diff --git a/app/src/main/java/org/solovyev/android/calculator/ActivityUi.java b/app/src/main/java/org/solovyev/android/calculator/ActivityUi.java
index cc13194d..292ca93c 100644
--- a/app/src/main/java/org/solovyev/android/calculator/ActivityUi.java
+++ b/app/src/main/java/org/solovyev/android/calculator/ActivityUi.java
@@ -223,14 +223,23 @@ public class ActivityUi extends BaseUi {
                        @Nonnull String tag,
                        @Nonnull Class<? extends Fragment> fragmentClass,
                        @Nullable Bundle fragmentArgs,
-                       int captionResId,
+                       int title,
+                       int parentViewId) {
+        addTab(activity, tag, fragmentClass, fragmentArgs, activity.getString(title), parentViewId);
+    }
+
+    public void addTab(@Nonnull AppCompatActivity activity,
+                       @Nonnull String tag,
+                       @Nonnull Class<? extends Fragment> fragmentClass,
+                       @Nullable Bundle fragmentArgs,
+                       @Nullable CharSequence title,
                        int parentViewId) {
         final ActionBar actionBar = activity.getSupportActionBar();
         Check.isNotNull(actionBar);
 
         final ActionBar.Tab tab = actionBar.newTab();
         tab.setTag(tag);
-        tab.setText(captionResId);
+        tab.setText(title);
 
         final ActionBarFragmentTabListener listener = new ActionBarFragmentTabListener(activity, tag, fragmentClass, fragmentArgs, parentViewId);
         tab.setTabListener(listener);
diff --git a/app/src/main/java/org/solovyev/android/calculator/BaseActivity.java b/app/src/main/java/org/solovyev/android/calculator/BaseActivity.java
index d0e848c5..47b7ef85 100644
--- a/app/src/main/java/org/solovyev/android/calculator/BaseActivity.java
+++ b/app/src/main/java/org/solovyev/android/calculator/BaseActivity.java
@@ -2,11 +2,15 @@ package org.solovyev.android.calculator;
 
 import android.os.Bundle;
 import android.support.annotation.LayoutRes;
+import android.support.v4.app.Fragment;
 import android.support.v7.app.AppCompatActivity;
 import android.view.KeyEvent;
 import android.view.MenuItem;
+import org.solovyev.android.calculator.entities.Category;
+import org.solovyev.android.calculator.entities.BaseEntitiesFragment;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 
 public class BaseActivity extends AppCompatActivity {
 
@@ -92,4 +96,17 @@ public class BaseActivity extends AppCompatActivity {
         }
         return super.onOptionsItemSelected(item);
     }
+
+    protected final void addTab(@Nonnull Category category, @Nonnull CalculatorFragmentType type) {
+        final CharSequence title = getString(category.title());
+        addTab(category, type, title);
+    }
+
+    protected final void addTab(@Nonnull Category category, @Nonnull CalculatorFragmentType type, @Nullable CharSequence title) {
+        final Bundle arguments = new Bundle(1);
+        arguments.putString(BaseEntitiesFragment.ARG_CATEGORY, category.name());
+        final String fragmentTag = type.createSubFragmentTag(category.name());
+        final Class<? extends Fragment> fragmentClass = type.getFragmentClass();
+        ui.addTab(this, fragmentTag, fragmentClass, arguments, title, R.id.main_layout);
+    }
 }
diff --git a/app/src/main/java/org/solovyev/android/calculator/math/edit/BaseEntitiesFragment.java b/app/src/main/java/org/solovyev/android/calculator/entities/BaseEntitiesFragment.java
similarity index 93%
rename from app/src/main/java/org/solovyev/android/calculator/math/edit/BaseEntitiesFragment.java
rename to app/src/main/java/org/solovyev/android/calculator/entities/BaseEntitiesFragment.java
index 8e0f6be7..b9156799 100644
--- a/app/src/main/java/org/solovyev/android/calculator/math/edit/BaseEntitiesFragment.java
+++ b/app/src/main/java/org/solovyev/android/calculator/entities/BaseEntitiesFragment.java
@@ -20,12 +20,11 @@
  * Site:  http://se.solovyev.org
  */
 
