How code accesses a part of the global state, see AmbientAccess.
the state is only assumed changed by a body flowR cannot see, like #rng for function(f) f()
#rng
function(f) f()
the code changes the state in the current frame only
the code may read the state
the code may change the state
How code accesses a part of the global state, see AmbientAccess.