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

BEGIN {
  split("a b c d e f", a)

  doarray (i, v, a)
    print i, v
}'
:
1 a
2 b
3 c
4 d
5 e
6 f
--
2:
$cppawk '
#include <iter.h>

BEGIN {
  doarray (i, v, a)
    print i, v
}'
:
--
3:
$cppawk '
#include <iter.h>

BEGIN {
  $0 = "a b c d e"
  dofields (i, v)
    print i, v
}'
:
1 a
2 b
3 c
4 d
5 e
--
4:
$cppawk '
#include <iter.h>

BEGIN {
  dostring (i, c, 123.0) {
    print i, c
  }
}'
:
1 1
2 2
3 3
--
5:
$cppawk '
#include <iter.h>
BEGIN {
  dostring (i, c, "");
}'
:
--
6:
$cppawk '
#include <iter.h>

BEGIN {
  $0 = "o p q r s t u v w x y z" # set fields

  split("! @ # $ % ^ & * (", arr) # init array

  loop (range(i, 1, 9),
        from(x, 5),
        from_step(y, 100, 5),
        str(j, ch, "abcdefghijklmn"),
        fields(f),
        keys(k, arr))
  {
     print i, x, y, ch, f, k, arr[k]
  }
}'
:
1 5 100 a o 1 !
2 6 105 b p 2 @
3 7 110 c q 3 #
4 8 115 d r 4 $
5 9 120 e s 5 %
6 10 125 f t 6 ^
7 11 130 g u 7 &
8 12 135 h v 8 *
9 13 140 i w 9 (
--
7:
$cppawk '
#include <iter.h>

BEGIN {
  $0 = "a b c" # set fields

  split("X Y", arr) # init array

  loop_nest (fields(f),
             keys(k, arr),
             range(i, 1, 3))
  {
     print f, arr[k], i
  }
}'
:
a X 1
a X 2
a X 3
a Y 1
a Y 2
a Y 3
b X 1
b X 2
b X 3
b Y 1
b Y 2
b Y 3
c X 1
c X 2
c X 3
c Y 1
c Y 2
c Y 3
--
8:
$cppawk '
#include <iter.h>

#define __init_let(var, expr) 1
#define __test_let(var, expr) (var = (expr))
#define __prep_let(var, expr) 1
#define __fini_let(var, expr) 1
#define __step_let(var, expr) 0

BEGIN {
  loop (range(i, 1, 10),
        range_step(j, 1, 10, 2),
        let(ch, substr("abcdefghijklmn", i, j)))
  {
    print i, j, ch
  }
}
'
:
1 1 a
2 3 bcd
3 5 cdefg
4 7 defghij
5 9 efghijklm
--
9:
$cppawk '
#include <iter.h>

#define __init_first_then_until(var, first, then, until) (var = (first))
#define __test_first_then_until(var, first, then, until) (!(until))
#define __prep_first_then_until(var, first, then, until) 1
#define __fini_first_then_until(var, first, then, until) 1
#define __step_first_then_until(var, first, then, until) (var = (then))

BEGIN {
  loop (first_then_until(i, 1, i * 2, i >= 60),
        first_then_until(s, "x", s s, 0))
  {
    print i, s
  }
}'
:
1 x
2 xx
4 xxxx
8 xxxxxxxx
16 xxxxxxxxxxxxxxxx
32 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
--
10:
$cppawk '
#include <iter.h>
#include <cons.h>

BEGIN {
  $0 = "a b c" # set fields

  split("X Y", arr) # init array

  bags (b1, b2) {
    loop_nest (parallel(fields(f),
                        str(i, ch, "IJK")),
               keys(ky, arr),
               parallel(range(j, 1, 3),
                        from(k, 100)))
    {
       print f, ch, arr[ky], j, k
       bag(b1, j)
    }
  }

  print sexp(b1)
}'
:
a I X 1 100
a I X 2 101
a I X 3 102
a I Y 1 100
a I Y 2 101
a I Y 3 102
b J X 1 100
b J X 2 101
b J X 3 102
b J Y 1 100
b J Y 2 101
b J Y 3 102
c K X 1 100
c K X 2 101
c K X 3 102
c K Y 1 100
c K Y 2 101
c K Y 3 102
(1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3)
--
11:

