Oh yes, I forgot about its pass-by-value. Removing pass-by-value is a double edged sword though. I generally dislike it, but you have to admit that having every

Oh yes, I forgot about its pass-by-value. Removing pass-by-value is a double edged sword though. I generally dislike it, but you have to admit that having everything pass-by-value is much simpler to a non-programmer. If you chop that out then the "fast R subset" suddenly can act very differently. In order to really write efficient code you'd want to start making use of mutation on this fast part. This means throwing a macro on some array-based R code won't really be automatic: it would need a bit of a re-write for full speed but the re-written version would be incompatible with pass-by-value semantics. This is quite an interesting and tough problem to solve. I think it might be better to keep things pass-by-value and try to optimize pure functions.