env_parent: Get parent environments

In hadley/rlang: Functions for Base Types and Core R and 'Tidyverse' Features

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. This list is named using env_name().

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

Usage

env_parent(env = caller_env(), n = 1)

env_tail(env = caller_env(), last = global_env())

env_parents(env = caller_env(), last = global_env())

Arguments

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. env_tail() returns the environment which has last as parent and env_parents() returns the list of environments up to last.

Value

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

Examples

# 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())

hadley/rlang documentation built on Dec. 17, 2024, 3:26 a.m.