list2env: From A List, Build or Add To an Environment
In robertzk/monadicbase: The R Base Package

Description Usage Arguments Details Value Author(s) See Also Examples

From a named list x, create an environment containing all list components as objects, or “multi-assign” from x into a pre-existing environment.

1 2	list2env(x, envir = NULL, parent = parent.frame(), hash = (length(x) > 100), size = max(29L, length(x)))

`x`	a `list`, where `names(x)` must not contain empty (`""`) elements.
`envir`	an `environment` or `NULL`.
`parent`	(for the case `envir = NULL`): a parent frame aka enclosing environment, see `new.env`.
`hash`	(for the case `envir = NULL`): logical indicating if the created environment should use hashing, see `new.env`.
`size`	(in the case `envir = NULL, hash = TRUE`): hash size, see `new.env`.

This will be very slow for large inputs unless hashing is used on the environment.

Environments must have uniquely named entries, but named lists need not: where the list has duplicate names it is the last element with the name that is used. Empty names throw an error.

An environment, either newly created (as by new.env) if the envir argument was NULL, otherwise the updated environment envir. Since environments are never duplicated, the argument envir is also changed.

Martin Maechler

environment, new.env, as.environment; further, assign.

The (semantical) “inverse”: as.list.environment.

L <- list(a = 1, b = 2:4, p = pi, ff = gl(3, 4, labels = LETTERS[1:3]))
e <- list2env(L)
ls(e)
stopifnot(ls(e) == sort(names(L)),
          identical(L$b, e$b)) # "$" working for environments as for lists

## consistency, when we do the inverse:
ll <- as.list(e)  # -> dispatching to the as.list.environment() method
rbind(names(L), names(ll)) # not in the same order, typically,
                           # but the same content:
stopifnot(identical(L [sort.list(names(L ))],
                    ll[sort.list(names(ll))]))

## now add to e -- can be seen as a fast "multi-assign":
list2env(list(abc = LETTERS, note = "just an example",
              df = data.frame(x = rnorm(20), y = rbinom(20, 1, pr = 0.2))),
         envir = e)
utils::ls.str(e)