diff --git a/calculatorpp-core/src/main/java/org/solovyev/android/calculator/CalculatorEventType.java b/calculatorpp-core/src/main/java/org/solovyev/android/calculator/CalculatorEventType.java
index 34a71f50..24c7a9d3 100644
--- a/calculatorpp-core/src/main/java/org/solovyev/android/calculator/CalculatorEventType.java
+++ b/calculatorpp-core/src/main/java/org/solovyev/android/calculator/CalculatorEventType.java
@@ -115,6 +115,16 @@ public enum CalculatorEventType {
     // @NotNull IConstant
     constant_removed,
 
+
+	// @NotNull Function
+	function_removed,
+
+	// @NotNull Function
+	function_added,
+
+	// @NotNull Change<Function>
+	function_changed,
+
     /*
     **********************************************************************
     *
diff --git a/calculatorpp-core/src/main/java/org/solovyev/android/calculator/CalculatorFunctionsMathRegistry.java b/calculatorpp-core/src/main/java/org/solovyev/android/calculator/CalculatorFunctionsMathRegistry.java
index 20757ae1..9c57ac93 100644
--- a/calculatorpp-core/src/main/java/org/solovyev/android/calculator/CalculatorFunctionsMathRegistry.java
+++ b/calculatorpp-core/src/main/java/org/solovyev/android/calculator/CalculatorFunctionsMathRegistry.java
@@ -9,11 +9,14 @@ package org.solovyev.android.calculator;
 import jscl.math.function.CustomFunction;
 import jscl.math.function.Function;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 import org.solovyev.android.calculator.model.AFunction;
 import org.solovyev.android.calculator.model.Functions;
+import org.solovyev.android.calculator.model.MathEntityBuilder;
 import org.solovyev.common.JBuilder;
 import org.solovyev.common.math.MathRegistry;
 
+import java.util.Arrays;
 import java.util.HashMap;
 import java.util.Map;
 
@@ -42,7 +45,24 @@ public class CalculatorFunctionsMathRegistry extends AbstractCalculatorMathRegis
 	public void load() {
 		super.load();
 
-		add(new CustomFunction.Builder(true, "log", new String[]{"base", "x"}, "ln(x)/ln(base)"));
+		add(new CustomFunction.Builder(true, "log", Arrays.asList("base", "x"), "ln(x)/ln(base)"));
+	}
+
+	public static void saveFunction(@NotNull CalculatorMathRegistry<Function> registry,
+									@NotNull MathEntityBuilder<? extends Function> builder,
+									@Nullable Function editedInstance,
+									@NotNull Object source, boolean save) {
+		final Function addedFunction = registry.add(builder);
+
+		if (save) {
+			registry.save();
+		}
+
+		if (editedInstance == null) {
+			CalculatorLocatorImpl.getInstance().getCalculator().fireCalculatorEvent(CalculatorEventType.function_added, addedFunction, source);
+		} else {
+			CalculatorLocatorImpl.getInstance().getCalculator().fireCalculatorEvent(CalculatorEventType.function_changed, ChangeImpl.newInstance(editedInstance, addedFunction), source);
+		}
 	}
 
 	@NotNull
@@ -65,7 +85,9 @@ public class CalculatorFunctionsMathRegistry extends AbstractCalculatorMathRegis
 	@NotNull
 	@Override
 	protected JBuilder<? extends Function> createBuilder(@NotNull AFunction entity) {
-		return new CustomFunction.Builder(entity.getName(), entity.getParameterNamesAsArray(), entity.getContent());
+		CustomFunction.Builder builder = new CustomFunction.Builder(entity.getName(), entity.getParameterNames(), entity.getContent());
+		builder.setDescription(entity.getDescription());
+		return builder;
 	}
 
     @Override
diff --git a/calculatorpp-core/src/main/java/org/solovyev/android/calculator/model/AFunction.java b/calculatorpp-core/src/main/java/org/solovyev/android/calculator/model/AFunction.java
index 24df6db6..9b2e68a8 100644
--- a/calculatorpp-core/src/main/java/org/solovyev/android/calculator/model/AFunction.java
+++ b/calculatorpp-core/src/main/java/org/solovyev/android/calculator/model/AFunction.java
@@ -6,15 +6,17 @@
 
 package org.solovyev.android.calculator.model;
 
+import jscl.math.function.IConstant;
+import jscl.math.function.IFunction;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.simpleframework.xml.Element;
 import org.simpleframework.xml.Root;
+import org.simpleframework.xml.Transient;
 import org.solovyev.android.calculator.MathPersistenceEntity;
-import org.solovyev.common.collections.CollectionsUtils;
-import org.solovyev.common.text.CollectionTransformations;
-import org.solovyev.common.text.StringMapper;
+import org.solovyev.common.math.MathEntity;
 
+import java.util.Collections;
 import java.util.List;
 
