new plotter

core/src/main/java/org/solovyev/android/calculator/CalculatorEventType.java

@@ -162,6 +162,9 @@ public enum CalculatorEventType {
     //org.solovyev.android.calculator.plot.PlotInput
     plot_graph,
 
+
+    plot_graph_3d,
+
     //String
     show_evaluation_error;
 

core/src/main/java/org/solovyev/android/calculator/CalculatorUtils.java

@@ -44,9 +44,9 @@ public final class CalculatorUtils {
     public static boolean isPlotPossible(@NotNull Generic expression, @NotNull JsclOperation operation) {
         boolean result = false;
 
-        if (operation == JsclOperation.simplify) {
+        if (operation == JsclOperation.simplify || operation == JsclOperation.numeric) {
             int size = getNotSystemConstants(expression).size();
-            if (size == 1 || size == 2) {
+            if (size == 0 || size == 1 || size == 2) {
                 result = true;
             }
         }