the environment variables Sys.setenv(LANG = "C") sets
the locale categories Sys.setlocale("LC_COLLATE", "C") sets, and the language
the options options(digits = 3) sets
the graphics parameters par(mfrow = c(1, 2)) sets, on top of the whole graphics state
the entries of the search path (library(dplyr) adds dplyr, detach(package:dplyr) removes it)
The states made of named entries: setting one entry replaces its pseudo variable
#<state>:<key>, adds to the accumulatingallof the state, and an entry we cannot name adds to#<state>:*instead (options(op),Sys.setenv(...)).