 /**
@@ -24,7 +26,17 @@ import java.util.List;
  */
 
 @Root
-public class AFunction implements MathPersistenceEntity {
+public class AFunction implements IFunction, MathPersistenceEntity {
+
+	/*
+	**********************************************************************
+	*
+	*                           FIELDS
+	*
+	**********************************************************************
+	*/
+	@Transient
+	private Integer id;
 
 	@Element
 	@NotNull
@@ -34,17 +46,95 @@ public class AFunction implements MathPersistenceEntity {
 	@NotNull
 	private String content;
 
+	@Element(required = false)
+	@NotNull
+	private List<String> parameterNames = Collections.emptyList();
+
+	@Element
+	private boolean system;
 
 	@Element(required = false)
 	@Nullable
-	private String parameterNames;
+	private String description;
 
+	/*
+	**********************************************************************
+	*
+	*                           CONSTRUCTORS
+	*
+	**********************************************************************
+	*/
+
+	public AFunction() {
+	}
+
+	public AFunction(Integer id) {
+		this.id = id;
+	}
+
+	/*
+	**********************************************************************
+	*
+	*                           METHODS
+	*
+	**********************************************************************
+	*/
+
+	@Override
+	public void copy(@NotNull MathEntity mathEntity) {
+		if (mathEntity instanceof IFunction) {
+			final IFunction that = ((IFunction) mathEntity);
+			this.name = that.getName();
+			this.content = that.getContent();
+			this.description = this.getContent();
+			this.system = that.isSystem();
+			if (that.isIdDefined()) {
+				this.id = that.getId();
+			}
+		} else {
+			throw new IllegalArgumentException("Trying to make a copy of unsupported type: " + mathEntity.getClass());
+		}
+	}
+
+	@Override
+	public String toJava() {
+		return String.valueOf(this.content);
+	}
+
+	/*
+	**********************************************************************
+	*
+	*                           GETTERS/SEETTERS
+	*
+	**********************************************************************
+	*/
 
 	@NotNull
 	public String getName() {
 		return name;
 	}
 
+	@Override
+	public boolean isSystem() {
+		return system;
+	}
+
+	@NotNull
+	@Override
+	public Integer getId() {
+		return this.id;
+	}
+
+	@Override
+	public boolean isIdDefined() {
+		return this.id != null;
+	}
+
+	@Override
+	public void setId(@NotNull Integer id) {
+		this.id = id;
+	}
+
 	public void setName(@NotNull String name) {
 		this.name = name;
 	}
@@ -54,26 +144,128 @@ public class AFunction implements MathPersistenceEntity {
 		return content;
 	}
 
+	@Nullable
+	@Override
+	public String getDescription() {
+		return this.description;
+	}
+
 	public void setContent(@NotNull String content) {
 		this.content = content;
 	}
 
-	@Nullable
-	public String getParameterNames() {
+	@NotNull
+	public List<String> getParameterNames() {
 		return parameterNames;
 	}
 
-	public void setParameterNames(@Nullable String[] parameterNames) {
-		this.parameterNames = CollectionTransformations.formatValue(CollectionsUtils.asList(parameterNames), ";", new StringMapper());
-	}
-
-	public void setParameterNames(@Nullable String parameterNames) {
+	public void setParameterNames(@NotNull List<String> parameterNames) {
 		this.parameterNames = parameterNames;
 	}
 
-	@NotNull
-	public String[] getParameterNamesAsArray() {
-		final List<String> parameterNamesAsList = CollectionTransformations.split(parameterNames, ";");
-		return parameterNamesAsList.toArray(new String[parameterNamesAsList.size()]);
+	/*
+	**********************************************************************
+	*
+	*                           STATIC
+	*
+	**********************************************************************
+	*/
+
+	public static class Builder implements MathEntityBuilder<AFunction> {
+
+		@NotNull
+		private String name;
+
+		@Nullable
+		private String value;
+
+		private boolean system = false;
+
+		@Nullable
+		private String description;
+
+		@Nullable
+		private Integer id;
+
+		@NotNull
+		private List<String> parameterNames = Collections.emptyList();
+
+		public Builder() {
+		}
+
+		public Builder(@NotNull IFunction function) {
+			this.name = function.getName();
+			this.value = function.getContent();
+			this.system = function.isSystem();
+			this.description = function.getDescription();
+			this.id = function.getId();
+		}
+
+		public Builder(@NotNull IConstant function) {
+			this.name = function.getName();
+
+			this.value = function.getValue();
+
+			this.system = function.isSystem();
+			this.description = function.getDescription();
+			if (function.isIdDefined()) {
+				this.id = function.getId();
+			}
+		}
+
+		public Builder(@NotNull String name, @NotNull Double value) {
+			this(name, String.valueOf(value));
+		}
+
+		public Builder(@NotNull String name, @Nullable String value) {
+			this.name = name;
+			this.value = value;
+		}
+
+
+		@NotNull
+		public Builder setName(@NotNull String name) {
+			this.name = name;
+			return this;
+		}
+
+		@NotNull
+		public Builder setValue(@Nullable String value) {
+			this.value = value;
+			return this;
+		}
+
+		protected Builder setSystem(boolean system) {
+			this.system = system;
+			return this;
+		}
+
+		public void setParameterNames(@NotNull List<String> parameterNames) {
+			this.parameterNames = parameterNames;
+		}
+
+		@NotNull
+		public Builder setDescription(@Nullable String description) {
+			this.description = description;
+			return this;
+		}
+
+		@NotNull
+		public AFunction create() {
+			final AFunction result;
+			if (id != null) {
+				result = new AFunction(id);
+			} else {
+				result = new AFunction();
+			}
+
+			result.name = name;
+			result.content = value;
+			result.system = system;
+			result.description = description;
+			result.parameterNames = parameterNames;
+
+			return result;
+		}
 	}
 }
diff --git a/calculatorpp-core/src/main/java/org/solovyev/android/calculator/model/Functions.java b/calculatorpp-core/src/main/java/org/solovyev/android/calculator/model/Functions.java
index fd674f98..59d6a951 100644
--- a/calculatorpp-core/src/main/java/org/solovyev/android/calculator/model/Functions.java
+++ b/calculatorpp-core/src/main/java/org/solovyev/android/calculator/model/Functions.java
@@ -1,6 +1,5 @@
 package org.solovyev.android.calculator.model;
 
