[Rd] Feature suggestion

[Duncan Murdoch]

The R sources already contain an operator like that, though it is not 
exported.  tools:::`%notin%` is defined as

  function (x, y)
  is.na(match(x, y))

Several CRAN packages export a similar function, e.g. omnibus, mefa4, 
data.table, hutils, etc. So I think if it was exported by R that's a 
better name, but since it is easy to write yourself or import from some 
other package, why bother?

Duncan Murdoch



On 2025-11-27 9:19 a.m., Marcelo Ventura Freire via R-devel wrote:
> Hello, dear R core developers
> 
> 
> I have a feature suggestion and, following the orientations in
> https://contributor.r-project.org/rdevguide/chapters/submitting_feature_requests.html,
> I have searched in Bugzilla to the best of my capabilities for suggestions
> like the one I have in mind but found no results (however, I can be wrong).
> 
> My idea is including this line
> 
> `%!in%`  <- function(x, table) match(x, table, nomatch = 0L) == 0L
> 
> between lines 39 and 40 of the file "src/library/base/R/match.R".
> 
> My objective is to create a "not in" operator that would allow us to write
> code like
>>     value %!in% valuelist
> instead of
>>     ! value %in% valuelist
> which is in line with writing
>>     value1 != value2
> instead of
>>     ! value1 == value2
> 
> I was not able to devise any reasonable way that such inclusion would break
> any already existing heritage code unless that operator would be defined
> otherwisely and it would improve (however marginally) the readability of
> future code by its intuitive interpretation and by stitching together two
> operators that currently stand apart each other.
> 
> So, if this suggestion was not already proposed and if it is seen as
> useful, I would like to include it in the wishlist in Bugzilla.
> 
> I would appreciate any feedback, be it critic or support, and I hope I have
> not crossed any communicational rule from the group.
> 
> Many thanks!  😄
> 
> 
> 
> Marcelo Ventura Freire
> Escola de Artes, Ciências e Humanidades
> Universidade de São Paulo
> Av. Arlindo Bettio, 1000,
> Sala Paulo Freire (Sala Coletiva 252), Prédio I1
> Ermelino Matarazzo, São Paulo, SP, Brasil
> CEP 03828-000
> Tel.: (11) 3091-8894
> 
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> 
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