Implementing second through tenth as places.

* eval.c (eval_init): Register second through tenth as intrinsic.

* gencadr.txr: New cadr.c changes encoded.

* lib.c (second, third, fourth, fifth, sixth): Functions
reimplemented using ref, so they are much more efficient
for vectors and strings.
(seventh, eighth, ninth, tenth): New functions.

* lib.h (seventh, eighth, ninth, tenth): Declared.

* share/txr/stdlib/place.tl: place macros defined for
second through tenth.

* txr.1: Documented.

6 files changed, 96 insertions, 22 deletions

diff --git a/ChangeLog b/ChangeLog
index 76f963d5..d73ad31d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,25 @@
 2015-07-22  Kaz Kylheku  <kaz@kylheku.com>
 
+	Implementing second through tenth as places.
+
+	* eval.c (eval_init): Register second through tenth as intrinsic.
+
+	* gencadr.txr: New cadr.c changes encoded.
+
+	* lib.c (second, third, fourth, fifth, sixth): Functions
+	reimplemented using ref, so they are much more efficient
+	for vectors and strings.
+	(seventh, eighth, ninth, tenth): New functions.
+
+	* lib.h (seventh, eighth, ninth, tenth): Declared.
+
+	* share/txr/stdlib/place.tl: place macros defined for
+	second through tenth.
+
+	* txr.1: Documented.
+
+2015-07-22  Kaz Kylheku  <kaz@kylheku.com>
+
 	* lisplib.c (place_set_entries): Add *place-macro* and
 	define-place-macro to list of names.
 
diff --git a/eval.c b/eval.c
index e0ef15a8..0a9e89de 100644
--- a/eval.c
+++ b/eval.c
@@ -4140,6 +4140,10 @@ void eval_init(void)
   reg_fun(intern(lit("fourth"), user_package), func_n1(fourth));
   reg_fun(intern(lit("fifth"), user_package), func_n1(fifth));
   reg_fun(intern(lit("sixth"), user_package), func_n1(sixth));
+  reg_fun(intern(lit("seventh"), user_package), func_n1(seventh));
+  reg_fun(intern(lit("eighth"), user_package), func_n1(eighth));
+  reg_fun(intern(lit("ninth"), user_package), func_n1(ninth));
+  reg_fun(intern(lit("tenth"), user_package), func_n1(tenth));
   reg_fun(intern(lit("conses"), user_package), func_n1(conses));
   reg_fun(intern(lit("conses*"), user_package), func_n1(lazy_conses));
   reg_fun(intern(lit("copy-list"), user_package), func_n1(copy_list));
diff --git a/lib.c b/lib.c
index 9bcce5e4..4d0c901b 100644
--- a/lib.c
+++ b/lib.c
@@ -367,29 +367,49 @@ val rest(val cons)
   return cdr(cons);
 }
 
-val second(val cons)
+val second(val obj)
 {
-  return car(cdr(cons));
+  return ref(obj, one);
 }
 
-val third(val cons)
+val third(val obj)
 {
-  return car(cdr(cdr(cons)));
+  return ref(obj, two);
 }
 
-val fourth(val cons)
+val fourth(val obj)
 {
-  return car(cdr(cdr(cdr(cons))));
+  return ref(obj, three);
 }
 
-val fifth(val cons)
+val fifth(val obj)
 {
-  return car(cdr(cdr(cdr(cdr(cons)))));
+  return ref(obj, four);
 }
 
-val sixth(val cons)
+val sixth(val obj)
 {
-  return car(cdr(cdr(cdr(cdr(cdr(cons))))));
+  return ref(obj, num_fast(5));
+}
+
+val seventh(val obj)
+{
+  return ref(obj, num_fast(6));
+}
+
+val eighth(val obj)
+{
+  return ref(obj, num_fast(7));
+}
+
+val ninth(val obj)
+{
+  return ref(obj, num_fast(8));
+}
+
+val tenth(val obj)
+{
+  return ref(obj, num_fast(9));
 }
 
 val conses(val list)
diff --git a/lib.h b/lib.h
index 9ffdcbc5..7a37030a 100644
--- a/lib.h
+++ b/lib.h
@@ -445,6 +445,10 @@ val third(val cons);
 val fourth(val cons);
 val fifth(val cons);
 val sixth(val cons);
+val seventh(val cons);
+val eighth(val cons);
+val ninth(val cons);
+val tenth(val cons);
 val conses(val list);
 val lazy_conses(val list);
 val listref(val list, val ind);
diff --git a/share/txr/stdlib/place.tl b/share/txr/stdlib/place.tl
index 0356e81e..67a593fb 100644
--- a/share/txr/stdlib/place.tl
+++ b/share/txr/stdlib/place.tl
@@ -614,3 +614,12 @@
 
 (define-place-macro first (obj) ^(car ,obj))
 (define-place-macro rest (obj) ^(cdr ,obj))
+(define-place-macro second (obj) ^(ref ,obj 1))
+(define-place-macro third (obj) ^(ref ,obj 2))
+(define-place-macro fourth (obj) ^(ref ,obj 3))
+(define-place-macro fifth (obj) ^(ref ,obj 4))
+(define-place-macro sixth (obj) ^(ref ,obj 5))
+(define-place-macro seventh (obj) ^(ref ,obj 6))
+(define-place-macro eighth (obj) ^(ref ,obj 7))
+(define-place-macro ninth (obj) ^(ref ,obj 8))
+(define-place-macro tenth (obj) ^(ref ,obj 9))
diff --git a/txr.1 b/txr.1
index b6b952a8..53b90055 100644
--- a/txr.1
+++ b/txr.1
@@ -13713,26 +13713,43 @@ specifies the contents of the entire string or vector, as if the operation
 were done on a non-empty vector or string, followed by the deletion of the
 first element.
 
-.coNP Functions @, second @, third @, fourth @ fifth and @ sixth
+.coNP Accessors @, second @, third @, fourth @, fifth @, sixth @, seventh @, eighth @ ninth and @ tenth
 .synb
-.mets (first << list )
-.mets (second << list )
-.mets (third << list )
-.mets (fourth << list )
-.mets (fifth << list )
-.mets (sixth << list )
+.mets (first << object )
+.mets (second << object )
+.mets (third << object )
+.mets (fourth << object )
+.mets (fifth << object )
+.mets (sixth << object )
+.mets (seventh << object )
+.mets (eighth << object )
+.mets (ninth << object )
+.mets (tenth << object )
+.mets (set (first << object ) << new-value )
+.mets (set (second << object ) << new-value )
+.mets ...
+.mets (set (tenth << object ) << new-value )
 .syne
 .desc
-These functions access the elements of a proper list by position.
-
-If the list is shorter than implied, these functions return
+Used as functions, these accessors retrieve the elements of a sequence by
+position.  If the sequence is shorter than implied by the position, these
+functions return
 .codn nil .
 
+When used as syntactic places, these accessors denote the storage locations
+by position. The location must exist, otherwise an error exception results.
+The places support deletion.
+
+
 .TP* Examples:
 .cblk
   (third '(1 2)) -> nil
-  (second '(1 2)) -> 2
-  (third '(1 2 . 3)) -> **error**
+  (second "ab") -> #\eb
+  (third '(1 2 . 3)) -> **error, improper list*
+
+  (let ((x (copy "abcd")))
+    (inc (third x))
+    x) -> "abce"
 .cble
 
 .coNP Functions @, append @ nconc and @ append*