-import jscl.math.function.CustomFunction;
 import org.simpleframework.xml.ElementList;
 import org.simpleframework.xml.Root;
 import org.solovyev.android.calculator.MathEntityPersistenceContainer;
@@ -16,7 +15,7 @@ import java.util.List;
 @Root
 public class Functions implements MathEntityPersistenceContainer<AFunction> {
 
-	@ElementList(type = CustomFunction.class)
+	@ElementList(type = AFunction.class)
 	private List<AFunction> functions = new ArrayList<AFunction>();
 
 	public Functions() {
diff --git a/calculatorpp/res/layout/function_add_param.xml b/calculatorpp/res/layout/function_add_param.xml
new file mode 100644
index 00000000..9846a28e
--- /dev/null
+++ b/calculatorpp/res/layout/function_add_param.xml
@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="utf-8"?>
+
+<LinearLayout xmlns:a="http://schemas.android.com/apk/res/android"
+    a:layout_height="wrap_content"
+    a:layout_width="match_parent"
+    a:orientation="horizontal">
+
+    <Button
+        a:id="@+id/function_add_param_button"
+        a:layout_height="wrap_content"
+        a:layout_width="wrap_content"
+        a:text="+" />
+
+</LinearLayout>
diff --git a/calculatorpp/res/layout/function_edit.xml b/calculatorpp/res/layout/function_edit.xml
index 72cf9a1f..7cd4d2a3 100644
--- a/calculatorpp/res/layout/function_edit.xml
+++ b/calculatorpp/res/layout/function_edit.xml
@@ -33,15 +33,10 @@
             style="@style/default_text_size"
             a:text="@string/c_function_parameters"/>
 
-        <LinearLayout
-            a:id="@+id/function_params_layout"
+        <org.solovyev.android.calculator.function.FunctionParamsView
+			a:id="@+id/function_params_layout"
             a:layout_height="wrap_content"
-            a:layout_width="match_parent"
-            a:orientation="vertical">
-
-            <include layout="@layout/function_edit_param" />
-
-        </LinearLayout>
+            a:layout_width="match_parent"/>
 
         <TextView a:layout_height="wrap_content"
             a:layout_width="match_parent"
diff --git a/calculatorpp/res/layout/function_edit_param.xml b/calculatorpp/res/layout/function_edit_param.xml
index 61b0fdbe..d1469510 100644
--- a/calculatorpp/res/layout/function_edit_param.xml
+++ b/calculatorpp/res/layout/function_edit_param.xml
@@ -5,21 +5,27 @@
     a:layout_width="match_parent"
     a:orientation="horizontal">
 
-    <Button
-        a:id="@+id/function_add_param_button"
-        a:layout_height="wrap_content"
-        a:layout_width="wrap_content"
-        a:text="+" />
-
     <Button
         a:id="@+id/function_remove_param_button"
         a:layout_height="wrap_content"
         a:layout_width="wrap_content"
-        a:visibility="gone"
         a:text="-" />
 
+	<Button
+			a:id="@+id/function_up_param_button"
+			a:layout_height="wrap_content"
+			a:layout_width="wrap_content"
+			a:text="^" />
+
+	<Button
+			a:id="@+id/function_down_param_button"
+			a:layout_height="wrap_content"
+			a:layout_width="wrap_content"
+			a:text="v" />
+
     <EditText
-        a:layout_height="wrap_content"
+		a:id="@+id/function_param_edit_text"
+		a:layout_height="wrap_content"
         a:layout_width="match_parent"
         style="@style/default_text_size"
         a:inputType="text" />
diff --git a/calculatorpp/res/values/text_strings.xml b/calculatorpp/res/values/text_strings.xml
index c4a387a7..3a28e6fa 100644
--- a/calculatorpp/res/values/text_strings.xml
+++ b/calculatorpp/res/values/text_strings.xml
@@ -239,4 +239,12 @@
     <string name="c_function_description">Description</string>
     <string name="c_function_parameters">Parameters</string>
 
