* eval.c (eval_init): Register last function as intrinsic.

* lib.c (last): New function.

* lib.h (last): Declared.

* txr.1: Documented last.

5 files changed, 34 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index 693c5d27..2ee31328 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,15 @@
 2014-03-23  Kaz Kylheku  <kaz@kylheku.com>
 
+	* eval.c (eval_init): Register last function as intrinsic.
+
+	* lib.c (last): New function.
+
+	* lib.h (last): Declared.
+
+	* txr.1: Documented last.
+
+2014-03-23  Kaz Kylheku  <kaz@kylheku.com>
+
 	* eval.c (eval_init): Register empty as intrinsic.
 
 	* lib.c (copy): Bugfix: handle lazy strings. Also, handle hash
diff --git a/eval.c b/eval.c
index 8e70ec29..c502800f 100644
--- a/eval.c
+++ b/eval.c
@@ -3257,6 +3257,7 @@ void eval_init(void)
   reg_fun(intern(lit("nreverse"), user_package), func_n1(nreverse));
   reg_fun(intern(lit("reverse"), user_package), func_n1(reverse));
   reg_fun(intern(lit("ldiff"), user_package), func_n2(ldiff));
+  reg_fun(intern(lit("last"), user_package), func_n1(last));
   reg_fun(intern(lit("flatten"), user_package), func_n1(flatten));
   reg_fun(intern(lit("flatten*"), user_package), func_n1(lazy_flatten));
   reg_fun(intern(lit("memq"), user_package), func_n2(memq));
diff --git a/lib.c b/lib.c
index 505ae3e6..def54e2f 100644
--- a/lib.c
+++ b/lib.c
@@ -412,6 +412,12 @@ val *lastcons(val list)
   return ret;
 }
 
+val last(val list)
+{
+  val *p = lastcons(list);
+  return p ? *p : list;
+}
+
 val *ltail(val *cons)
 {
   while (cdr(*cons))
diff --git a/lib.h b/lib.h
index b48bf39f..702ef585 100644
--- a/lib.h
+++ b/lib.h
@@ -392,6 +392,7 @@ val listref(val list, val ind);
 val *listref_l(val list, val ind);
 val *tail(val cons);
 val *lastcons(val list);
+val last(val list);
 val *ltail(val *cons);
 val pop(val *plist);
 val upop(val *plist, val *pundo);
diff --git a/txr.1 b/txr.1
index 60906447..defd6a17 100644
--- a/txr.1
+++ b/txr.1
@@ -7353,6 +7353,22 @@ Examples:
     (ldiff a b))
   -> (1)
 
+.SS Function last
+
+.TP
+Syntax:
+
+  (last <list>)
+
+.TP
+Description:
+
+If <list> is a nonempty proper or improper list, the last function
+returns the last cons cell in the list: that cons cell whose cdr field
+is a terminating atom.
+
+If <list> is nil, then nil is returned.
+
 .SS Functions flatten, flatten*
 
 .TP