index of

      'ab' 1 'ef'[2]  ⍝ Dyalog APL
1
      'ab' 1 'ef'[2]  ⍝ GNU APL
 ab 1 f

rank

   'hello' ,"0 1 'there'  NB. J
hthere
ethere
lthere
lthere
othere
   1 2 3 ,"0 1 4 5 6
|length error
|   1 2 3,    "0 1 4 5 6
   1 2 3 ,"0 1 (4 5 6)
1 4 5 6
2 4 5 6
3 4 5 6