+	<string name="function_create_function">Create function</string>
+	<string name="function_edit_function">Edit function</string>
+	<string name="function_name_is_not_valid">Name of function is not valid: name must start with letter, can contain letters, digits and underscore.</string>
+	<string name="function_already_exists">Function with same name already exists!</string>
+	<string name="function_name_clashes">Function name clashes with function name!</string>
+	<string name="function_is_empty">Function body could not be empty!</string>
+	<string name="function_param_not_empty">Function parameter should not be empty!</string>
+
 </resources>
\ No newline at end of file
diff --git a/calculatorpp/src/main/java/org/solovyev/android/calculator/function/FunctionEditDialogFragment.java b/calculatorpp/src/main/java/org/solovyev/android/calculator/function/FunctionEditDialogFragment.java
index 1af5af78..2d4f69b5 100644
--- a/calculatorpp/src/main/java/org/solovyev/android/calculator/function/FunctionEditDialogFragment.java
+++ b/calculatorpp/src/main/java/org/solovyev/android/calculator/function/FunctionEditDialogFragment.java
@@ -1,6 +1,5 @@
 package org.solovyev.android.calculator.function;
 
-import android.content.Context;
 import android.os.Bundle;
 import android.support.v4.app.DialogFragment;
 import android.support.v4.app.FragmentManager;
@@ -8,10 +7,18 @@ import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
 import jscl.math.function.CustomFunction;
+import jscl.math.function.Function;
+import jscl.math.function.IFunction;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.solovyev.android.AndroidUtils2;
-import org.solovyev.android.calculator.*;
+import org.solovyev.android.calculator.CalculatorEventData;
+import org.solovyev.android.calculator.CalculatorEventListener;
+import org.solovyev.android.calculator.CalculatorEventType;
+import org.solovyev.android.calculator.CalculatorLocatorImpl;
+import org.solovyev.android.calculator.R;
+import org.solovyev.android.calculator.math.edit.MathEntityRemover;
+import org.solovyev.android.calculator.model.AFunction;
 
 /**
  * User: serso
@@ -23,7 +30,10 @@ public class FunctionEditDialogFragment extends DialogFragment implements Calcul
     @NotNull
     private final Input input;
 
-    public FunctionEditDialogFragment() {
+	@NotNull
+	private FunctionParamsView paramsView;
+
+	public FunctionEditDialogFragment() {
         this(Input.newInstance());
     }
 
@@ -40,26 +50,40 @@ public class FunctionEditDialogFragment extends DialogFragment implements Calcul
     public void onViewCreated(@NotNull View root, Bundle savedInstanceState) {
         super.onViewCreated(root, savedInstanceState);
 
-        final View addParamButton = root.findViewById(R.id.function_add_param_button);
+		paramsView = (FunctionParamsView) root.findViewById(R.id.function_params_layout);
 
-        final ViewGroup functionParamsLayout = (ViewGroup) root.findViewById(R.id.function_params_layout);
-        addParamButton.setOnClickListener(new View.OnClickListener() {
-            @Override
-            public void onClick(View v) {
-                final LayoutInflater inflater = (LayoutInflater) getActivity().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
-                final View functionEditParamLayout = inflater.inflate(R.layout.function_edit_param, null);
+		final AFunction.Builder builder;
+		final IFunction function = input.getFunction();
+		if (function != null) {
+			builder = new AFunction.Builder(function);
+			paramsView.init(function.getParameterNames());
+		} else {
+			builder = new AFunction.Builder();
+			paramsView.init();
+		}
 
-                final View addParamButton = functionEditParamLayout.findViewById(R.id.function_add_param_button);
-                addParamButton.setVisibility(View.GONE);
+		root.findViewById(R.id.cancel_button).setOnClickListener(new View.OnClickListener() {
+			@Override
+			public void onClick(View v) {
+				dismiss();
+			}
+		});
 
-                final View removeParamButton = functionEditParamLayout.findViewById(R.id.function_remove_param_button);
-                removeParamButton.setVisibility(View.VISIBLE);
+		root.findViewById(R.id.save_button).setOnClickListener(new FunctionEditorSaver(builder, function, root, CalculatorLocatorImpl.getInstance().getEngine().getFunctionsRegistry(), this));
 
-                functionParamsLayout.addView(functionEditParamLayout, new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT));
-            }
-        });
+		if ( function == null ) {
+			// CREATE MODE
+			getDialog().setTitle(R.string.function_create_function);
 
