Set a Function's Environment — crate

Useful to represent functions efficiently within repr().

crate_env(fun, namespace = "R_GlobalEnv", ..., selfref = NULL)

Arguments

fun: (function)
Function of which the environment should be set.
namespace: (character(1))
Name of the namespace, as given by environmentName(), to be used as the (parent of the) environment of fun. Special values "R_GlobalEnv" (global environment), "R_BaseEnv" (base environment; note this one is non-standard within R), "R_EmptyEnv" (empty environment). The content of the namespace is not modified. Default "R_GlobalEnv".
...: (list)
Content of environments within which to place fun.
selfref: (character(1) | named integer | NULL)
If character(1): The name of the entry of the first element in ... that refers to the function itself. If a named integer, then the values indicate the lists in ... where the reference to the function should be placed see examples. Default NULL: No reference to the function itself is present.

Value

function: The given fun with changed environment.

Examples


identity2 = crate_env(function(x) x, "base")
identical(identity, identity2)  # TRUE
#> [1] TRUE

y = 1
f1 = mlr3misc::crate(function(x) x + y, y, .parent = .GlobalEnv)
f2 = crate_env(function(x) x + y, "R_GlobalEnv", list(y = 1))

# Note identical() does not apply because both contain (equal, but not
# identical) 'y = 1'-environments
all.equal(f1, f2)  # TRUE
#> [1] TRUE
f1(10)  # 10 + 1 == 11
#> [1] 11

factorial1 = mlr3misc::crate(
  function(x) if (x > 0) x * factorial1(x - 1) else 1,
  y, .parent = .GlobalEnv
)
environment(factorial1)$factorial1 = factorial1

factorial2 = crate_env(
  function(x) if (x > 0) x * factorial1(x - 1) else 1,
  "R_GlobalEnv", list(y = 1), selfref = "factorial1")
# putting 'factorial1' into the list (or repeating function(x) ....)
# would *not* work, since we want:
identical(environment(factorial2)$factorial1, factorial2)  # TRUE
#> [1] TRUE

all.equal(factorial1, factorial2)  # TRUE
#> [1] TRUE

g = crate_env(function(x) x + y + z, "miesmuschel",
  list(y = 1), list(z = 2), selfref = c(X = 1, Y = 2, Z = 2))
g(0)  # 0 + 1 + 2 == 3
#> [1] 3
identical(environment(g)$X, g)
#> [1] TRUE
identical(parent.env(environment(g))$Y, g)
#> [1] TRUE
identical(parent.env(environment(g))$Z, g)
#> [1] TRUE
identical(
  parent.env(parent.env(environment(g))),
  loadNamespace("miesmuschel")
)
#> [1] TRUE