Cache a value in an environment

env_cache() is a wrapper around env_get() and env_poke() designed to retrieve a cached value from env.

• If the nm binding exists, it returns its value.

• Otherwise, it stores the default value in env and returns that.

env_cache(env, nm, default)

Arguments

env

An environment.

nm

Names of bindings. nm must be a single string.

default

The default value to store in env if nm does not exist yet.

Value

Either the value of nm or default if it did not exist yet.

Examples

e <- env(a = "foo")

# Returns existing binding
env_cache(e, "a", "default")
#> [1] "foo"

# Creates a `b` binding and returns its default value
env_cache(e, "b", "default")
#> [1] "default"

# Now `b` is defined
e$b
#> [1] "default"