-    }
+			root.findViewById(R.id.remove_button).setVisibility(View.GONE);
+		} else {
+			// EDIT MODE
+			getDialog().setTitle(R.string.function_edit_function);
+
+			Function customFunction = new CustomFunction.Builder(function).create();
+			root.findViewById(R.id.remove_button).setOnClickListener(new MathEntityRemover<Function>(customFunction, null, CalculatorLocatorImpl.getInstance().getEngine().getFunctionsRegistry(), getActivity(), this));
+		}
+	}
 
     @Override
     public void onResume() {
@@ -77,6 +101,16 @@ public class FunctionEditDialogFragment extends DialogFragment implements Calcul
 
     @Override
     public void onCalculatorEvent(@NotNull CalculatorEventData calculatorEventData, @NotNull CalculatorEventType calculatorEventType, @Nullable Object data) {
+		switch (calculatorEventType) {
+			case function_removed:
+			case function_added:
+			case function_changed:
+				if ( calculatorEventData.getSource() == this ) {
+					dismiss();
+				}
+				break;
+
+		}
     }
 
         /*
@@ -94,7 +128,7 @@ public class FunctionEditDialogFragment extends DialogFragment implements Calcul
     public static class Input {
 
         @Nullable
-        private CustomFunction function;
+        private IFunction function;
 
         @Nullable
         private String name;
@@ -114,7 +148,7 @@ public class FunctionEditDialogFragment extends DialogFragment implements Calcul
         }
 
         @NotNull
-        public static Input newFromFunction(@NotNull CustomFunction function) {
+        public static Input newFromFunction(@NotNull IFunction function) {
             final Input result = new Input();
             result.function = function;
             return result;
@@ -128,7 +162,7 @@ public class FunctionEditDialogFragment extends DialogFragment implements Calcul
         }
 
         @NotNull
-        public static Input newInstance(@Nullable CustomFunction function, @Nullable String name, @Nullable String value, @Nullable String description) {
+        public static Input newInstance(@Nullable IFunction function, @Nullable String name, @Nullable String value, @Nullable String description) {
             final Input result = new Input();
             result.function = function;
             result.name = name;
@@ -138,7 +172,7 @@ public class FunctionEditDialogFragment extends DialogFragment implements Calcul
         }
 
         @Nullable
-        public CustomFunction getFunction() {
+        public IFunction getFunction() {
             return function;
         }
 
