diff --git a/app/src/main/java/org/solovyev/android/calculator/functions/BaseFunctionFragment.java b/app/src/main/java/org/solovyev/android/calculator/functions/BaseFunctionFragment.java
index 5c23a2e0..3c63e710 100644
--- a/app/src/main/java/org/solovyev/android/calculator/functions/BaseFunctionFragment.java
+++ b/app/src/main/java/org/solovyev/android/calculator/functions/BaseFunctionFragment.java
@@ -22,8 +22,6 @@
 
 package org.solovyev.android.calculator.functions;
 
-import static org.solovyev.android.calculator.functions.CppFunction.NO_ID;
-
 import android.annotation.SuppressLint;
 import android.content.Context;
 import android.content.DialogInterface;
@@ -59,9 +57,6 @@ import org.solovyev.android.calculator.keyboard.FloatingKeyboardWindow;
 import org.solovyev.android.calculator.view.EditTextCompat;
 import org.solovyev.common.math.MathRegistry;
 
-import butterknife.Bind;
-import butterknife.ButterKnife;
-
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashSet;
@@ -72,6 +67,11 @@ import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 import javax.inject.Inject;
 
+import butterknife.Bind;
+import butterknife.ButterKnife;
+
+import static org.solovyev.android.calculator.functions.CppFunction.NO_ID;
+
 public abstract class BaseFunctionFragment extends BaseDialogFragment implements View.OnClickListener, View.OnFocusChangeListener, View.OnKeyListener {
 
     protected static final String ARG_FUNCTION = "function";
@@ -274,12 +274,6 @@ public abstract class BaseFunctionFragment extends BaseDialogFragment implements
     }
 
     protected boolean validateName() {
-        final String name = nameView.getText().toString();
-        if (!Engine.isValidName(name)) {
-            setError(nameLabel, getString(R.string.function_name_is_not_valid));
-            return false;
-        }
-        clearError(nameLabel);
         return true;
     }
 
diff --git a/app/src/main/java/org/solovyev/android/calculator/functions/EditFunctionFragment.java b/app/src/main/java/org/solovyev/android/calculator/functions/EditFunctionFragment.java
index 38dca236..9f1ae9fe 100644
--- a/app/src/main/java/org/solovyev/android/calculator/functions/EditFunctionFragment.java
+++ b/app/src/main/java/org/solovyev/android/calculator/functions/EditFunctionFragment.java
@@ -12,14 +12,15 @@ import android.support.v7.app.AlertDialog;
 import org.solovyev.android.Activities;
 import org.solovyev.android.Check;
 import org.solovyev.android.calculator.App;
+import org.solovyev.android.calculator.Engine;
 import org.solovyev.android.calculator.R;
 import org.solovyev.android.calculator.entities.EntityRemovalDialog;
 
-import jscl.math.function.Function;
-
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 
+import jscl.math.function.Function;
+
 public class EditFunctionFragment extends BaseFunctionFragment {
 
     public EditFunctionFragment() {
@@ -103,10 +104,11 @@ public class EditFunctionFragment extends BaseFunctionFragment {
 
     @Override
     protected boolean validateName() {
-        if (!super.validateName()) {
+        final String name = nameView.getText().toString();
+        if (!Engine.isValidName(name)) {
+            setError(nameLabel, getString(R.string.function_name_is_not_valid));
             return false;
         }
-        final String name = nameView.getText().toString();
         final Function existingFunction = functionsRegistry.get(name);
         if (existingFunction != null) {
             if (!existingFunction.isIdDefined()) {
diff --git a/app/src/main/java/org/solovyev/android/calculator/plot/ExpressionFunction.java b/app/src/main/java/org/solovyev/android/calculator/plot/ExpressionFunction.java
index c1f6ca0c..e4c12a2e 100644
--- a/app/src/main/java/org/solovyev/android/calculator/plot/ExpressionFunction.java
+++ b/app/src/main/java/org/solovyev/android/calculator/plot/ExpressionFunction.java
@@ -1,46 +1,46 @@
 package org.solovyev.android.calculator.plot;
 
+import android.text.TextUtils;
+
 import org.solovyev.android.plotter.Function;
 
-import jscl.math.Expression;
+import javax.annotation.Nonnull;
+
 import jscl.math.Generic;
 import jscl.math.JsclInteger;
 import jscl.math.NumericWrapper;
-import jscl.math.function.Constant;
+import jscl.math.function.CustomFunction;
 import jscl.math.numeric.Complex;
 import jscl.math.numeric.Numeric;
 import jscl.math.numeric.Real;
 
-import javax.annotation.Nonnull;
-import javax.annotation.Nullable;
-
 public class ExpressionFunction extends Function {
-    private static final Complex NaN = Complex.valueOf(Double.NaN, 0d);
-
     @Nonnull
     public final jscl.math.function.Function function;
-    public final Constant xVariable;
-    public final Constant yVariable;
     public final boolean imaginary;
     public final int arity;
+    private final Generic[] parameters;
 
