diff -r 88efddb08ce6 src/core/random-variable.cc
--- a/src/core/random-variable.cc	Fri Mar 20 12:28:21 2009 -0400
+++ b/src/core/random-variable.cc	Tue May 26 16:58:15 2009 +0200
@@ -1291,6 +1291,70 @@
   : RandomVariable (TriangularVariableImpl (s,l,mean))
 {}
 
+//-----------------------------------------------------------------------------
+//-----------------------------------------------------------------------------
+// ZipfVariableImpl
+class ZipfVariableImpl : public RandomVariableBase { 
+public:
+  /**
+   * \param n the number of possible items
+   * \param alpha the alpha parameter
+   */
+  ZipfVariableImpl (long n, double alpha);
+
+  /**
+   * \return A random value from this distribution
+   */
+  virtual double GetValue ();
+  virtual RandomVariableBase* Copy(void) const;
+
+private:
+  long m_n;
+  double m_alpha;
+  double m_c; //the normalization constant
+};
+
+
+RandomVariableBase* ZipfVariableImpl::Copy () const
+{
+  return new ZipfVariableImpl (m_n, m_alpha);
+}
+
+ZipfVariableImpl::ZipfVariableImpl (long n, double alpha)
+    :m_n(n), m_alpha(alpha), m_c(0)
+{
+  //calculate the normalization constant c
+  for(int i=1;i<=n;i++)
+    m_c+=(1.0/pow((double)i,alpha));
+  m_c=1.0/m_c;
+}
+
+double
+ZipfVariableImpl::GetValue ()
+{
+  if(!m_generator)
+  {
+    m_generator = new RngStream();
+  }
+
+  double u = m_generator->RandU01();
+  double sum_prob=0,zipf_value;
+  for(int i=1;i<=m_n;i++)
+  {
+    sum_prob+=m_c/pow((double)i,m_alpha);
+    if(sum_prob>u)
+    {
+      zipf_value=i;
+      break;
+    }
+  }
+  return zipf_value;
+}
+
+ZipfVariable::ZipfVariable (long n, double alpha)
+  : RandomVariable (ZipfVariableImpl (n, alpha))
+{}
+
 
 std::ostream &operator << (std::ostream &os, const RandomVariable &var)
 {
diff -r 88efddb08ce6 src/core/random-variable.h
--- a/src/core/random-variable.h	Fri Mar 20 12:28:21 2009 -0400
+++ b/src/core/random-variable.h	Tue May 26 16:58:15 2009 +0200
@@ -594,6 +594,21 @@
 };
 
 /**
+ * \brief Zipf Distributed random var
+ * \ingroup randomvariable
+ *
+ */
+class ZipfVariable : public RandomVariable 
+{
+public:
+  /**
+   * \param n the number of possible items
+   * \param alpha the alpha parameter
+   */
+  ZipfVariable (long n, double alpha);
+};
+
+/**
  * \brief Triangularly Distributed random var
  * \ingroup randomvariable
  *