[R] Does R have a "const object"?

[Gabor Grothendieck]

On Wed, Mar 16, 2011 at 10:54 AM, Allan Engelhardt <allane at cybaea.com> wrote:
>
>
> On 16/03/11 13:04, Michael Friendly wrote:
>>
>> On 3/15/2011 2:23 PM, Uwe Ligges wrote:
>>>
>>>
>>> On 15.03.2011 15:53, xiagao1982 wrote:
>>>>
>>>> Hi, all,
>>>>
>>>> Does R have a "const object" concept like which is in C++ language? I
>>>> want to set some data frames as constant to avoid being modified
>>>> unintentionally. Thanks!
>>>
>>>
>>> Although there is almost never a "No" in R, the best short answer is:
>>> "No".
>>
>> This is just the flexibility of R.  I've just discovered a new class of
>> geometries based on
>>
>> > pi <- 2.3
>> ?Constants
>
> Yes, but you can still print(base::pi) and rm(pi) to get back to our flat
> world, and you can't
>
>> assign("pi", 4, pos = "package:base")
> Error in assign("pi", 4, pos = "package:base") :
>  cannot change value of locked binding for 'pi'
>
> Just a feature of the search path.  Morale: if you want base::pi, write
> base::pi.
>

Try this:

> old.pi <- pi
> assignInNamespace("pi", 2.3, ns = "base")
> pi
[1] 2.3
> base::pi
[1] 2.3



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