[R] understanding recursive functions

[Wacek Kusnierczyk]

Peter Dalgaard wrote:
> Wacek Kusnierczyk wrote:
>>
>>>
>>> "  The operators '<<-' and '->>' cause a search to made through the
>>>      environment for an existing definition of the variable being
>>>      assigned.  If such a variable is found (and its binding is not
>>>      locked) then its value is redefined, otherwise assignment takes
>>>      place in the global environment.  Note that their semantics differ
>>>      from that in the S language, but are useful in conjunction with
>>>      the scoping rules of R.  See 'The R Language Definition' manual
>>>      for further details and examples."
>>>
>>>   
>>
>> the description is further imprecise as to what happens if such a
>> variable is found but is locked:
>>
>> foo = function() {
>>    x = 0
>>    lockBinding("x", environment())
>>    (function() x <<- 1)()
>>    unlockBinding("x", environment())
>> }
>>
>> foo()
>> # error
>>
>> if analysed logically (IF (found AND not locked THEN assign) ELSE assign
>> globally), the description is wrong. 
>
> Yes.
>
> If such a variable is found  then its value is redefined (unless its
> binding is locked), otherwise assignment take place in the global
> environment.
>
   
it might help the help to be have the help say that if the variable is
found but locked then an error is raised.

vQ