1:
$cppawk '
#include <cons.h>
#include <field.h>

#define pf {print sexp(fields())}

BEGIN {
  $0 = ""
  delf(1, 0)
  pf
  delf(1, 5)
  pf
  delf(3, 5)
  pf
}'
:
nil
nil
nil
--
2:
$cppawk '
#include <cons.h>
#include <field.h>

#define pf {print sexp(fields())}

BEGIN {
  $0 = "1 2 3 4"
  delf(1, 1)
  pf
  delf(2, 1)
  pf
  delf(3, 0)
  pf
  delf(0, 0)
  pf
  delf(1, 2)
  pf
}'
:
(2 3 4)
(2 4)
(2 4)
(2 4)
nil
--
3:
$cppawk '
#include <cons.h>
#include <field.h>

#define pf {print sexp(fields())}

BEGIN {
  $0 = "1 2 3 4 5"
  delf(1)
  pf
  delf(1)
  pf
  delf(1, 10)
  pf
}'
:
(2 3 4 5)
(3 4 5)
nil
--
4:
$cppawk '
#include <cons.h>
#include <field.h>

#define pf {print sexp(fields())}

BEGIN {
  $0 = "1 2 3 4 5"
  delf(5)
  pf
  delf(4)
  pf
  delf(3, 15)
  pf
  delf(2, 1000)
  pf
  delf(1)
  pf
}'
:
(1 2 3 4)
(1 2 3)
(1 2)
(1)
nil
--
5:
$cppawk '
#include <cons.h>
#include <field.h>

#define pf {print sexp(fields())}

BEGIN {
  $0 = "1 2 3 4 5"
  delf(4, 13)
  pf
}'
:
(1 2 3)
--
6:
$cppawk '
#include <cons.h>
#include <field.h>

#define pf {print sexp(fields())}

BEGIN {
  $0 = "1 2 3 4 5"
  delf(2, 3)
  pf
}'
:
(1 5)
--
7:
$cppawk '
#include <cons.h>
#include <field.h>

#define pf {print sexp(fields())}

BEGIN {
  $0 = ""
  insf(1, 1)
  pf
  insf(2, 2)
  pf
  insf(3, 3)
  pf
  insf(4, 4, 5, 6)
  pf
}'
:
(1)
(1 2)
(1 2 3)
(1 2 3 4 5 6)
--
8:
$cppawk '
#include <cons.h>
#include <field.h>

#define pf {print sexp(fields())}

BEGIN {
  $0 = ""
  insf(3, 3, 4)
  pf
  insf(5, 5, 6)
  pf
  insf(9, 9)
  pf
  insf(0, 1, 2, 3)
  pf
  insf(1, 1, 2)
  pf
}'
:
(nil nil 3 4)
(nil nil 3 4 5 6)
(nil nil 3 4 5 6 nil nil 9)
(nil nil 3 4 5 6 nil nil 9)
(1 2 nil nil 3 4 5 6 nil nil 9)