-package org.solovyev.android.calculator.math.edit;
+package org.solovyev.android.calculator.entities;
 
 import android.app.Activity;
 import android.content.Context;
 import android.os.Bundle;
-import android.os.Handler;
 import android.support.annotation.NonNull;
 import android.support.v7.widget.LinearLayoutManager;
 import android.support.v7.widget.RecyclerView;
@@ -40,7 +39,6 @@ import org.solovyev.android.Check;
 import org.solovyev.android.calculator.BaseFragment;
 import org.solovyev.android.calculator.CalculatorFragmentType;
 import org.solovyev.android.calculator.R;
-import org.solovyev.android.calculator.entities.Category;
 import org.solovyev.android.views.llm.DividerItemDecoration;
 import org.solovyev.common.math.MathEntity;
 import org.solovyev.common.text.Strings;
@@ -63,8 +61,6 @@ public abstract class BaseEntitiesFragment<E extends MathEntity> extends BaseFra
         }
     };
 
-    @Nonnull
-    private final Handler uiHandler = new Handler();
     @Bind(R.id.entities_fab)
     public FloatingActionButton fab;
     @Bind(R.id.entities_recyclerview)
@@ -150,18 +146,13 @@ public abstract class BaseEntitiesFragment<E extends MathEntity> extends BaseFra
         return adapter;
     }
 
-    @Nonnull
-    protected Handler getUiHandler() {
-        return uiHandler;
-    }
-
     @SuppressWarnings("deprecation")
-    protected final void copyDescription(@Nonnull E entity) {
-        final String description = getDescription(entity);
-        if (!Strings.isEmpty(description)) {
-            final ClipboardManager clipboard = (ClipboardManager) getActivity().getSystemService(Activity.CLIPBOARD_SERVICE);
-            clipboard.setText(description);
+    protected final void copyText(@Nullable String text) {
+        if (!Strings.isEmpty(text)) {
+            return;
         }
+        final ClipboardManager clipboard = (ClipboardManager) getActivity().getSystemService(Activity.CLIPBOARD_SERVICE);
+        clipboard.setText(text);
     }
 
     protected void onEntityAdded(@NonNull E entity) {
@@ -288,11 +279,6 @@ public abstract class BaseEntitiesFragment<E extends MathEntity> extends BaseFra
             list.set(position, entity);
         }
 
-        public void sort() {
-            Collections.sort(list, COMPARATOR);
-            notifyDataSetChanged();
-        }
-
         public void add(@Nonnull E entity) {
             final int itemCount = getItemCount();
             for (int i = 0; i < itemCount; i++) {
diff --git a/app/src/main/java/org/solovyev/android/calculator/functions/FunctionsActivity.java b/app/src/main/java/org/solovyev/android/calculator/functions/FunctionsActivity.java
index 0e1cc0ff..71e335ac 100644
--- a/app/src/main/java/org/solovyev/android/calculator/functions/FunctionsActivity.java
+++ b/app/src/main/java/org/solovyev/android/calculator/functions/FunctionsActivity.java
@@ -23,19 +23,16 @@
 package org.solovyev.android.calculator.functions;
 
 import android.os.Bundle;
-import android.support.v4.app.Fragment;
 import org.solovyev.android.calculator.BaseActivity;
 import org.solovyev.android.calculator.CalculatorFragmentType;
 import org.solovyev.android.calculator.R;
-import org.solovyev.android.calculator.math.edit.FunctionsFragment;
+import org.solovyev.android.calculator.operators.OperatorCategory;
 
-import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 
 public class FunctionsActivity extends BaseActivity {
 
     public static final String EXTRA_FUNCTION = "function";
-    private static final CalculatorFragmentType FRAGMENT_TYPE = CalculatorFragmentType.functions;
 
     public FunctionsActivity() {
         super(R.layout.main_empty, FunctionsActivity.class.getSimpleName());
@@ -46,7 +43,11 @@ public class FunctionsActivity extends BaseActivity {
         super.onCreate(savedInstanceState);
 
         for (FunctionCategory category : FunctionCategory.values()) {
-            addTab(category);
+            addTab(category, CalculatorFragmentType.functions);
+        }
+
+        for (OperatorCategory category : OperatorCategory.values()) {
+            addTab(category, CalculatorFragmentType.operators, getString(R.string.c_operators) + ": " + getString(category.title()));
         }
 
