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 377560ac..15b693e7 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
@@ -93,7 +93,7 @@ public class ExpressionFunction extends Function {
 
     public float unwrap(Numeric content) {
         if (content instanceof Real) {
-            return (float) ((Real) content).doubleValue();
+            return (float) content.doubleValue();
         }
         if (content instanceof Complex) {
             return (float) (imaginary ? ((Complex) content).imaginaryPart() : ((Complex) content).realPart());
diff --git a/jscl/src/main/java/jscl/math/Expression.java b/jscl/src/main/java/jscl/math/Expression.java
index 63d94eef..6a9759c5 100644
--- a/jscl/src/main/java/jscl/math/Expression.java
+++ b/jscl/src/main/java/jscl/math/Expression.java
@@ -512,7 +512,9 @@ public class Expression extends Generic {
             for (int j = 0; j < literal.size(); j++) {
                 final Variable variable = literal.getVariable(j);
 
-                Generic b = content.get(variable).pow(literal.getPower(j));
+                final int power = literal.getPower(j);
+                final Generic contentVariable = content.get(variable);
+                Generic b = pow(contentVariable, power);
 
                 if (Matrix.isMatrixProduct(sumElement, b)) {
                     throw new ArithmeticException("Should not be matrix!");
@@ -527,6 +529,18 @@ public class Expression extends Generic {
         return sum;
     }
 
+    @Nonnull
+    private Generic pow(@Nonnull Generic g, int power) {
+        switch (power) {
+            case 0:
+                return JsclInteger.valueOf(1);
+            case 1:
+                return g;
+            default:
+                return g.pow(power);
+        }
+    }
+
     public Generic expand() {
         return substitute(literalScm().content(EXPAND_CONVERTER));
     }
diff --git a/jscl/src/main/java/jscl/math/JsclInteger.java b/jscl/src/main/java/jscl/math/JsclInteger.java
index 5339e192..a8fc3efa 100644
--- a/jscl/src/main/java/jscl/math/JsclInteger.java
+++ b/jscl/src/main/java/jscl/math/JsclInteger.java
@@ -46,6 +46,9 @@ public final class JsclInteger extends Generic {
 
     @Nonnull
     public Generic add(@Nonnull Generic that) {
+        if (isZero()) {
+            return that;
+        }
         if (that instanceof JsclInteger) {
             return add((JsclInteger) that);
         } else {
@@ -53,8 +56,15 @@ public final class JsclInteger extends Generic {
         }
     }
 
-    public JsclInteger subtract(JsclInteger integer) {
-        return new JsclInteger(content.subtract(integer.content));
+    private boolean isZero() {
+        return content.equals(ZERO.content);
+    }
+
+    public JsclInteger subtract(JsclInteger that) {
+        if(isZero()) {
+            return that.negate();
+        }
+        return new JsclInteger(content.subtract(that.content));
     }
 
     @Nonnull
@@ -72,6 +82,9 @@ public final class JsclInteger extends Generic {
 
     @Nonnull
     public Generic multiply(@Nonnull Generic that) {
+        if (isOne()) {
+            return that;
+        }
         if (that instanceof JsclInteger) {
             return multiply((JsclInteger) that);
         } else {
@@ -79,7 +92,14 @@ public final class JsclInteger extends Generic {
         }
     }
 
+    private boolean isOne() {
+        return content.equals(ONE.content);
+    }
+
     public JsclInteger divide(@Nonnull JsclInteger that) {
+        if (isZero()) {
+            return ZERO;
+        }
         JsclInteger e[] = divideAndRemainder(that);
         if (e[1].signum() == 0) {
             return e[0];
@@ -149,7 +169,7 @@ public final class JsclInteger extends Generic {
         return new JsclInteger(content.pow(exponent));
     }
 
-    public Generic negate() {
+    public JsclInteger negate() {
         return new JsclInteger(content.negate());
     }
 
diff --git a/jscl/src/main/java/jscl/math/Literal.java b/jscl/src/main/java/jscl/math/Literal.java
index 0db4bcf6..66fa9f52 100644
--- a/jscl/src/main/java/jscl/math/Literal.java
+++ b/jscl/src/main/java/jscl/math/Literal.java
@@ -8,6 +8,7 @@ import jscl.mathml.MathML;
 
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
+import java.util.HashMap;
 import java.util.Iterator;
 import java.util.Map;
 import java.util.TreeMap;
@@ -382,7 +383,7 @@ public class Literal implements Comparable {
     }
 
