Problem Statement

Chess960 is a variant of chess created by world champion Bobby Fischer. Unlike other variants of the game, Chess960 does not require a different material, but instead relies on a random initial position, with a few constraints:

With those constraints there are 960 possible starting positions, thus the name of the variant.

The purpose of this task is to write a program that can randomly generate any one of the 960 Chess960 initial positions. You will show the result as the first rank displayed using either the chess symbols in Unicode (♔♕♖♗♘), the letters King Queen Rook Bishop kNight, or the corresponding letters in a language other than English.

Let's start with the solution:

row0=: u: 9812+2}.5|i.10
king=: u:9812
rook=: u:9814
bish=: u:9815
pos=: I.@e.
bishok=: 1=2+/ .| pos&bish
rookok=: pos&rook -: (<./,>./)@pos&(rook,king)
ok=: bishok*rookok
perm=: A.&i.~ !
valid=: (#~ ok"1) ~.row0{"1~perm 8
gen=: valid {~ ? bind 960


   gen''
♘♗♖♔♗♕♖♘
   gen''
♗♘♘♗♖♔♖♕
   gen''
♖♗♔♘♘♕♗♖
   gen''
♖♔♕♗♗♘♖♘