diff --git a/calculatorpp/src/main/java/org/solovyev/android/calculator/function/FunctionEditorSaver.java b/calculatorpp/src/main/java/org/solovyev/android/calculator/function/FunctionEditorSaver.java
new file mode 100644
index 00000000..3fc5d6c8
--- /dev/null
+++ b/calculatorpp/src/main/java/org/solovyev/android/calculator/function/FunctionEditorSaver.java
@@ -0,0 +1,167 @@
+package org.solovyev.android.calculator.function;
+
+import android.view.View;
+import android.widget.EditText;
+import jscl.math.function.CustomFunction;
+import jscl.math.function.Function;
+import jscl.math.function.IFunction;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+import org.solovyev.android.calculator.CalculatorFunctionsMathRegistry;
+import org.solovyev.android.calculator.CalculatorLocatorImpl;
+import org.solovyev.android.calculator.CalculatorMathRegistry;
+import org.solovyev.android.calculator.R;
+import org.solovyev.android.calculator.math.MathType;
+import org.solovyev.android.calculator.math.edit.VarEditorSaver;
+import org.solovyev.android.calculator.model.AFunction;
+import org.solovyev.android.calculator.model.MathEntityBuilder;
+import org.solovyev.common.msg.MessageType;
+import org.solovyev.common.text.StringUtils;
+
+import java.util.List;
+
+public class FunctionEditorSaver implements View.OnClickListener {
+
+	@NotNull
+	private final Object source;
+
+	@NotNull
+	private final AFunction.Builder builder;
+
+	@Nullable
+	private final Function editedInstance;
+
+	@NotNull
+	private final View view;
+
+	@NotNull
+	private final CalculatorMathRegistry<Function> mathRegistry;
+
+
+	public FunctionEditorSaver(@NotNull AFunction.Builder builder,
+							   @Nullable IFunction editedInstance,
+							   @NotNull View view,
+							   @NotNull CalculatorMathRegistry<Function> registry,
+							   @NotNull Object source) {
+
+		this.builder = builder;
+		if (editedInstance instanceof Function || editedInstance == null) {
+			this.editedInstance = (Function)editedInstance;
+		} else {
+			throw new IllegalArgumentException();
+		}
+		this.view = view;
+		this.mathRegistry = registry;
+		this.source = source;
+	}
+
+	@Override
+	public void onClick(View v) {
+		final Integer error;
+
+		final EditText editName = (EditText) view.findViewById(R.id.function_edit_name);
+		String name = editName.getText().toString();
+
+		final EditText editValue = (EditText) view.findViewById(R.id.function_edit_value);
+		String content = editValue.getText().toString();
+
+		final EditText editDescription = (EditText) view.findViewById(R.id.function_edit_description);
+		String description = editDescription.getText().toString();
+
+		final FunctionParamsView editParams = (FunctionParamsView) view.findViewById(R.id.function_params_layout);
+		List<String> parameterNames = editParams.getParameterNames();
+
+		if (VarEditorSaver.isValidName(name)) {
+
+			boolean canBeSaved = false;
+
+			final Function entityFromRegistry = mathRegistry.get(name);
+			if (entityFromRegistry == null) {
+				canBeSaved = true;
+			} else if (editedInstance != null && entityFromRegistry.getId().equals(editedInstance.getId())) {
+				canBeSaved = true;
+			}
+
+			if (canBeSaved) {
+				if (validateParameters(parameterNames)) {
+					final MathType.Result mathType = MathType.getType(name, 0, false);
+
+					if (mathType.getMathType() == MathType.text || mathType.getMathType() == MathType.function ) {
+
+						if (!StringUtils.isEmpty(content)) {
+							builder.setParameterNames(parameterNames);
+							builder.setName(name);
+							builder.setDescription(description);
+							builder.setValue(content);
+							error = null;
+						} else {
+							error = R.string.function_is_empty;
+						}
+					} else {
+						error = R.string.function_name_clashes;
+					}
+				} else {
+					error = R.string.function_param_not_empty;
+				}
+			} else {
+				error = R.string.function_already_exists;
+			}
+		} else {
+			error = R.string.function_name_is_not_valid;
+		}
+
+		if (error != null) {
+			CalculatorLocatorImpl.getInstance().getNotifier().showMessage(error, MessageType.error);
+		} else {
+			CalculatorFunctionsMathRegistry.saveFunction(mathRegistry, new BuilderAdapter(builder), editedInstance, source, true);
+		}
+	}
+
+	private boolean validateParameters(@NotNull List<String> parameterNames) {
+		for (String parameterName : parameterNames) {
+			if ( !VarEditorSaver.isValidName(parameterName) ) {
+				return false;
+			}
+		}
+
+		return true;
+	}
+
+	private static final class BuilderAdapter implements MathEntityBuilder<Function> {
+
+		@NotNull
+		private final AFunction.Builder nestedBuilder;
+
+		public BuilderAdapter(@NotNull AFunction.Builder nestedBuilder) {
+			this.nestedBuilder = nestedBuilder;
+		}
+
+		@NotNull
+		@Override
+		public MathEntityBuilder<Function> setName(@NotNull String name) {
+			nestedBuilder.setName(name);
+			return this;
+		}
+
+		@NotNull
+		@Override
+		public MathEntityBuilder<Function> setDescription(@Nullable String description) {
+			nestedBuilder.setDescription(description);
+			return this;
+		}
+
+		@NotNull
+		@Override
+		public MathEntityBuilder<Function> setValue(@Nullable String value) {
+			nestedBuilder.setValue(value);
+			return this;
+		}
+
+		@NotNull
+		@Override
+		public Function create() {
+			final AFunction function = nestedBuilder.create();
+			return new CustomFunction.Builder(function).create();
+		}
+	}
+}
diff --git a/calculatorpp/src/main/java/org/solovyev/android/calculator/function/FunctionParamsView.java b/calculatorpp/src/main/java/org/solovyev/android/calculator/function/FunctionParamsView.java
new file mode 100644
index 00000000..e65f5fd7
--- /dev/null
+++ b/calculatorpp/src/main/java/org/solovyev/android/calculator/function/FunctionParamsView.java
@@ -0,0 +1,186 @@
+package org.solovyev.android.calculator.function;
+
+import android.content.Context;
+import android.util.AttributeSet;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.EditText;
+import android.widget.LinearLayout;
+import android.widget.TextView;
+import jscl.text.MutableInt;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+import org.solovyev.android.calculator.R;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+public class FunctionParamsView extends LinearLayout {
