diff --git a/src/main/java/com/googlecode/aviator/AviatorEvaluator.java b/src/main/java/com/googlecode/aviator/AviatorEvaluator.java
index 8e516aa3..91b1cadf 100644
--- a/src/main/java/com/googlecode/aviator/AviatorEvaluator.java
+++ b/src/main/java/com/googlecode/aviator/AviatorEvaluator.java
@@ -430,7 +430,7 @@ public static AviatorFunction removeOpFunction(final OperatorType opType) {
 
 
   /**
-   * Check if the function is existed in aviator
+   * Check if the function exists in the global evaluator instance.
    *
    * @param name
    * @return
diff --git a/src/main/java/com/googlecode/aviator/AviatorEvaluatorInstance.java b/src/main/java/com/googlecode/aviator/AviatorEvaluatorInstance.java
index bb99aa04..8002bed7 100644
--- a/src/main/java/com/googlecode/aviator/AviatorEvaluatorInstance.java
+++ b/src/main/java/com/googlecode/aviator/AviatorEvaluatorInstance.java
@@ -1327,13 +1327,24 @@ public AviatorFunction removeOpFunction(final OperatorType opType) {
   }
 
   /**
-   * Check if the function is existed in aviator
+   * Check if the function exists in the evaluator. Note: it doesn't check the runtime defined
+   * functions.
    *
    * @param name
    * @return
    */
   public boolean containsFunction(final String name) {
-    return this.funcMap.containsKey(name);
+    boolean exists = this.funcMap.containsKey(name);
+    if (!exists && this.functionLoaders != null) {
+      for (FunctionLoader loader : this.functionLoaders) {
+        if (loader != null && loader.onFunctionNotFound(name) != null) {
+          exists = true;
+          break;
+        }
+      }
+    }
+
+    return exists;
   }
 
   /**
diff --git a/src/main/java/com/googlecode/aviator/BaseExpression.java b/src/main/java/com/googlecode/aviator/BaseExpression.java
index 6b2df0e4..835f2f85 100644
--- a/src/main/java/com/googlecode/aviator/BaseExpression.java
+++ b/src/main/java/com/googlecode/aviator/BaseExpression.java
@@ -42,8 +42,8 @@ public abstract class BaseExpression implements Expression {
   private static final long serialVersionUID = 2819544277750883372L;
 
   public static final String FUNC_PARAMS_VAR = "__funcs_args__";
-  protected List<String> varNames;
-  protected List<String> varFullNames;
+  protected transient List<String> varNames;
+  protected transient List<String> varFullNames;
   private List<VariableMeta> vars;
   private String expression;
   protected transient AviatorEvaluatorInstance instance;
@@ -53,6 +53,12 @@ public abstract class BaseExpression implements Expression {
   // cached compiled string segments for string interpolation.
   private transient ConcurrentHashMap<String, FutureTask<StringSegments>> stringSegs =
       new ConcurrentHashMap<String, FutureTask<StringSegments>>();
+  // The function name list in expression
+  private List<String> functionNames = Collections.emptyList();
+
+  // Already filtered function names, try to remove the runtime defined functions.
+  private transient List<String> filteredFunctionNames = null;
+
 
   protected String sourceFile;
   protected Map<String, LambdaFunctionBootstrap> lambdaBootstraps;
@@ -62,12 +68,12 @@ public String getSourceFile() {
     return this.sourceFile;
   }
 
-  public void setSourceFile(final String sourceFile) {
+  protected void setSourceFile(final String sourceFile) {
     this.sourceFile = sourceFile;
   }
 
 
-  public void setInstance(AviatorEvaluatorInstance instance) {
+  protected void setInstance(AviatorEvaluatorInstance instance) {
     this.instance = instance;
   }
 
@@ -264,7 +270,7 @@ protected Object execute(Map<String, Object> map, boolean checkExecutionTimeout)
     }
   }
 
