Evaluates and returns the argument selected by which.
$(nth, which, arg0 [, arg1,…, arg7])
If which is 0, nth returns arg0, and so on. Note the difference between $(nth) and $(index); $(nth)returns one of a series of arguments to the function, while $(index) extracts a value from a comma-delimited string passed as a single argument. Arguments not selected by which are not evaluated.
