list: new operations: head and tail.

* include/mailutils/list.h (mu_list_head, mu_list_tail): New prototypes.
* libmailutils/list/head.c: New file.
* libmailutils/list/tail.c: New file.
* libmailutils/list/Makefile.am (liblist_la_SOURCES): Add new files.
* libmailutils/tests/listop.c (head,tail): New commands.
* libmailutils/tests/list.at: Test head and tail.

@@ -86,6 +86,11 @@ int mu_list_count    (mu_list_t _list, size_t *_pcount);
   
   /* Get _indexth element from the list and store it in _pitem. */
 int mu_list_get      (mu_list_t _list, size_t _index, void **_pitem);
+  /* Retrieve first element of _list */
+int mu_list_head (mu_list_t _list, void **_pitem);
+  /* Retrieve last element of _list */
+int mu_list_tail (mu_list_t _list, void **_pitem);
+  
   /* Store at most _count first elements from _list in the _array.  Unless
      _pcount is NULL, fill it with the actual number of elements copied. */
 int mu_list_to_array (mu_list_t _list, void **_array, size_t _count,

@@ -29,6 +29,7 @@ liblist_la_SOURCES = \
  get.c\
  getcomp.c\
  gmap.c\
+ head.c\
  insert.c\
  intersect.c\
  iterator.c\
@@ -41,7 +42,8 @@ liblist_la_SOURCES = \
  setcomp.c\
  setdestr.c\
  slice.c\
- slice2.c
+ slice2.c\
+ tail.c
 
 INCLUDES = @MU_LIB_COMMON_INCLUDES@ -I/libmailutils
 

+/* GNU Mailutils -- a suite of utilities for electronic mail
+   Copyright (C) 2011 Free Software Foundation, Inc.
+
+   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 3 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 library.  If not, see 
+   <http://www.gnu.org/licenses/>. */
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+#include <stdlib.h>
+#include <mailutils/sys/list.h>
+#include <mailutils/errno.h>
+
+int
+mu_list_head (mu_list_t list, void **pitem)
+{
+  if (list == NULL)
+    return EINVAL;
+  if (pitem == NULL)
+    return MU_ERR_OUT_PTR_NULL;
+  if (!list->head.next)
+    return MU_ERR_NOENT;
+  *pitem = list->head.next->item;
+  return 0;
+}

+/* GNU Mailutils -- a suite of utilities for electronic mail
+   Copyright (C) 2011 Free Software Foundation, Inc.
+
+   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 3 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 library.  If not, see 
+   <http://www.gnu.org/licenses/>. */
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+#include <stdlib.h>
+#include <mailutils/sys/list.h>
+#include <mailutils/errno.h>
+
+int
+mu_list_tail (mu_list_t list, void **pitem)
+{
+  if (list == NULL)
+    return EINVAL;
+  if (pitem == NULL)
+    return MU_ERR_OUT_PTR_NULL;
+  if (!list->head.prev)
+    return MU_ERR_NOENT;
+  *pitem = list->head.prev->item;
+  return 0;
+}

@@ -103,6 +103,18 @@ TESTLIST([get],[],
 [fire
 ])
 
+TESTLIST([head],[],
+[add en to tre fire fem
+head],
+[en
+])
+
+TESTLIST([tail],[],
+[add en to tre fire fem
+tail],
+[fem
+])
+
 
 # ------------------------------------------------------------
 # Iterators

@@ -685,6 +685,42 @@ slice (mu_list_t *plist, int argc, char **argv)
 }
 
 void
+head (size_t argc, mu_list_t list)
+{
+  int rc;
+  const char *text;
+    
+  if (argc != 1)
+    {
+      fprintf (stderr, "head ?\n");
+      return;
+    }
+  rc = mu_list_head (list, (void**) &text);
+  if (rc)
+    mu_diag_funcall (MU_DIAG_ERROR, "mu_list_head", NULL, rc);
+  else
+    printf ("%s\n", text);
+}
+
+void
+tail (size_t argc, mu_list_t list)
+{
+  int rc;
+  const char *text;
+    
+  if (argc != 1)
+    {
+      fprintf (stderr, "head ?\n");
+      return;
+    }
+  rc = mu_list_tail (list, (void**) &text);
+  if (rc)
+    mu_diag_funcall (MU_DIAG_ERROR, "mu_list_tail", NULL, rc);
+  else
+    printf ("%s\n", text);
+}
+
+void
 help ()
 {
   printf ("count\n");
@@ -708,6 +744,8 @@ help ()
   printf ("quit\n");
   printf ("iter num\n");
   printf ("help\n");
+  printf ("head\n");
+  printf ("tail\n");
   printf ("NUMBER\n");
 }
 
@@ -819,6 +857,10 @@ shell (mu_list_t list)
 	    find (itr[num], ws.ws_wordv[1]);
 	  else if (strcmp (ws.ws_wordv[0], "help") == 0)
 	    help ();
+	  else if (strcmp (ws.ws_wordv[0], "head") == 0)
+	    head (ws.ws_wordc, list);
+	  else if (strcmp (ws.ws_wordv[0], "tail") == 0)
+	    tail (ws.ws_wordc, list);
 	  else if (ws.ws_wordc == 1)
 	    {
 	      char *p;