Damn scoping in R

Ok, R is very well-considered in certain respects, but there are also some things annoying me… This time it’s scoping…

Let’s have a look to the following code:

fun=function()
{
	if (runif(1) > .5)
		x = 1
	x
}

First it looks damn unspectacular. But wait, whats that:

> x=0
> fun()
[1] 1
> fun()
[1] 0

Taking a closer look to the function shows that the returned value is randomly chosen from local ( runif(1) > .5 ) or global scope ( runif(1) <= .5 ). So you can’t expect a result from this function. Nasty, especially while debugging external code, isn’t it? :-)

> sum(sapply(1:10^6, function (null) fun()))/10^6
[1] 0.499681

So again my advise: Think about such specific features! This won’t happen in any sensible language…