=== modified file 'pmt/src/lib/pmt.cc'
--- pmt/src/lib/pmt.cc	2009-01-30 14:41:35 +0000
+++ pmt/src/lib/pmt.cc	2009-01-30 16:13:12 +0000
@@ -938,43 +938,43 @@
 }
 
 pmt_t
-pmt_list1(pmt_t x1)
+pmt_list1(const pmt_t& x1)
 {
   return pmt_cons(x1, PMT_NIL);
 }
 
 pmt_t
-pmt_list2(pmt_t x1, pmt_t x2)
+pmt_list2(const pmt_t& x1, const pmt_t& x2)
 {
   return pmt_cons(x1, pmt_cons(x2, PMT_NIL));
 }
 
 pmt_t
-pmt_list3(pmt_t x1, pmt_t x2, pmt_t x3)
+pmt_list3(const pmt_t& x1, const pmt_t& x2, const pmt_t& x3)
 {
   return pmt_cons(x1, pmt_cons(x2, pmt_cons(x3, PMT_NIL)));
 }
 
 pmt_t
-pmt_list4(pmt_t x1, pmt_t x2, pmt_t x3, pmt_t x4)
+pmt_list4(const pmt_t& x1, const pmt_t& x2, const pmt_t& x3, const pmt_t& x4)
 {
   return pmt_cons(x1, pmt_cons(x2, pmt_cons(x3, pmt_cons(x4, PMT_NIL))));
 }
 
 pmt_t
-pmt_list5(pmt_t x1, pmt_t x2, pmt_t x3, pmt_t x4, pmt_t x5)
+pmt_list5(const pmt_t& x1, const pmt_t& x2, const pmt_t& x3, const pmt_t& x4, const pmt_t& x5)
 {
   return pmt_cons(x1, pmt_cons(x2, pmt_cons(x3, pmt_cons(x4, pmt_cons(x5, PMT_NIL)))));
 }
 
 pmt_t
-pmt_list6(pmt_t x1, pmt_t x2, pmt_t x3, pmt_t x4, pmt_t x5, pmt_t x6)
+pmt_list6(const pmt_t& x1, const pmt_t& x2, const pmt_t& x3, const pmt_t& x4, const pmt_t& x5, const pmt_t& x6)
 {
   return pmt_cons(x1, pmt_cons(x2, pmt_cons(x3, pmt_cons(x4, pmt_cons(x5, pmt_cons(x6, PMT_NIL))))));
 }
 
 pmt_t
-pmt_list_add(pmt_t list, pmt_t item)
+pmt_list_add(pmt_t list, const pmt_t& item)
 {
   return pmt_reverse(pmt_cons(item, pmt_reverse(list)));
 }

=== modified file 'pmt/src/lib/pmt.h'
--- pmt/src/lib/pmt.h	2009-01-30 14:41:35 +0000
+++ pmt/src/lib/pmt.h	2009-01-30 16:13:12 +0000
@@ -583,38 +583,38 @@
 /*!
  * \brief Return a list of length 1 containing \p x1
  */
-pmt_t pmt_list1(pmt_t x1);
+pmt_t pmt_list1(const pmt_t& x1);
 
 /*!
  * \brief Return a list of length 2 containing \p x1, \p x2
  */
-pmt_t pmt_list2(pmt_t x1, pmt_t x2);
+pmt_t pmt_list2(const pmt_t& x1, const pmt_t& x2);
 
 /*!
  * \brief Return a list of length 3 containing \p x1, \p x2, \p x3
  */
-pmt_t pmt_list3(pmt_t x1, pmt_t x2, pmt_t x3);
+pmt_t pmt_list3(const pmt_t& x1, const pmt_t& x2, const pmt_t& x3);
 
 /*!
  * \brief Return a list of length 4 containing \p x1, \p x2, \p x3, \p x4
  */
-pmt_t pmt_list4(pmt_t x1, pmt_t x2, pmt_t x3, pmt_t x4);
+pmt_t pmt_list4(const pmt_t& x1, const pmt_t& x2, const pmt_t& x3, const pmt_t& x4);
 
 /*!
  * \brief Return a list of length 5 containing \p x1, \p x2, \p x3, \p x4, \p x5
  */
-pmt_t pmt_list5(pmt_t x1, pmt_t x2, pmt_t x3, pmt_t x4, pmt_t x5);
+pmt_t pmt_list5(const pmt_t& x1, const pmt_t& x2, const pmt_t& x3, const pmt_t& x4, const pmt_t& x5);
 
 /*!
  * \brief Return a list of length 6 containing \p x1, \p x2, \p x3, \p x4, \p
  * x5, \p x6
  */
-pmt_t pmt_list6(pmt_t x1, pmt_t x2, pmt_t x3, pmt_t x4, pmt_t x5, pmt_t x6);
+pmt_t pmt_list6(const pmt_t& x1, const pmt_t& x2, const pmt_t& x3, const pmt_t& x4, const pmt_t& x5, const pmt_t& x6);
 
 /*!
  * \brief Return \p list with \p item added to it.
  */
-pmt_t pmt_list_add(pmt_t list, pmt_t item);
+pmt_t pmt_list_add(pmt_t list, const pmt_t& item);
 
 
 /*