> Out of curiosity, do you have a good solution without the use of a lambda? > "pure SO APL" if you like.
I don't know how to do it in GNU APL. In Dyalog you can play silly
games with ∘ (function composition) and ⍨, e.g.:
⎕ML←1 ⍝ ↑ is mix and ↓ is split
↑(⌷⍨∘(⊂∘⍋))⍨¨↓X ⍝ N.B. ⍵[⍋⍵] ←→ (⊂⍋⍵)⌷⍵
xz
xz
ab
ab
(Dyalog version 14, currently in beta release, supports the rank
operator so you will be able to use it instead of split and mix.)
Jay.