$cppawk '
#include <iter.h>

BEGIN {
  loop (range(i, 1, 10),
        summing(s, i))
  {
    print s
  }
  print "sum =", s
}'
:
1
3
6
10
15
21
28
36
45
55
sum = 55
--
12:

$cppawk '
#include <iter.h>

BEGIN {
  loop (from_step   (vel, 5, -1),
        from_step   (pos, 0, vel),
        while       (pos >= 0),
        maximizing  (maxpos, pos))
  {
    print pos
  }
  print "maxpos =", maxpos
}'
:
0
4
7
9
10
10
9
7
4
0
maxpos = 10
--
13:

$cppawk '
#include <iter.h>

BEGIN {
  loop (from_step   (vel, 5, -1),
        from_step   (pos, 0, vel),
        until       (vel <= 0),
        maximizing  (maxpos, pos))
  {
    print pos
  }
  print "maxpos =", maxpos
}'
:
0
4
7
9
10
maxpos = 10
--
14:
$cppawk '
#include <iter.h>

BEGIN {
  loop (range_step  (x, 0, 3.14159, 0.001),
        argmax      (mx, x, sin(x) * cos(x)),
        argmin      (mi, x, sin(x) * cos(x)))
    ; // empty

  print "max x =", mx
  print "min x =", mi
}'
:
max x = 0.785
min x = 2.356
--
15:
$cppawk '
#include <iter.h>
#include <cons.h>

BEGIN {
  loop (list(tail, item, list(1, 2, 3, 0, 5, -3, 7)),
        minimizing(min, item))
  {
  }
  print "min =", min
}'
:
min = -3
--
16:
$cppawk '
#include <iter.h>
#include <cons.h>

function index_from(str, ch, start,
                    sstr, pos)
{
  sstr = substr(str, start)
  pos = index(sstr, ch)
  return pos ? pos + start - 1 : 0
}

function sscl(string, char)
{
  loop (first_then    (start, 1, end + 1),
        for_var       (end, index_from(string, char, start)),
        collect_plus  (out, end ? substr(string, start, end - start)
                                : substr(string, start)),
        while      (end))
  { }
  return out
}

BEGIN {
  print sexp(sscl(",", ","))
  print sexp(sscl("a,", ","))
  print sexp(sscl(",a", ","))
  print sexp(sscl("a,b,c", ","))
}'
:
(nil nil)
("a" nil)
(nil "a")
("a" "b" "c")
--
17:
$cppawk '
#include <iter.h>
#include <cons.h>

BEGIN {
  loop (range (i, 1, 10),
        if (i % 2 == 0, collect(l, i)))
  { }

  print sexp(l)
}'
:
(2 4 6 8 10)
--
18:
$cppawk '
#include <iter.h>

BEGIN {
  loop (range (i, 1, 10),
        if (i % 2 == 1, from(j, 1)))
  {
    print i, j
  }
}'
:
1 1
2 1
3 2
4 2
5 3
6 3
7 4
8 4
9 5
10 5
--
19:
$cppawk '
#include <iter.h>

BEGIN {
  loop (while (0),
        argmax (mx, x, sin(x)),
        argmin (mi, x, sin(x)))
    ; // empty

  print mx == "" && mx != 0
  print mi == "" && mi != 0
}'
:
1
1
--
20:
$cppawk '
#include <iter.h>

BEGIN {
  loop (range (x, -1, -1),
        argmax (mx, x, x),
        argmin (mi, x, x))
    ; // empty

  print mx
  print mi
}'
:
-1
-1
--
21:
$cppawk '
#include <iter.h>

BEGIN {
  loop (range (x, 1, 11),
        counting (oddc, x % 2 != 0),
        counting (evenc, x % 2 == 0),
        counting (negativec, x < 0))
     ;
  print oddc, evenc, negativec
}'
:
6 5 0
--
22:
$cppawk '
#include <iter.h>

BEGIN {
  OFS=":"
  loop (records("testdir/data")) {
    $1=$1
    print
  }
}'
:
a:b:c:d
e:f:g:h