-  public void setFuncsArgs(final Map<Integer, List<FunctionArgument>> funcsArgs) {
+  protected void setFuncsArgs(final Map<Integer, List<FunctionArgument>> funcsArgs) {
     if (funcsArgs != null) {
       this.funcsArgs = Collections.unmodifiableMap(funcsArgs);
     }
@@ -274,7 +280,7 @@ public Env getCompileEnv() {
     return this.compileEnv;
   }
 
-  public void setCompileEnv(final Env compileEnv) {
+  protected void setCompileEnv(final Env compileEnv) {
     this.compileEnv = compileEnv;
     this.compileEnv.setExpression(this);
   }
@@ -289,7 +295,7 @@ public String getExpression() {
     return this.expression;
   }
 
-  public void setExpression(final String expression) {
+  protected void setExpression(final String expression) {
     this.expression = expression;
   }
 
@@ -374,11 +380,57 @@ protected Env newEnv(final Map<String, Object> map) {
     return newEnv(map, false, true);
   }
 
+  public List<String> getFunctionNames() {
+    populateFilteredFuncNames();
+
+    return filteredFunctionNames;
+  }
+
+  private void populateFilteredFuncNames() {
+    if (this.filteredFunctionNames == null) {
+      Set<String> validNames = new HashSet<String>(this.functionNames.size());
+
+      for (String funcName : this.functionNames) {
+        // Remove internal functions
+        if (!funcName.startsWith("__") && !funcName.equals("with_meta")) {
+          validNames.add(funcName);
+        }
+      }
+
+      Set<String> definedFuncs = new HashSet<String>();
+      // Find all runtime defined functions
+      for (VariableMeta v : this.vars) {
+        // TODO: It's not precise, but could work
+        if (v.isInit()) {
+          definedFuncs.add(v.getName());
+        }
+      }
+
+      if (this.lambdaBootstraps != null) {
+        // Adds sub-expressions function names
+        for (LambdaFunctionBootstrap bootstrap : this.lambdaBootstraps.values()) {
+          validNames.addAll(bootstrap.getExpression().getFunctionNames());
+        }
+      }
+
+      // Remove runtime defined functions.
+      validNames.removeAll(definedFuncs);
+
+      this.filteredFunctionNames = new ArrayList<>(validNames);
+    }
+  }
+
+  protected void setFunctionNames(List<String> functionNames) {
+    if (functionNames != null) {
+      this.functionNames = functionNames;
+    }
+  }
+
   public Map<String, LambdaFunctionBootstrap> getLambdaBootstraps() {
     return this.lambdaBootstraps;
   }
 
-  public void setLambdaBootstraps(final Map<String, LambdaFunctionBootstrap> lambdaBootstraps) {
+  protected void setLambdaBootstraps(final Map<String, LambdaFunctionBootstrap> lambdaBootstraps) {
     this.lambdaBootstraps = lambdaBootstraps;
   }
 
@@ -400,6 +452,7 @@ public void customReadObject(ObjectInputStream input) throws ClassNotFoundExcept
     this.sourceFile = (String) input.readObject();
     this.lambdaBootstraps = (Map<String, LambdaFunctionBootstrap>) input.readObject();
     this.stringSegs = new ConcurrentHashMap<String, FutureTask<StringSegments>>();
+    this.functionNames = (List<String>) input.readObject();
   }
 
   public void customWriteObject(ObjectOutputStream output) throws IOException {
@@ -410,6 +463,7 @@ public void customWriteObject(ObjectOutputStream output) throws IOException {
     output.writeObject(this.symbolTable);
     output.writeObject(this.sourceFile);
     output.writeObject(this.lambdaBootstraps);
+    output.writeObject(this.functionNames);
   }
 
