[Rd] Part of fastpass in 'sort.list' can make sorting unstable

[luke-tierney at uiowa.edu]

Thanks -- fixed in R-devel and R-3-5-branch.

luke

On Fri, 6 Apr 2018, Suharto Anggono Suharto Anggono via R-devel wrote:

> In the code of functions 'order' and 'sort.list' in R 3.5.0 alpha (in https://svn.r-project.org/R/branches/R-3-5-branch/src/library/base/R/sort.R), in "fastpass, take advantage of ALTREP metadata", there is "try the reverse since that's easy too...". If it succeeds, ties are reordered, violating stability of sorting.
>
> Example:
> x <- sort(c(1, 1, 3))
> x  # 1 1 3
> sort.list(x, decreasing=TRUE)  # should be 3 1 2
>
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-- 
Luke Tierney
Ralph E. Wareham Professor of Mathematical Sciences
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