         if (savedInstanceState == null) {
@@ -57,12 +58,4 @@ public class FunctionsActivity extends BaseActivity {
             }
         }
     }
-
-    private void addTab(@Nonnull FunctionCategory category) {
-        final Bundle arguments = new Bundle(1);
-        arguments.putString(FunctionsFragment.ARG_CATEGORY, category.name());
-        final String fragmentTag = FRAGMENT_TYPE.createSubFragmentTag(category.name());
-        final Class<? extends Fragment> fragmentClass = FRAGMENT_TYPE.getFragmentClass();
-        ui.addTab(this, fragmentTag, fragmentClass, arguments, category.title, R.id.main_layout);
-    }
 }
\ No newline at end of file
diff --git a/app/src/main/java/org/solovyev/android/calculator/math/edit/FunctionsFragment.java b/app/src/main/java/org/solovyev/android/calculator/math/edit/FunctionsFragment.java
index 877e15dc..c8329d16 100644
--- a/app/src/main/java/org/solovyev/android/calculator/math/edit/FunctionsFragment.java
+++ b/app/src/main/java/org/solovyev/android/calculator/math/edit/FunctionsFragment.java
@@ -33,6 +33,7 @@ import jscl.math.function.Function;
 import jscl.math.function.IFunction;
 import org.solovyev.android.Check;
 import org.solovyev.android.calculator.*;
+import org.solovyev.android.calculator.entities.BaseEntitiesFragment;
 import org.solovyev.android.calculator.entities.Category;
 import org.solovyev.android.calculator.entities.EntityRemovalDialog;
 import org.solovyev.android.calculator.functions.*;
diff --git a/app/src/main/java/org/solovyev/android/calculator/math/edit/OperatorsActivity.java b/app/src/main/java/org/solovyev/android/calculator/math/edit/OperatorsActivity.java
index 5cca9877..32c17e4d 100644
--- a/app/src/main/java/org/solovyev/android/calculator/math/edit/OperatorsActivity.java
+++ b/app/src/main/java/org/solovyev/android/calculator/math/edit/OperatorsActivity.java
@@ -29,6 +29,7 @@ import org.solovyev.android.calculator.CalculatorEventData;
 import org.solovyev.android.calculator.CalculatorEventListener;
 import org.solovyev.android.calculator.CalculatorEventType;
 import org.solovyev.android.calculator.CalculatorFragmentType;
+import org.solovyev.android.calculator.entities.BaseEntitiesFragment;
 import org.solovyev.android.calculator.operators.OperatorCategory;
 import org.solovyev.android.calculator.R;
 
diff --git a/app/src/main/java/org/solovyev/android/calculator/math/edit/OperatorsFragment.java b/app/src/main/java/org/solovyev/android/calculator/math/edit/OperatorsFragment.java
index f4eda90c..5497d0ee 100644
--- a/app/src/main/java/org/solovyev/android/calculator/math/edit/OperatorsFragment.java
+++ b/app/src/main/java/org/solovyev/android/calculator/math/edit/OperatorsFragment.java
@@ -27,6 +27,7 @@ import android.view.ContextMenu;
 import android.view.MenuItem;
 import jscl.math.operator.Operator;
 import org.solovyev.android.calculator.*;
+import org.solovyev.android.calculator.entities.BaseEntitiesFragment;
 import org.solovyev.android.calculator.entities.Category;
 import org.solovyev.common.text.Strings;
 
diff --git a/app/src/main/java/org/solovyev/android/calculator/operators/OperatorCategory.java b/app/src/main/java/org/solovyev/android/calculator/operators/OperatorCategory.java
index 20c9eb90..e546a883 100644
--- a/app/src/main/java/org/solovyev/android/calculator/operators/OperatorCategory.java
+++ b/app/src/main/java/org/solovyev/android/calculator/operators/OperatorCategory.java
@@ -23,28 +23,14 @@
 package org.solovyev.android.calculator.operators;
 
 import android.support.annotation.StringRes;
-
+import jscl.math.operator.*;
 import org.solovyev.android.calculator.R;
 import org.solovyev.android.calculator.entities.Category;
 
 import javax.annotation.Nonnull;
 
-import jscl.math.operator.Derivative;
-import jscl.math.operator.IndefiniteIntegral;
-import jscl.math.operator.Integral;
-import jscl.math.operator.Operator;
-import jscl.math.operator.Product;
-import jscl.math.operator.Sum;
-
 public enum OperatorCategory implements Category<Operator> {
 
