[Rd] The regular expressions in compareVersion()

Duncan Murdoch murdoch.duncan at gmail.com
Thu Apr 24 22:42:06 CEST 2014

On 24/04/2014, 1:11 PM, Yihui Xie wrote:
> Hi,
> I guess the backslash should not be used as the separator for
> strsplit() in compareVersion(), because the period in [.] is no longer
> a metacharacter (no need to "escape" it using a backslash):
> https://github.com/wch/r-source/blob/trunk/src/library/utils/R/packages.R#L866-L867
>> compareVersion
> function (a, b)
> {
> ....
>      a <- as.integer(strsplit(a, "[\\.-]")[[1L]])
>      b <- as.integer(strsplit(b, "[\\.-]")[[1L]])
> ....
> <environment: namespace:utils>

Could you post an example where this causes trouble, or are you just 
suggesting this as a way to make the source a little cleaner?

> A similar regular expression problem also exists in the Sweave syntax
> (for \Sexpr{}), and I have reported it once. It was fixed but the fix
> was immediately reverted for some reason:
> https://github.com/wch/r-source/commit/52b0a46e15136a7f9e4777e9960fdda6d84880c0

A link to your report would be more useful, if it included an example 
where the bad regexp causes trouble.

Duncan Murdoch

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