Damn scoping in R
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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:
1 2 3 4 5 6 | fun=function() { if (runif(1) > .5) x = 1 x } |
First it looks damn unspectacular. But wait, whats that:
1 2 3 4 5 | > 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? :-)
1 2 | > 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…
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