     Map<Variable, Generic> content(@Nonnull Function<Variable, Generic> c) {
-        final Map<Variable, Generic> result = new TreeMap<Variable, Generic>();
+        final Map<Variable, Generic> result = new HashMap<>(size);
 
         for (int i = 0; i < size; i++) {
             result.put(variables[i], c.apply(variables[i]));
diff --git a/jscl/src/main/java/jscl/math/function/CustomFunction.java b/jscl/src/main/java/jscl/math/function/CustomFunction.java
index 45674cb3..cd4c2b6a 100644
--- a/jscl/src/main/java/jscl/math/function/CustomFunction.java
+++ b/jscl/src/main/java/jscl/math/function/CustomFunction.java
@@ -1,5 +1,6 @@
 package jscl.math.function;
 
+import com.google.common.collect.Lists;
 import jscl.CustomFunctionCalculationException;
 import jscl.JsclMathEngine;
 import jscl.math.*;
@@ -15,18 +16,17 @@ import java.util.concurrent.atomic.AtomicInteger;
 
 public class CustomFunction extends Function implements IFunction {
 
-    private static final String LOCAL_VAR_POSTFIX = "_lv_09_03_1988_";
-
     private final static AtomicInteger counter = new AtomicInteger(0);
 
-    @Nonnull
-    private final Integer localVarId;
+    private final int id;
     @Nonnull
     private Expression content;
     @Nullable
     private String description;
     @Nonnull
     private List<String> parameterNames = Collections.emptyList();
+    @Nullable
+    private List<ConstantData> parameterConstants;
 
     private CustomFunction(@Nonnull String name,
                            @Nonnull List<String> parameterNames,
@@ -36,7 +36,18 @@ public class CustomFunction extends Function implements IFunction {
         this.parameterNames = parameterNames;
         this.content = content;
         this.description = description;
-        this.localVarId = counter.incrementAndGet();
+        this.id = counter.incrementAndGet();
+    }
+
+    @Nonnull
+    private List<ConstantData> makeParameterConstants(@Nonnull List<String> names) {
+        return new ArrayList<>(Lists.transform(names, new com.google.common.base.Function<String, ConstantData>() {
+            @Nullable
+            @Override
+            public ConstantData apply(@Nullable String name) {
+                return new ConstantData(name);
+            }
+        }));
     }
 
     private CustomFunction(@Nonnull String name,
@@ -51,7 +62,7 @@ public class CustomFunction extends Function implements IFunction {
             throw new CustomFunctionCalculationException(this, e);
         }
         this.description = description;
-        this.localVarId = counter.incrementAndGet();
+        this.id = counter.incrementAndGet();
     }
 
     @Override
@@ -91,29 +102,27 @@ public class CustomFunction extends Function implements IFunction {
 
     @Override
     public Generic selfExpand() {
-        Generic localContent = content;
-
-        try {
-            for (String parameterName : parameterNames) {
-                localContent = localContent.substitute(new Constant(parameterName), Expression.valueOf(new Constant(getParameterNameForConstant(parameterName))));
-            }
-
-            for (int i = 0; i < parameterNames.size(); i++) {
-                localContent = localContent.substitute(new Constant(getParameterNameForConstant(parameterNames.get(i))), parameters[i]);
-            }
-
-        } finally {
-            for (String parameterName : parameterNames) {
-                localContent = localContent.substitute(new Constant(getParameterNameForConstant(parameterName)), Expression.valueOf(new Constant(parameterName)));
-            }
+        Generic content = this.content;
+        final List<ConstantData> parameterConstants = getParameterConstants();
+        for (ConstantData cd : parameterConstants) {
+            content = content.substitute(cd.local, cd.globalExpression);
         }
-
-        return localContent;
+        for (int i = 0; i < parameterConstants.size(); i++) {
+            final ConstantData cd = parameterConstants.get(i);
+            content = content.substitute(cd.global, parameters[i]);
+        }
+        for (ConstantData cd : parameterConstants) {
+            content = content.substitute(cd.global, cd.localExpression);
+        }
+        return content;
     }
 
     @Nonnull
-    private String getParameterNameForConstant(@Nonnull String parameterName) {
-        return parameterName + LOCAL_VAR_POSTFIX + "_" + this.localVarId;
+    private List<ConstantData> getParameterConstants() {
+        if(parameterConstants == null) {
+            parameterConstants = makeParameterConstants(parameterNames);
+        }
+        return parameterConstants;
     }
 
     @Override
@@ -328,4 +337,22 @@ public class CustomFunction extends Function implements IFunction {
             return customFunction;
         }
     }
+
+    private final class ConstantData {
+        @Nonnull
+        final Constant global;
+        @Nonnull
+        final Constant local;
+        @Nonnull
+        final Generic globalExpression;
+        @Nonnull
+        final Generic localExpression;
+
+        public ConstantData(@Nonnull String name) {
+            global = new Constant(name + "#" + id);
+            globalExpression = Expression.valueOf(global);
+            local = new Constant(name);
+            localExpression = Expression.valueOf(local);
+        }
+    }
 }