From A List, Build or Add To an Environment

Description

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

Usage

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

Arguments

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.

Details

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.

Value

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.

Author(s)

Martin Maechler

See Also

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

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

Examples

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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)

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