-    my(R.string.c_fun_category_my) {
-        @Override
-        public boolean isInCategory(@Nonnull Operator operator) {
-            return !operator.isSystem();
-        }
-    },
-
     common(R.string.c_fun_category_common) {
         @Override
         public boolean isInCategory(@Nonnull Operator operator) {
diff --git a/app/src/main/java/org/solovyev/android/calculator/variables/VariablesActivity.java b/app/src/main/java/org/solovyev/android/calculator/variables/VariablesActivity.java
index 9c1edd88..66109359 100644
--- a/app/src/main/java/org/solovyev/android/calculator/variables/VariablesActivity.java
+++ b/app/src/main/java/org/solovyev/android/calculator/variables/VariablesActivity.java
@@ -23,18 +23,15 @@
 package org.solovyev.android.calculator.variables;
 
 import android.os.Bundle;
-import android.support.v4.app.Fragment;
 import org.solovyev.android.calculator.BaseActivity;
 import org.solovyev.android.calculator.CalculatorFragmentType;
 import org.solovyev.android.calculator.R;
 
-import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 
 public class VariablesActivity extends BaseActivity {
 
     public static final String EXTRA_VARIABLE = "variable";
-    private static final CalculatorFragmentType FRAGMENT_TYPE = CalculatorFragmentType.variables;
 
     public VariablesActivity() {
         super(R.layout.main_empty, VariablesActivity.class.getSimpleName());
@@ -45,7 +42,7 @@ public class VariablesActivity extends BaseActivity {
         super.onCreate(savedInstanceState);
 
         for (VariableCategory category : VariableCategory.values()) {
-            addTab(category);
+            addTab(category, CalculatorFragmentType.variables);
         }
 
         if (savedInstanceState == null) {
@@ -56,12 +53,4 @@ public class VariablesActivity extends BaseActivity {
             }
         }
     }
-
-    private void addTab(@Nonnull VariableCategory category) {
-        final Bundle arguments = new Bundle(1);
-        arguments.putString(VariablesFragment.ARG_CATEGORY, category.name());
-        final String fragmentTag = FRAGMENT_TYPE.createSubFragmentTag(category.name());
-        final Class<? extends Fragment> fragmentClass = FRAGMENT_TYPE.getFragmentClass();
-        ui.addTab(this, fragmentTag, fragmentClass, arguments, category.title(), R.id.main_layout);
-    }
 }
diff --git a/app/src/main/java/org/solovyev/android/calculator/variables/VariablesFragment.java b/app/src/main/java/org/solovyev/android/calculator/variables/VariablesFragment.java
index 77d9769d..69f63100 100644
--- a/app/src/main/java/org/solovyev/android/calculator/variables/VariablesFragment.java
+++ b/app/src/main/java/org/solovyev/android/calculator/variables/VariablesFragment.java
@@ -35,7 +35,7 @@ import org.solovyev.android.calculator.*;
 import org.solovyev.android.calculator.entities.Category;
 import org.solovyev.android.calculator.entities.EntityRemovalDialog;
 import org.solovyev.android.calculator.math.MathType;
-import org.solovyev.android.calculator.math.edit.BaseEntitiesFragment;
+import org.solovyev.android.calculator.entities.BaseEntitiesFragment;
 import org.solovyev.common.JPredicate;
 import org.solovyev.common.collections.Collections;
 import org.solovyev.common.text.Strings;
@@ -160,10 +160,7 @@ public class VariablesFragment extends BaseEntitiesFragment<IConstant> {
                 });
                 return true;
             case R.string.c_copy_value:
-                final String value = constant.getValue();
-                if (!Strings.isEmpty(value)) {
-                    Locator.getInstance().getClipboard().setText(value);
-                }
+                copyText(constant.getValue());
                 return true;
         }
         return false;
diff --git a/jscl/src/main/java/jscl/text/ParserUtils.java b/jscl/src/main/java/jscl/text/ParserUtils.java
index a5f39710..86b67cc7 100644
--- a/jscl/src/main/java/jscl/text/ParserUtils.java
+++ b/jscl/src/main/java/jscl/text/ParserUtils.java
@@ -1,14 +1,13 @@
 package jscl.text;
 
-import java.lang.reflect.Array;
-import java.util.Collections;
-
-import javax.annotation.Nonnull;
-import javax.annotation.Nullable;
-
 import jscl.math.Generic;
 import jscl.text.msg.Messages;
 
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import java.lang.reflect.Array;
+import java.util.Collections;
+
 /**
  * User: serso
  * Date: 10/27/11
@@ -130,7 +129,7 @@ public class ParserUtils {
     }
 
     public static <T, U> T[] copyOf(U[] array, int newLength, Class<? extends T[]> newType) {
-        T[] copy = (newType == Object[].class)
+        T[] copy = ((Object) newType == (Object) Object[].class)
                 ? (T[]) new Object[newLength]
                 : (T[]) Array.newInstance(newType.getComponentType(), newLength);