+
+	@NotNull
+	private final MutableInt paramsCount = new MutableInt(0);
+
+	@NotNull
+	private final List<Integer> paramIds = new ArrayList<Integer>(10);
+
+	private static final String PARAM_TAG_PREFIX = "function_param_";
+
+	public FunctionParamsView(Context context) {
+		super(context);
+	}
+
+	public FunctionParamsView(Context context, AttributeSet attrs) {
+		super(context, attrs);
+	}
+
+	public FunctionParamsView(Context context, AttributeSet attrs, int defStyle) {
+		super(context, attrs, defStyle);
+	}
+
+	public void init() {
+		init(Collections.<String>emptyList());
+	}
+
+	public void init(@NotNull List<String> parameters) {
+		this.setOrientation(VERTICAL);
+
+		final LayoutInflater inflater = (LayoutInflater) getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
+
+		final View addParamView = inflater.inflate(R.layout.function_add_param, null);
+
+		final View addParamButton = addParamView.findViewById(R.id.function_add_param_button);
+
+		addParamButton.setOnClickListener(new View.OnClickListener() {
+			@Override
+			public void onClick(View v) {
+				addParam(null);
+			}
+		});
+
+		this.addView(addParamView, new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT));
+
+		for (String parameter : parameters) {
+			addParam(parameter);
+		}
+	}
+
+	public void addParam(@Nullable String name) {
+		synchronized (paramsCount) {
+			final LayoutInflater inflater = (LayoutInflater) getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
+
+			final Integer id = paramsCount.intValue();
+
+			final View editParamView = inflater.inflate(R.layout.function_edit_param, null);
+
+			editParamView.setTag(getParamTag(id));
+
+			final View removeParamButton = editParamView.findViewById(R.id.function_remove_param_button);
+			removeParamButton.setOnClickListener(new OnClickListener() {
+				@Override
+				public void onClick(View v) {
+					removeParam(id);
+				}
+			});
+
+			final View upParamButton = editParamView.findViewById(R.id.function_up_param_button);
+			upParamButton.setOnClickListener(new OnClickListener() {
+				@Override
+				public void onClick(View v) {
+					upParam(id);
+				}
+			});
+
+			final View downParamButton = editParamView.findViewById(R.id.function_down_param_button);
+			downParamButton.setOnClickListener(new OnClickListener() {
+				@Override
+				public void onClick(View v) {
+					downParam(id);
+				}
+			});
+
+			this.addView(editParamView, new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT));
+
+			paramIds.add(id);
+			paramsCount.increment();
+		}
+	}
+
+	private void downParam(@NotNull Integer id) {
+		synchronized (paramsCount) {
+			int index = paramIds.indexOf(id);
+			if (index < paramIds.size() - 1) {
+				swap(index, index + 1);
+			}
+		}
+	}
+
+	private void upParam(@NotNull Integer id) {
+		synchronized (paramsCount) {
+			int index = paramIds.indexOf(id);
+			if (index > 0) {
+				swap(index, index - 1);
+			}
+		}
+	}
+
+	private void swap(int index1, int index2) {
+		final View editParamView1 = getParamView(paramIds.get(index1));
+		final View editParamView2 = getParamView(paramIds.get(index2));
+
+		if (editParamView1 != null && editParamView2 != null) {
+			final EditText paramNameEditText1 = (EditText) editParamView1.findViewById(R.id.function_param_edit_text);
+			final EditText paramNameEditText2 = (EditText) editParamView2.findViewById(R.id.function_param_edit_text);
+			swap(paramNameEditText1, paramNameEditText2);
+		}
+	}
+
+	private void swap(@NotNull TextView first,
+					  @NotNull TextView second) {
+		final CharSequence tmp = first.getText();
+		first.setText(second.getText());
+		second.setText(tmp);
+	}
+
+	@Nullable
+	private View getParamView(@NotNull Integer id) {
+		final String tag = getParamTag(id);
+		return this.findViewWithTag(tag);
+	}
+
+	@NotNull
+	 private String getParamTag(@NotNull Integer index) {
+		return PARAM_TAG_PREFIX + index;
+	}
+
+	public void removeParam(@NotNull Integer id) {
+		synchronized (paramsCount) {
+			if (paramIds.contains(id)) {
+				final View editParamView = getParamView(id);
+				if (editParamView != null) {
+					this.removeView(editParamView);
+					paramIds.remove(id);
+				}
+			}
+		}
+	}
+
+	@NotNull
+	public List<String> getParameterNames() {
+		synchronized (paramsCount) {
+			final List<String> result = new ArrayList<String>(paramsCount.intValue());
+
+			for (Integer id : paramIds) {
+				final View paramView = getParamView(id);
+				if ( paramView != null ) {
+					final EditText paramNameEditText = (EditText) paramView.findViewById(R.id.function_param_edit_text);
+					result.add(paramNameEditText.getText().toString());
+				}
+			}
+
+			return result;
+		}
+	}
+
+}
diff --git a/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/CalculatorFunctionsFragment.java b/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/CalculatorFunctionsFragment.java
index 5b578967..b594c2e0 100644
--- a/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/CalculatorFunctionsFragment.java
+++ b/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/CalculatorFunctionsFragment.java
@@ -16,6 +16,7 @@ import com.actionbarsherlock.view.MenuInflater;
 import com.actionbarsherlock.view.MenuItem;
 import jscl.math.function.CustomFunction;
 import jscl.math.function.Function;
+import jscl.math.function.IFunction;
 import org.jetbrains.annotations.NotNull;
 import org.solovyev.android.calculator.CalculatorEventType;
 import org.solovyev.android.calculator.CalculatorLocatorImpl;
@@ -244,24 +245,24 @@ public class CalculatorFunctionsFragment extends AbstractMathEntityListFragment<
     private static enum LongClickMenuItem implements LabeledMenuItem<Function> {
         use(R.string.c_use) {
             @Override
-            public void onClick(@NotNull Function data, @NotNull Context context) {
-                CalculatorLocatorImpl.getInstance().getCalculator().fireCalculatorEvent(CalculatorEventType.use_function, data);
+            public void onClick(@NotNull Function function, @NotNull Context context) {
+                CalculatorLocatorImpl.getInstance().getCalculator().fireCalculatorEvent(CalculatorEventType.use_function, function);
             }
         },
 
