On 15/03/2011 2:35 PM, Martin Morgan wrote:
On 03/15/2011 11:34 AM, Duncan Murdoch wrote:
> On 15/03/2011 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".
>
> Very nice answer! Achim, this is a fortune candidate if I ever saw one!
but aren't lockBinding / lockEnvironment a reasonable longer answer? Martin
I think the limitations would also need to be part of the long answer,
and probably a discussion of environments and scoping rules. For example,
x <- 1
lockBinding("x", environment())
f <- function() {
print(x) # I can see and print the locked variable
x <- 2 # And change it? (Not really....)
print(x)
}
f() # prints a 1 then a 2
Duncan Murdoch
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