-    public ExpressionFunction(@Nonnull jscl.math.function.Function function, @Nullable Constant x,
-        @Nullable Constant y, boolean imaginary) {
-        super(imaginary ? "Im(" + function.toString() + ")" : function.toString());
+    public ExpressionFunction(@Nonnull jscl.math.function.Function function,
+                              boolean imaginary) {
+        super(makeFunctionName(function, imaginary));
         this.function = function;
-        this.xVariable = x;
-        this.yVariable = y;
         this.imaginary = imaginary;
-        this.arity = countArity(x, y);
+        this.arity = function.getMaxParameters();
+        this.parameters = new Generic[this.arity];
     }
 
-    private static int countArity(@Nullable Constant x, @Nullable Constant y) {
-        if (x != null && y != null) {
-            return 2;
-        } else if (x == null && y == null) {
-            return 0;
+    @Nonnull
+    private static String makeFunctionName(@Nonnull jscl.math.function.Function function, boolean imaginary) {
+        String name = function.getName();
+        if (TextUtils.isEmpty(name)) {
+            if (function instanceof CustomFunction) {
+                name = ((CustomFunction) function).getContent();
+            } else {
+                name = function.toString();
+            }
         }
-        return 1;
+        return imaginary ? "Im(" + name + ")" : name;
     }
 
     @Override
@@ -50,81 +50,53 @@ public class ExpressionFunction extends Function {
 
     @Override
     public float evaluate() {
-        final Complex value = calculate(function);
-        if (imaginary) {
-            return (float) value.imaginaryPart();
+        try {
+            return unwrap(function.numeric());
+        } catch (RuntimeException e) {
+            return Float.NaN;
         }
-        return (float) value.realPart();
     }
 
     @Override
     public float evaluate(float x) {
-        final Complex value = calculate(function, xVariable, x);
-        if (imaginary) {
-            return (float) value.imaginaryPart();
+        try {
+            parameters[0] = new NumericWrapper(Real.valueOf(x));
+            function.setParameters(parameters);
+            return unwrap(function.numeric());
+        } catch (RuntimeException e) {
+            return Float.NaN;
         }
-        return (float) value.realPart();
     }
 
     @Override
     public float evaluate(float x, float y) {
-        final Complex value = calculate(function, xVariable, x, yVariable, y);
-        if (imaginary) {
-            return (float) value.imaginaryPart();
-        }
-        return (float) value.realPart();
-    }
-
-    @Nonnull
-    public static Complex calculate(jscl.math.function.Function function, Constant xVar,
-        float x, Constant yVar, float y) {
-        try {
-            Generic tmp = function.substitute(xVar, Expression.valueOf((double) x));
-            tmp = tmp.substitute(yVar, Expression.valueOf((double) y));
-            return unwrap(tmp.numeric());
-        } catch (RuntimeException e) {
-            return NaN;
-        }
-    }
-
-    @Nonnull
-    public static Complex calculate(jscl.math.function.Function function, Constant xVar,
-        float x) {
-        try {
-            return unwrap(function.substitute(xVar, Expression.valueOf((double) x)).numeric());
-        } catch (RuntimeException e) {
-            return NaN;
-        }
-    }
-
-    @Nonnull
-    public static Complex calculate(jscl.math.function.Function function) {
         try {
+            parameters[0] = new NumericWrapper(Real.valueOf(x));
+            parameters[1] = new NumericWrapper(Real.valueOf(y));
+            function.setParameters(parameters);
             return unwrap(function.numeric());
         } catch (RuntimeException e) {
-            return NaN;
+            return Float.NaN;
         }
     }
 
-    @Nonnull
-    public static Complex unwrap(Generic numeric) {
+    public float unwrap(Generic numeric) {
         if (numeric instanceof JsclInteger) {
-            return Complex.valueOf(((JsclInteger) numeric).intValue(), 0d);
-        } else if (numeric instanceof NumericWrapper) {
-            return unwrap(((NumericWrapper) numeric).content());
-        } else {
-            return NaN;
+            return ((JsclInteger) numeric).intValue();
         }
+        if (numeric instanceof NumericWrapper) {
+            return unwrap(((NumericWrapper) numeric).content());
+        }
+        return Float.NaN;
     }
 
-    @Nonnull
-    public static Complex unwrap(Numeric content) {
+    public float unwrap(Numeric content) {
         if (content instanceof Real) {
-            return Complex.valueOf(((Real) content).doubleValue(), 0d);
-        } else if (content instanceof Complex) {
-            return ((Complex) content);
-        } else {
-            throw new ArithmeticException();
+            return (float) ((Real) content).doubleValue();
         }
+        if (content instanceof Complex) {
+            return (float) (imaginary ? ((Complex) content).imaginaryPart() : ((Complex) content).realPart());
+        }
+        return Float.NaN;
     }
 }
diff --git a/app/src/main/java/org/solovyev/android/calculator/plot/PlotEditFunctionFragment.java b/app/src/main/java/org/solovyev/android/calculator/plot/PlotEditFunctionFragment.java
index 964deaf1..66984f86 100644
--- a/app/src/main/java/org/solovyev/android/calculator/plot/PlotEditFunctionFragment.java
+++ b/app/src/main/java/org/solovyev/android/calculator/plot/PlotEditFunctionFragment.java
@@ -10,8 +10,6 @@ import android.view.View;
 import android.widget.SeekBar;
 import android.widget.TextView;
 
