quit builtin function has been added

src/main/java/serene/simple/RootScope.java

@@ -1,15 +1,15 @@
 package serene.simple;
 
 import java.util.HashMap;
-import java.util.Map;
-
-import serene.simple.builtin.AFn;
 import serene.simple.builtin.PrintlnFn;
+import serene.simple.builtin.QuitFn;
+
 
 public class RootScope extends BaseScope {
   private final BaseScope parent;
   private final HashMap<String, Object> symbolsMapping = new HashMap<String, Object>() {{
       put("println", new PrintlnFn());
+      put("quit", new QuitFn());
     }};
     // "+", PlusFn,
     // "-", MinusFn,

src/main/java/serene/simple/builtin/QuitFn.java

@@ -0,0 +1,15 @@
+package serene.simple.builtin;
+
+import serene.simple.BaseScope;
+
+
+public class QuitFn extends AFn {
+  public String fnName() {
+    return "println";
+  };
+
+  public Object eval(BaseScope scope) {
+      System.exit(0);
+      return null;
+  }
+}