 }
diff --git a/src/main/java/com/googlecode/aviator/Expression.java b/src/main/java/com/googlecode/aviator/Expression.java
index b90bb69f..545632f3 100644
--- a/src/main/java/com/googlecode/aviator/Expression.java
+++ b/src/main/java/com/googlecode/aviator/Expression.java
@@ -29,18 +29,18 @@
 public interface Expression extends Serializable {
 
   /**
-   * Execute expression with environment
+   * Execute an expression with an environment, returns the result.
    *
    * @param env Binding variable environment
-   * @return
+   * @return the result of execution
    */
   Object execute(Map<String, Object> env);
 
 
   /**
-   * Execute expression with empty environment
+   * Execute an expression with an empty environment, returns the result.
    *
-   * @return
+   * @return the result of execution
    */
   Object execute();
 
@@ -55,7 +55,7 @@ public interface Expression extends Serializable {
 
   /**
    * Returns this expression's all uninitialized global variable names in order when using
-   * AviatorEvaluator.EVAL mode,else returns empty set
+   * AviatorEvaluator.EVAL mode, otherwise returns an empty list.
    *
    * @see com.googlecode.aviator.AviatorEvaluator#EVAL
    * @return
@@ -65,7 +65,7 @@ public interface Expression extends Serializable {
 
   /**
    * Returns this expression's all uninitialized global variable full names(contains dot) in order
-   * when using AviatorEvaluator.EVAL mode,else returns empty set
+   * when using AviatorEvaluator.EVAL mode, otherwise returns an empty list.
    *
    * @return
    */
@@ -89,4 +89,12 @@ public interface Expression extends Serializable {
    */
   String addSymbol(String name);
 
+  /**
+   * Returns the function names in the expression when using AviatorEvaluator.EVAL mode, otherwise
+   * returns an empty list.
+   * 
+   * @since 5.4.2
+   * @return the function name list
+   */
+  List<String> getFunctionNames();
 }
diff --git a/src/main/java/com/googlecode/aviator/ExpressionAccessor.java b/src/main/java/com/googlecode/aviator/ExpressionAccessor.java
new file mode 100644
index 00000000..5d0421ca
--- /dev/null
+++ b/src/main/java/com/googlecode/aviator/ExpressionAccessor.java
@@ -0,0 +1,61 @@
+/**
+ * Copyright (C) 2010 dennis zhuang (killme2008@gmail.com)
+ *
+ * This library is free software; you can redistribute it and/or modify it under the terms of the
+ * GNU Lesser General Public License as published by the Free Software Foundation; either version
+ * 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without
+ * even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License along with this program;
+ * if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ **/
+package com.googlecode.aviator;
+
+import java.util.List;
+import java.util.Map;
+import com.googlecode.aviator.runtime.FunctionArgument;
+import com.googlecode.aviator.runtime.LambdaFunctionBootstrap;
+import com.googlecode.aviator.utils.Env;
+
+/**
+ * Base expression default methods accessor
+ * 
+ * @author dennis
+ *
+ */
+public class ExpressionAccessor {
+
+  public static void setSourceFile(final BaseExpression exp, String sourceFile) {
+    exp.setSourceFile(sourceFile);
+  }
+
+  public static void setInstance(final BaseExpression exp, AviatorEvaluatorInstance instance) {
+    exp.setInstance(instance);
+  }
+
+  public static void setCompileEnv(final BaseExpression exp, final Env compileEnv) {
+    exp.setCompileEnv(compileEnv);
+  }
+
+  public static void setExpression(final BaseExpression exp, final String expression) {
+    exp.setExpression(expression);
+  }
+
+  public static void setFuncsArgs(final BaseExpression exp,
+      final Map<Integer, List<FunctionArgument>> funcsArgs) {
+    exp.setFuncsArgs(funcsArgs);
+  }
+
+  public static void setLambdaBootstraps(final BaseExpression exp,
+      final Map<String, LambdaFunctionBootstrap> lambdaBootstraps) {
+    exp.setLambdaBootstraps(lambdaBootstraps);
+  }
+
+  public static void setFunctionNames(final BaseExpression exp, List<String> functionNames) {
+    exp.setFunctionNames(functionNames);
+  }
+}
diff --git a/src/main/java/com/googlecode/aviator/code/BaseEvalCodeGenerator.java b/src/main/java/com/googlecode/aviator/code/BaseEvalCodeGenerator.java
index c888f25a..39b1b555 100644
--- a/src/main/java/com/googlecode/aviator/code/BaseEvalCodeGenerator.java
+++ b/src/main/java/com/googlecode/aviator/code/BaseEvalCodeGenerator.java
@@ -43,6 +43,8 @@ public abstract class BaseEvalCodeGenerator implements EvalCodeGenerator {
    */
   protected final Env compileEnv;
 
