Note that in Example 6.1 of the text, which describes the Robot delivery environment, the text says that the effect of the dc (deliver coffee) operator is to make RHC (Rob Has Coffee) true. this is an error. The effect of the dc operator is to make RHC false (and swc false, which the text correctly states). The effects of dc are correctly stated in Example 6.5.
This error was corrected in the online version of the book before Fall 2018 class, but it may persist in hardcopies of the book