rlang (version 0.2.1)

env_parent: Get parent environments

Description

• 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.

See the section on inheritance in env()'s documentation.

Usage

env_parent(env = caller_env(), n = 1)
env_tail(env = caller_env(), sentinel = empty_env())
env_parents(env = caller_env())

Arguments

env

An environment or an object bundling an environment, e.g. a formula, quosure or closure.

n

The number of generations to go up.

sentinel

The environment signalling the end of the linear search. env_tail() returns the environment which has sentinel as parent.

Value

An environment for env_parent() and env_tail(), a list of environments for env_parents().

Examples

# NOT RUN {
# 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())
# }