Get parent environments
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()) 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.
|
An environment for env_parent() and env_tail(), a list
of environments for env_parents().
# Get the parent environment with env_parent(): env_parent(global_env()) # Or the tail environment with env_tail(): env_tail(global_env()) # 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() env_parent(base_env()) # 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())
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