-import com.google.common.base.Strings;
-
 import org.solovyev.android.calculator.App;
 import org.solovyev.android.calculator.AppComponent;
 import org.solovyev.android.calculator.R;
@@ -23,18 +21,18 @@ import org.solovyev.android.plotter.PlotIconView;
 import org.solovyev.android.plotter.Plotter;
 import org.solovyev.android.plotter.meshes.MeshSpec;
 
-import butterknife.Bind;
-import jscl.math.function.Constant;
-import jscl.math.function.CustomFunction;
-import uz.shift.colorpicker.LineColorPicker;
-import uz.shift.colorpicker.OnColorChangedListener;
-
 import java.util.ArrayList;
 import java.util.List;
 
 import javax.annotation.Nonnull;
 import javax.inject.Inject;
 
+import butterknife.Bind;
+import jscl.math.function.Constant;
+import jscl.math.function.CustomFunction;
+import uz.shift.colorpicker.LineColorPicker;
+import uz.shift.colorpicker.OnColorChangedListener;
+
 public class PlotEditFunctionFragment extends BaseFunctionFragment
     implements SeekBar.OnSeekBarChangeListener {
     @Inject
@@ -67,22 +65,14 @@ public class PlotEditFunctionFragment extends BaseFunctionFragment
         final PlotEditFunctionFragment fragment = new PlotEditFunctionFragment();
         if (pf != null && pf.function instanceof ExpressionFunction) {
             final Bundle args = new Bundle();
-            final String name =
-                pf.function.hasName() ? Strings.nullToEmpty(pf.function.getName()) : "";
-            final List<String> parameters = new ArrayList<>();
             final ExpressionFunction ef = (ExpressionFunction) pf.function;
-            if (ef.xVariable != null) {
-                parameters.add(ef.xVariable.getName());
-            }
-            if (ef.yVariable != null) {
-                parameters.add(ef.yVariable.getName());
-            }
+            final List<String> parameters = new ArrayList<>(((CustomFunction) ef.function).getParameterNames());
             args.putParcelable(ARG_FUNCTION, CppFunction
-                .builder(name,
-                    ((CustomFunction) ef.function).getContent())
-                .withParameters(parameters)
-                .withId(pf.function.getId())
-                .build());
+                    .builder(ef.function.getName(),
+                            ((CustomFunction) ef.function).getContent())
+                    .withParameters(parameters)
+                    .withId(pf.function.getId())
+                    .build());
             fragment.setArguments(args);
         }
         return fragment;
@@ -168,7 +158,7 @@ public class PlotEditFunctionFragment extends BaseFunctionFragment
             final Constant x = parameters.size() > 0 ? new Constant(parameters.get(0)) : null;
             final Constant y = parameters.size() > 1 ? new Constant(parameters.get(1)) : null;
             final ExpressionFunction expressionFunction =
-                new ExpressionFunction(function.toJsclBuilder().create(), x, y, false);
+                new ExpressionFunction(function.toJsclBuilder().create(), false);
             final PlotFunction plotFunction = PlotFunction.create(expressionFunction,
                 applyMeshSpec());
             final int id = function.getId();
diff --git a/jscl/src/main/java/jscl/math/NumericWrapper.java b/jscl/src/main/java/jscl/math/NumericWrapper.java
index f0be0556..09ed7ab4 100644
--- a/jscl/src/main/java/jscl/math/NumericWrapper.java
+++ b/jscl/src/main/java/jscl/math/NumericWrapper.java
@@ -1,5 +1,11 @@
 package jscl.math;
 
+import java.math.BigInteger;
+import java.util.Collections;
+import java.util.Set;
+
+import javax.annotation.Nonnull;
+
 import jscl.JsclMathEngine;
 import jscl.math.function.Constant;
 import jscl.math.function.Constants;
@@ -11,12 +17,6 @@ import jscl.math.numeric.Real;
 import jscl.math.numeric.Vector;
 import jscl.mathml.MathML;
 
-import java.math.BigInteger;
-import java.util.Collections;
-import java.util.Set;
-
-import javax.annotation.Nonnull;
-
 public final class NumericWrapper extends Generic implements INumeric<NumericWrapper> {
 
     @Nonnull
@@ -185,7 +185,7 @@ public final class NumericWrapper extends Generic implements INumeric<NumericWra
     }
 
     public Generic substitute(@Nonnull Variable variable, Generic generic) {
-        return null;
+        return this;
     }
 
     public Generic expand() {