+  protected Map<String, Integer/* counter */> methodTokens = Collections.emptyMap();
+
   protected Map<Integer/* internal function id */, List<FunctionArgument>> getFuncsArgs() {
     if (this.funcsArgs == null) {
       this.funcsArgs = new HashMap<>();
@@ -54,6 +56,11 @@ protected int getNextFuncInvocationId() {
     return this.funcInvocationId++;
   }
 
+  @Override
+  public void initMethods(Map<String, Integer> methods) {
+    this.methodTokens = methods;
+  }
+
   @Override
   public void setParser(final Parser parser) {
     this.parser = parser;
diff --git a/src/main/java/com/googlecode/aviator/code/OptimizeCodeGenerator.java b/src/main/java/com/googlecode/aviator/code/OptimizeCodeGenerator.java
index b8c93ffb..29ef7f05 100644
--- a/src/main/java/com/googlecode/aviator/code/OptimizeCodeGenerator.java
+++ b/src/main/java/com/googlecode/aviator/code/OptimizeCodeGenerator.java
@@ -28,6 +28,7 @@
 import com.googlecode.aviator.AviatorEvaluatorInstance;
 import com.googlecode.aviator.BaseExpression;
 import com.googlecode.aviator.Expression;
+import com.googlecode.aviator.ExpressionAccessor;
 import com.googlecode.aviator.Feature;
 import com.googlecode.aviator.LiteralExpression;
 import com.googlecode.aviator.exception.CompileExpressionErrorException;
@@ -448,8 +449,8 @@ public Expression getResult(final boolean unboxObject) {
 
 
     if (exp instanceof BaseExpression) {
-      ((BaseExpression) exp).setCompileEnv(getCompileEnv());
-      ((BaseExpression) exp).setSourceFile(this.sourceFile);
+      ExpressionAccessor.setCompileEnv((BaseExpression) exp, getCompileEnv());
+      ExpressionAccessor.setSourceFile((BaseExpression) exp, this.sourceFile);
     }
     return exp;
   }
diff --git a/src/main/java/com/googlecode/aviator/code/asm/ASMCodeGenerator.java b/src/main/java/com/googlecode/aviator/code/asm/ASMCodeGenerator.java
index 49733ebd..de5e5171 100644
--- a/src/main/java/com/googlecode/aviator/code/asm/ASMCodeGenerator.java
+++ b/src/main/java/com/googlecode/aviator/code/asm/ASMCodeGenerator.java
@@ -58,6 +58,7 @@
 import com.googlecode.aviator.AviatorEvaluatorInstance;
 import com.googlecode.aviator.ClassExpression;
 import com.googlecode.aviator.Expression;
+import com.googlecode.aviator.ExpressionAccessor;
 import com.googlecode.aviator.Options;
 import com.googlecode.aviator.asm.ClassWriter;
 import com.googlecode.aviator.asm.Label;
@@ -127,8 +128,6 @@ public class ASMCodeGenerator extends BaseEvalCodeGenerator {
   private Map<Token<?>/* constant token */, String/* field name */> constantPool =
       Collections.emptyMap();
 
