Descending grade

idesc x    idesc[x]

Where x is a list or dictionary, returns the indices needed to sort list it in descending order.

q)L:2 1 3 4 2 1 2
q)idesc L
3 2 0 4 6 1 5
q)L idesc L
4 3 2 2 2 1 1
q)(desc L)~L idesc L
1b
q)idesc `a`c`b!1 2 3
`b`c`a