env_parent()
returns the parent environment of env
if called
with n = 1
, the grandparent with n = 2
, etc.
env_tail()
searches through the parents and returns the one
which has empty_env()
as parent.
env_parents()
returns the list of all parents, including the
empty environment. This list is named using env_name()
.
See the section on inheritance in env()
's documentation.
env_parent(env = caller_env(), n = 1) env_tail(env = caller_env(), last = global_env(), sentinel = NULL) env_parents(env = caller_env(), last = global_env())
env | An environment. |
---|---|
n | The number of generations to go up. |
last | The environment at which to stop. Defaults to the global environment. The empty environment is always a stopping condition so it is safe to leave the default even when taking the tail or the parents of an environment on the search path.
|
sentinel | This argument is defunct, please use |
An environment for env_parent()
and env_tail()
, a list
of environments for env_parents()
.
The sentinel
argument of env_tail()
has been deprecated in
rlang 0.2.0 and renamed to last
. It is defunct as of rlang 0.4.0.
#> <environment: package:rlang> #> attr(,"name") #> [1] "package:rlang" #> attr(,"path") #> [1] "/home/travis/R/Library/rlang"#> <environment: base># By default, env_parent() returns the parent environment of the # current evaluation frame. If called at top-level (the global # frame), the following two expressions are equivalent: env_parent()#> <environment: 0x2e48280>env_parent(base_env())#> <environment: R_EmptyEnv># This default is more handy when called within a function. In this # case, the enclosure environment of the function is returned # (since it is the parent of the evaluation frame): enclos_env <- env() fn <- set_env(function() env_parent(), enclos_env) identical(enclos_env, fn())#> [1] TRUE