_drop not defined

[tomeru]

In the "markov chains with lag" example, in chapter 6 here:

https://www.probmods.org/inference-process.html

The following use of "drop":

(hist (drop (chain 'a 100) 30) "burn-in 30, lag 0")

returns the error:

_drop is not defined

[longouyang]

Closed in probmods/webchurch@46d45106c9923a67a2f09eb796a7619188c7446a