiagnostics() const noexcept {
+      // TODO make this a configuration flag
+      return true;
+    }
+
   };
 
 }
diff --git a/src/main.cc b/src/main.cc
index d0368e7b8..4664dd5cd 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -13,6 +13,7 @@
 #include "bolt/Scanner.hpp"
 #include "bolt/Parser.hpp"
 #include "bolt/Checker.hpp"
+#include "bolt/Evaluator.hpp"
 
 using namespace bolt;
 
@@ -56,7 +57,7 @@ int main(int argc, const char* argv[]) {
   SF->setParents();
 
   DiagnosticStore DS;
-  Checker TheChecker { Config, DS };
+  Checker TheChecker { Config, DE }; // TODO set this to DS in production
   TheChecker.check(SF);
 
   auto LT = [](const Diagnostic* L, const Diagnostic* R) {
@@ -79,6 +80,19 @@ int main(int argc, const char* argv[]) {
     DE.printDiagnostic(*D);
   }
 
+  if (DE.hasError()) {
+    return 1;
+  }
+
+  Evaluator E;
+  Env TheEnv;
+  TheEnv.add("print", Value::binding([](auto Args) {
+    ZEN_ASSERT(Args.size() == 1)
+    std::cerr << Args[0].asString() << "\n";
+    return Value::unit();
+  }));
+  E.evaluate(SF, TheEnv);
+
   return 0;
 }