         edit(R.string.c_edit) {
             @Override
             public void onClick(@NotNull Function function, @NotNull Context context) {
-                if (function instanceof CustomFunction) {
-                    FunctionEditDialogFragment.showDialog(FunctionEditDialogFragment.Input.newFromFunction((CustomFunction) function), ((SherlockFragmentActivity) context).getSupportFragmentManager());
-                }
-            }
+				if (function instanceof IFunction) {
+					FunctionEditDialogFragment.showDialog(FunctionEditDialogFragment.Input.newFromFunction((IFunction) function), ((SherlockFragmentActivity) context).getSupportFragmentManager());
+				}
+			}
         },
 
         copy_description(R.string.c_copy_description) {
             @Override
-            public void onClick(@NotNull Function data, @NotNull Context context) {
-                final String text = CalculatorLocatorImpl.getInstance().getEngine().getFunctionsRegistry().getDescription(data.getName());
+            public void onClick(@NotNull Function function, @NotNull Context context) {
+                final String text = CalculatorLocatorImpl.getInstance().getEngine().getFunctionsRegistry().getDescription(function.getName());
                 if (!StringUtils.isEmpty(text)) {
                     final ClipboardManager clipboard = (ClipboardManager) context.getSystemService(Activity.CLIPBOARD_SERVICE);
                     clipboard.setText(text);
diff --git a/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/MathEntityRemover.java b/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/MathEntityRemover.java
index dc2db31d..7a9d20fe 100644
--- a/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/MathEntityRemover.java
+++ b/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/MathEntityRemover.java
@@ -24,7 +24,7 @@ import org.solovyev.common.math.MathEntity;
  * Date: 12/22/11
  * Time: 9:36 PM
  */
-class MathEntityRemover<T extends MathEntity> implements View.OnClickListener, DialogInterface.OnClickListener {
+public class MathEntityRemover<T extends MathEntity> implements View.OnClickListener, DialogInterface.OnClickListener {
 
 	@NotNull
 	private final T mathEntity;
diff --git a/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/VarEditorSaver.java b/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/VarEditorSaver.java
index 64e29d75..7bbf1828 100644
--- a/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/VarEditorSaver.java
+++ b/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/VarEditorSaver.java
@@ -29,7 +29,7 @@ import org.solovyev.common.text.StringUtils;
  * Date: 12/22/11
  * Time: 9:52 PM
  */
-class VarEditorSaver<T extends MathEntity> implements View.OnClickListener {
+public class VarEditorSaver<T extends MathEntity> implements View.OnClickListener {
 
 	@NotNull
 	private final MathEntityBuilder<? extends T> varBuilder;
@@ -123,7 +123,7 @@ class VarEditorSaver<T extends MathEntity> implements View.OnClickListener {
         }
     }
 
-    boolean isValidName(@Nullable String name) {
+    public static boolean isValidName(@Nullable String name) {
 		boolean result = false;
 
 		if (!StringUtils.isEmpty(name)) {
diff --git a/calculatorpp/src/main/java/org/solovyev/android/calculator/model/AndroidCalculatorEngine.java b/calculatorpp/src/main/java/org/solovyev/android/calculator/model/AndroidCalculatorEngine.java
index 0cd96f89..2f0507c0 100644
--- a/calculatorpp/src/main/java/org/solovyev/android/calculator/model/AndroidCalculatorEngine.java
+++ b/calculatorpp/src/main/java/org/solovyev/android/calculator/model/AndroidCalculatorEngine.java
@@ -17,7 +17,16 @@ import jscl.math.function.Function;
 import jscl.math.function.IConstant;
 import jscl.math.operator.Operator;
 import org.jetbrains.annotations.NotNull;
-import org.solovyev.android.calculator.*;
+import org.solovyev.android.calculator.CalculatorEngine;
+import org.solovyev.android.calculator.CalculatorEngineImpl;
+import org.solovyev.android.calculator.CalculatorFunctionsMathRegistry;
+import org.solovyev.android.calculator.CalculatorMathEngine;
+import org.solovyev.android.calculator.CalculatorMathRegistry;
+import org.solovyev.android.calculator.CalculatorOperatorsMathRegistry;
+import org.solovyev.android.calculator.CalculatorPostfixFunctionsRegistry;
+import org.solovyev.android.calculator.CalculatorVarsRegistry;
+import org.solovyev.android.calculator.MathPersistenceEntity;
+import org.solovyev.android.calculator.R;
 import org.solovyev.android.prefs.BooleanPreference;
 import org.solovyev.android.prefs.Preference;
 import org.solovyev.android.prefs.StringPreference;