diff -r 217123f59d7e -r bf6d7b624d5c lemon/random.h
--- a/lemon/random.h	Mon Oct 01 18:55:58 2007 +0000
+++ b/lemon/random.h	Mon Oct 01 18:57:21 2007 +0000
@@ -748,6 +748,44 @@
       return -std::log(real<double>())/lambda;
     }
 
+    double gamma(int k) 
+    {
+      double s = 0;
+      for(int i=0;i<k;i++) s-=std::log(1.0-real<double>());
+      return s;
+    }
+    
+    /// Gamma distribution with given shape and scale parameter
+
+    /// This function generates a gamma distribution random number.
+    /// 
+    ///\param k shape parameter (<tt>k>0</tt>)
+    ///\param theta scale parameter
+    ///
+    double gamma(double k,double theta=1.0)
+    {
+      double xi,nu;
+      const double delta = k-std::floor(k);
+      const double v0=M_E/(M_E-delta);
+      do {
+	double V0=1.0-real<double>();
+	double V1=1.0-real<double>();
+	double V2=1.0-real<double>();
+	if(V2<=v0) 
+	  {
+	    xi=std::pow(V1,1.0/delta);
+	    nu=V0*std::pow(xi,delta-1.0);
+	  }
+	else 
+	  {
+	    xi=1.0-std::log(V1);
+	    nu=V0*std::exp(-xi);
+	  }
+      } while(nu>std::pow(xi,delta-1.0)*std::exp(-xi));
+      return theta*(xi-gamma(int(std::floor(k))));
+    }
+    
+      
     ///@}
     
     ///\name Two dimensional distributions