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When an object is modified, R generally copies it (sometimes lazily) to enforce value semantics. However, some internal types are uncopyable. If you try to copy them, either with <- or by argument passing, you actually create references to the original object rather than actual copies. Modifying these references can thus have far reaching side effects.

Usage

is_copyable(x)

Arguments

x

An object to test.

Examples

# Let's add attributes with structure() to uncopyable types. Since
# they are not copied, the attributes are changed in place:
env <- env()
structure(env, foo = "bar")
#> <environment: 0x55deb1ff1fb8>
#> attr(,"foo")
#> [1] "bar"
env
#> <environment: 0x55deb1ff1fb8>
#> attr(,"foo")
#> [1] "bar"

# These objects that can only be changed with side effect are not
# copyable:
is_copyable(env)
#> [1] FALSE

structure(base::list, foo = "bar")
#> function (...)  .Primitive("list")
#> attr(,"foo")
#> [1] "bar"
str(base::list)
#> function (...)  
#>  - attr(*, "foo")= chr "bar"