-  private Map<String, Integer/* counter */> methodTokens = Collections.emptyMap();
-
   private final Map<Label, Map<String/* inner name */, Integer/* local index */>> labelNameIndexMap =
       new IdentityHashMap<>();
   private static final Label START_LABEL = new Label();
@@ -730,9 +729,10 @@ public Expression getResult(final boolean unboxObject) {
           defineClass.getConstructor(AviatorEvaluatorInstance.class, List.class, SymbolTable.class);
       ClassExpression exp = (ClassExpression) constructor.newInstance(this.instance,
           new ArrayList<VariableMeta>(this.variables.values()), this.symbolTable);
-      exp.setLambdaBootstraps(this.lambdaBootstraps);
-      exp.setFuncsArgs(this.funcsArgs);
-      exp.setSourceFile(this.sourceFile);
+      ExpressionAccessor.setLambdaBootstraps(exp, this.lambdaBootstraps);
+      ExpressionAccessor.setFuncsArgs(exp, this.funcsArgs);
+      ExpressionAccessor.setSourceFile(exp, this.sourceFile);
+      ExpressionAccessor.setFunctionNames(exp, new ArrayList<>(this.methodTokens.keySet()));
       if (enableSerializable) {
         exp.setClassBytes(bytes);
       }
@@ -1048,7 +1048,7 @@ public void initConstants(final Set<Token<?>> constants) {
 
   @Override
   public void initMethods(final Map<String, Integer/* counter */> methods) {
-    this.methodTokens = methods;
+    super.initMethods(methods);
     this.innerMethodMap = new HashMap<>(methods.size());
     for (String outterMethodName : methods.keySet()) {
       // Use inner method name instead of outter method name
diff --git a/src/main/java/com/googlecode/aviator/code/interpreter/InterpretCodeGenerator.java b/src/main/java/com/googlecode/aviator/code/interpreter/InterpretCodeGenerator.java
index d0139f55..e680d500 100644
--- a/src/main/java/com/googlecode/aviator/code/interpreter/InterpretCodeGenerator.java
+++ b/src/main/java/com/googlecode/aviator/code/interpreter/InterpretCodeGenerator.java
@@ -11,6 +11,7 @@
 import java.util.Stack;
 import com.googlecode.aviator.AviatorEvaluatorInstance;
 import com.googlecode.aviator.Expression;
+import com.googlecode.aviator.ExpressionAccessor;
 import com.googlecode.aviator.InterpretExpression;
 import com.googlecode.aviator.Options;
 import com.googlecode.aviator.code.BaseEvalCodeGenerator;
@@ -117,9 +118,6 @@ public void initConstants(final Set<Token<?>> constants) {
     this.constantPool = constants;
   }
 
-  @Override
-  public void initMethods(final Map<String, Integer> methods) {}
-
   @Override
   public void genNewLambdaCode(final LambdaFunctionBootstrap bootstrap) {
     emit(new NewLambdaIR(bootstrap.getName()));
@@ -358,9 +356,10 @@ public Expression getResult(final boolean unboxObject) {
     final InterpretExpression exp =
         new InterpretExpression(this.instance, new ArrayList<VariableMeta>(this.variables.values()),
             this.constantPool, this.symbolTable, instruments, unboxObject);
-    exp.setLambdaBootstraps(this.lambdaBootstraps);
-    exp.setSourceFile(this.sourceFile);
-    exp.setFuncsArgs(this.funcsArgs);
+    ExpressionAccessor.setLambdaBootstraps(exp, this.lambdaBootstraps);
+    ExpressionAccessor.setSourceFile(exp, this.sourceFile);
+    ExpressionAccessor.setFuncsArgs(exp, this.funcsArgs);
+    ExpressionAccessor.setFunctionNames(exp, new ArrayList<String>(this.methodTokens.keySet()));
 
     return exp;
   }
diff --git a/src/main/java/com/googlecode/aviator/parser/ExpressionParser.java b/src/main/java/com/googlecode/aviator/parser/ExpressionParser.java
index fa6e28dd..98ff2327 100644
--- a/src/main/java/com/googlecode/aviator/parser/ExpressionParser.java
+++ b/src/main/java/com/googlecode/aviator/parser/ExpressionParser.java
@@ -437,11 +437,11 @@ public void equality() {
 
