1:
$cppawk '
#include <array.h>

BEGIN {
  $0 = "1 2 3 4"
  fields_to_array(a)

  for (i in a)
    count++

  print "count =", count

  for (i = 1; i <= 4; i++)
    printf "a[%s] = %s\n", i, a[i]

  print "a[0] =", a[0]
}'
:
count = 5
a[1] = 1
a[2] = 2
a[3] = 3
a[4] = 4
a[0] = 1 2 3 4
--
2:
$cppawk '
#include <array.h>

BEGIN {
  fields_to_array(a)

  count = 0
  for (i in a)
    count++

  print "count =", count
  print "a[0] =", a[0]
}'
:
count = 1
a[0] = 
--
3:
$cppawk '
#include <array.h>
BEGIN {
  x = fun(cos)
}
:
ERR
--
4:
$cppawk '
#include <array.h>

BEGIN {
  a[0] = "foo"
  for (i = 1; i <= 10; i++)
     a[i] = i
  delete a[7]
  array_to_fields(a)
  print
}'
:
1 2 3 4 5 6
--
5:
$cppawk '
#include <array.h>
#include <cons.h>
#include <fun.h>

function even(x)
{
   return x % 2 == 0
}

BEGIN {
  group_by(fun(even), iota(1, 10), a)
  print sexp(a[0]);
  print sexp(a[1]);
}'
:
(1 3 5 7 9)
(2 4 6 8 10)
--
6:
$cppawk '
#include <array.h>
#include <cons.h>
#include <fun.h>

function even(x)
{
   return x % 2 == 0
}

BEGIN {
  group_by(fun(even), iota(1, 10), a)
  maparray(fun(reverse), a, b)
  print sexp(b[0])
  print sexp(b[1])
}'
:
(9 7 5 3 1)
(10 8 6 4 2)