Modifying emptyset.h and sexpr. Adding SetLanguage.

- Modifies expr/emptyset.h to use SetType only as an incomplete type within expr/emptyset.h. This breaks the include cycle between expr/emptyset.h, expr/expr.h and expr/type.h.
- Refactors SExpr to avoid a potentially infinite cycle. This is likely overkill, but it works.
- Moving Expr::setlanguage and related utilities out of the Expr class and into their own file. This allows files in util/ to know the output language set on an ostream.

1 files changed, 3 insertions, 2 deletions

diff --git a/examples/api/strings.cpp b/examples/api/strings.cpp
index 14ab0e64d..2e5d467d3 100644
--- a/examples/api/strings.cpp
+++ b/examples/api/strings.cpp
@@ -18,6 +18,7 @@
 
 //#include <cvc4/cvc4.h> // use this after CVC4 is properly installed
 #include "smt/smt_engine.h"
+#include "options/set_language.h"
 
 using namespace CVC4;
 
@@ -35,8 +36,8 @@ int main() {
   smt.setOption("strings-exp", true);
 
   // Set output language to SMTLIB2
-  std::cout << Expr::setlanguage(language::output::LANG_SMTLIB_V2);
-  
+  std::cout << language::SetLanguage(language::output::LANG_SMTLIB_V2);
+
   // String type
   Type string = em.stringType();