deep

Consumes an integer index and a lambda below it, and applies the lambda at that index in the stack. Indexes wrap around the stack, and negative indexes start at the bottom of the stack.

1 2 3 4 5 ( copy * ) 2 deep → 1 2 9 4 5

true false false ( copy copy ) -1 deep → true true true false false

1 2 3 4 5 ( drop drop ) 8 deep → 3 4 5