[R] inc function .. more generally, var arguments

[John Aitchison]

Hi

I'd like to be able to write a simple 'increment' function (like inc in 
pascal or ++ in C++) that takes the argument and increments it 
'permanently'  ie so that z<-1; inc(z) # no assignment; z  #2

I can see how to do it with a global variable but that is not what I want -
 I want to modify the object that is the actual argument.. I have looked 
at  assign(), << etc .. I am not sure where to go next.

I thought I could possibly do it by reference to the calling environment
and tried

> inc
function(a){ eval.parent(a<-a+1,1) }
> z<-1
> inc(z)
[1] 2
> z
[1] 1
> 
no good

Is what I want to do possible?  (I realize that it is possibly inadvisable
as there would be no obvious way of knowing from the function
definition that it modified its arguments)

thanks


John Aitchison
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