           }
 
-          statement();
+          StatementType stmtType = statement();
 
           // try to find var(prevToken) in right statement, it's not initialized if presents.
           if (isVar) {
-            checkVarIsInit(prevToken);
+            checkVarIsInit(prevToken, stmtType);
           }
 
           ensureFeatureEnabled(Feature.Assignment);
@@ -464,7 +464,7 @@ public void equality() {
 
 
 
-  private void checkVarIsInit(final Token<?> prevToken) {
+  private void checkVarIsInit(final Token<?> prevToken, StatementType stmtType) {
     boolean isInit = true;
     for (Token<?> t : this.prevTokens) {
       if (t == prevToken) {
@@ -1262,10 +1262,11 @@ private void letStatement() {
       reportSyntaxError("expect '='");
     }
     move(true);
-    if (statement() == StatementType.Empty) {
+    StatementType stmtType = statement();
+    if (stmtType == StatementType.Empty) {
       reportSyntaxError("invalid value to define");
     }
-    checkVarIsInit(var);
+    checkVarIsInit(var, stmtType);
     ensureFeatureEnabled(Feature.Assignment);
     getCodeGeneratorWithTimes().onAssignment(currentToken().withMeta(Constants.DEFINE_META, true));
     if (!expectChar(';')) {
diff --git a/src/main/java/com/googlecode/aviator/serialize/AviatorObjectInputStream.java b/src/main/java/com/googlecode/aviator/serialize/AviatorObjectInputStream.java
index 9a1816d6..88420363 100644
--- a/src/main/java/com/googlecode/aviator/serialize/AviatorObjectInputStream.java
+++ b/src/main/java/com/googlecode/aviator/serialize/AviatorObjectInputStream.java
@@ -11,6 +11,7 @@
 import com.googlecode.aviator.BaseExpression;
 import com.googlecode.aviator.ClassExpression;
 import com.googlecode.aviator.Expression;
+import com.googlecode.aviator.ExpressionAccessor;
 import com.googlecode.aviator.code.asm.ClassDefiner;
 import com.googlecode.aviator.lexer.SymbolTable;
 import com.googlecode.aviator.lexer.token.Variable;
@@ -82,7 +83,7 @@ protected Object resolveObject(Object obj) throws IOException {
   }
 
   private void configureExpression(BaseExpression exp) {
-    exp.setInstance(this.instance);
+    ExpressionAccessor.setInstance(exp, this.instance);
     if (exp instanceof ClassExpression) {
       ((ClassExpression) exp).setClassBytes(this.classBytesCache.get(exp.getClass().getName()));
     }
diff --git a/src/test/java/com/googlecode/aviator/LambdaUnitTest.java b/src/test/java/com/googlecode/aviator/LambdaUnitTest.java
index dd573985..5a8b3333 100644
--- a/src/test/java/com/googlecode/aviator/LambdaUnitTest.java
+++ b/src/test/java/com/googlecode/aviator/LambdaUnitTest.java
@@ -1,11 +1,15 @@
 package com.googlecode.aviator;
 
