These functions dispatch internally with methods for functions, formulas and frames. If called with a missing argument, the environment of the current evaluation frame (see ctxt_stack()) is returned. If you call get_env() with an environment, it acts as the identity function and the environment is simply returned (this helps simplifying code when writing generic functions for environments).

get_env(env = caller_env(), default = NULL)

set_env(env, new_env = caller_env())

Arguments

env

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

default

The default environment in case env does not wrap an environment. If NULL and no environment could be extracted, an error is issued.

new_env

An environment to replace env with. Can be an object handled by get_env().

Examples

# Get the environment of frame objects. If no argument is supplied, # the current frame is used: fn <- function() { list( get_env(call_frame()), get_env() ) } fn()
#> [[1]] #> <environment: 0x7f97a082d188> #> #> [[2]] #> <environment: 0x7f97a082d188> #>
# Environment of closure functions: get_env(fn)
#> <environment: 0x7f97a085fb78>
# Or of quosures or formulas: get_env(~foo)
#> <environment: 0x7f97a085fb78>
get_env(quo(foo))
#> <environment: 0x7f97a085fb78>
# Provide a default in case the object doesn't bundle an environment. # Let's create an unevaluated formula: f <- quote(~foo) # The following line would fail if run because unevaluated formulas # don't bundle an environment (they didn't have the chance to # record one yet): # get_env(f) # It is often useful to provide a default when you're writing # functions accepting formulas as input: default <- env() identical(get_env(f, default), default)
#> [1] TRUE
# set_env() can be used to set the enclosure of functions and # formulas. Let's create a function with a particular environment: env <- child_env("base") fn <- set_env(function() NULL, env) # That function now has `env` as enclosure: identical(get_env(fn), env)
#> [1] TRUE
identical(get_env(fn), get_env())
#> [1] FALSE
# set_env() does not work by side effect. Setting a new environment # for fn has no effect on the original function: other_env <- child_env(NULL) set_env(fn, other_env)
#> function() NULL #> <environment: 0x7f979bb70150>
identical(get_env(fn), other_env)
#> [1] FALSE
# Since set_env() returns a new function with a different # environment, you'll need to reassign the result: fn <- set_env(fn, other_env) identical(get_env(fn), other_env)
#> [1] TRUE