 import static com.googlecode.aviator.TestUtils.assertEquals;
+import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertSame;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
+import java.util.Arrays;
+import java.util.Collections;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 import org.junit.Test;
 import com.googlecode.aviator.exception.ExpressionRuntimeException;
@@ -149,4 +153,33 @@ public void testLambdaWithHighOrderFunction() {
     assertEquals(AviatorEvaluator.execute(
         "reduce(filter(a, lambda(x) -> x > 49 end), lambda(r,e) -> r + e end, 0)", env), sum);
   }
+
+  @Test
+  public void testGetFunctionNames() {
+    List<String> names = compileAndGetFuncNames("reduce(a, lambda(r,e) -> r + e end, 0)");
+    assertEquals(Arrays.asList("reduce"), names);
+
+    names = compileAndGetFuncNames(
+        "reduce(filter(a, lambda(x) -> x > 49 end), lambda(r,e) -> r + e end, 0)");
+    assertEquals(Arrays.asList("filter", "reduce"), names);
+
+    names = compileAndGetFuncNames(
+        "let x = lambda(x) -> x > 49 end; reduce(filter(a, x), lambda(r,e) -> r + e end, 0)");
+    assertEquals(Arrays.asList("filter", "reduce"), names);
+
+    names = compileAndGetFuncNames(
+        "let y = lambda(x) -> x > 49 end; y(); reduce(filter(a, y), lambda(r,e) -> r + e end, 0)");
+    assertEquals(Arrays.asList("filter", "reduce"), names);
+
+    names = compileAndGetFuncNames(
+        "let y = fn(x) { x > 49 }; y(); let z = lambda(r,e) -> r + e end; reduce(filter(a, y), z, 0)");
+    assertEquals(Arrays.asList("filter", "reduce"), names);
+  }
+
+  private List<String> compileAndGetFuncNames(String script) {
+    Expression exp = AviatorEvaluator.compile(script);
+    List<String> names = exp.getFunctionNames();
+    Collections.sort(names);
+    return names;
+  }
 }
diff --git a/src/test/java/com/googlecode/aviator/scripts/TestScripts.java b/src/test/java/com/googlecode/aviator/scripts/TestScripts.java
index 092a987e..f3f2ab1d 100644
--- a/src/test/java/com/googlecode/aviator/scripts/TestScripts.java
+++ b/src/test/java/com/googlecode/aviator/scripts/TestScripts.java
@@ -93,6 +93,13 @@ public Object testLib(final String name, final Object... args) {
     return null;
   }
 
+  @Test
+  public void testGetFunctionNames() throws Exception {
+    final String file = TestScripts.class.getResource("/scripts/qsort.av").getFile();
+    Expression exp = this.instance.compileScript(file, true);
+    assertEquals(Arrays.asList("count"), exp.getFunctionNames());
+  }
+
   @Test
   public void testLibs() {
     testLib("aviator");
diff --git a/src/test/java/com/googlecode/aviator/test/function/FunctionTest.java b/src/test/java/com/googlecode/aviator/test/function/FunctionTest.java
index 2f16f397..2c88f597 100644
--- a/src/test/java/com/googlecode/aviator/test/function/FunctionTest.java
+++ b/src/test/java/com/googlecode/aviator/test/function/FunctionTest.java
@@ -26,6 +26,7 @@
 import java.math.BigInteger;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.Date;
 import java.util.HashMap;
 import java.util.HashSet;
@@ -746,58 +747,71 @@ public void run() {
   }
 
   @Test
-  public void testGetVariableNamesComplex() {
+  public void testGetVariableNamesAndFunctionNamesComplex() {
     // lambda
     Expression exp = this.instance.compile("a = 1; add = lambda(x) -> x + a end; add(b)");
     List<String> vars = exp.getVariableNames();
-    System.out.println(vars);
+    List<String> funcs = getFuncs(exp);
     assertEquals(1, vars.size());
-
     assertEquals("b", vars.get(0));
+    assertEquals(0, funcs.size());
 
     // lambda closure over
     exp = this.instance.compile("add = lambda(x) -> x + a end; add(b)");
     vars = exp.getVariableNames();
+    funcs = getFuncs(exp);
     assertEquals(2, vars.size());
     assertEquals("a", vars.get(0));
     assertEquals("b", vars.get(1));
+    assertEquals(0, funcs.size());
 
     // if.. else
     exp = this.instance
         .compile("b=2; if(a > 1) { a + b } elsif( a > 10) { return a + c; } else { return 10; }");
     vars = exp.getVariableNames();
+    funcs = getFuncs(exp);
     assertEquals(2, vars.size());
     assertEquals("a", vars.get(0));
     assertEquals("c", vars.get(1));
+    assertEquals(0, funcs.size());
 
     // for..loop
     exp = this.instance
         .compile("let list = seq.list(1, 2, 3); for x in list { sum = sum + x }; return sum;");
     vars = exp.getVariableNames();
+    funcs = getFuncs(exp);
     assertEquals(1, vars.size());
     assertEquals("sum", vars.get(0));
+    assertEquals(1, funcs.size());
+    assertEquals(Arrays.asList("seq.list"), funcs);
 
     // let statement in block
     exp = this.instance.compile("{let a = 1; let b = b + 1; p(a+b);} c-a");
+    funcs = getFuncs(exp);
     vars = exp.getVariableNames();
     assertEquals(3, vars.size());
     assertEquals("b", vars.get(0));
     assertEquals("c", vars.get(1));
     assertEquals("a", vars.get(2));
+    assertEquals(Arrays.asList("p"), funcs);
 
     // redfine variable
     exp = this.instance.compile("{let a = 1; let b = 2; let b = b + 1; p(a+b);} c-a");
     vars = exp.getVariableNames();
+    funcs = getFuncs(exp);
     assertEquals(2, vars.size());
     assertEquals("c", vars.get(0));
     assertEquals("a", vars.get(1));
+    assertEquals(Arrays.asList("p"), funcs);
 
     // high-order function
     exp = this.instance.compile("map(list, lambda(v) -> v + u end)");
     vars = exp.getVariableNames();
+    funcs = getFuncs(exp);
     assertEquals(2, vars.size());
     assertEquals("list", vars.get(0));
     assertEquals("u", vars.get(1));
+    assertEquals(Arrays.asList("map"), funcs);
 
     // a complex script
     exp = this.instance.compile("let n = 0;  let index =0 ; " + "for i in a {"
@@ -805,25 +819,37 @@ public void testGetVariableNamesComplex() {
         + "let m = date.month(b, i); " + "if c[index] == '03' && m <= 12 {" + " n = n + 1; " + "}"
         + "index = index + 1;" + "  } return n;");
     vars = exp.getVariableNames();
+    funcs = getFuncs(exp);
     assertEquals(3, vars.size());
     assertEquals("a", vars.get(0));
     assertEquals("b", vars.get(1));
     assertEquals("c", vars.get(2));
+    assertEquals(Arrays.asList("date.month", "string_to_date"), funcs);
 
     exp = this.instance.compile("a = seq.map(); add = lambda() -> a.b + a.c end; add()");
     vars = exp.getVariableNames();
+    funcs = getFuncs(exp);
     assertEquals(0, vars.size());
     vars = exp.getVariableFullNames();
     assertEquals(2, vars.size());
     assertEquals("a.b", vars.get(0));
     assertEquals("a.c", vars.get(1));
+    assertEquals(Arrays.asList("seq.map"), funcs);
 
     exp = this.instance.compile("a = seq.map(); a.c = 2; add = lambda() -> a.b + a.c end; add()");
+    funcs = getFuncs(exp);
     vars = exp.getVariableNames();
     assertEquals(0, vars.size());
     vars = exp.getVariableFullNames();
     assertEquals(1, vars.size());
     assertEquals("a.b", vars.get(0));
+    assertEquals(Arrays.asList("seq.map"), funcs);
+  }
+
+  private List<String> getFuncs(Expression exp) {
+    List<String> funcs = exp.getFunctionNames();
+    Collections.sort(funcs);
+    return funcs;
   }
 
   @Test