R devel - Oct 2004 - Internal function isUME() in findGeneric() is wrong (PR#7320)

Full_Name: Jeff Hallman
Version: 2.0
OS: Linux
Submission from: (NULL) (132.200.32.34)


The function findGeneric() in the utils namespace contains this internal
function:

  isUME <- function(e) {
        if (is.call(e) && (is.name(e[[1]]) || is.character(e[[1]]))) {
            switch(as.character(e[[1]]), UseMethod = as.character(e[[2]]), 
                "{" = isUMEbrace(e), "if" = isUMEif(e),
"")
        }
        else ""
    }

This fails if the generic called UseMethod() without an argument, which is
perfectly legal.  Changing it to this seems to work:

  isUME <- function(e) {
    if(is.call(e) &&(is.name(e[[1]]) || is.character(e[[1]]))) {
      switch(as.character(e[[1]]), 
             UseMethod = ifelse(length(e) == 1, fname, as.character(e[[2]])), 
             "{" = isUMEbrace(e),
             "if" = isUMEif(e),
             "")
    }
    else ""
  }


Jeff

The issue is the use of UseMethod(), which you claim to be valid.  As it
is inconsistent with the prime documentation, the help page, I would
question if it is `perfectly legal'.  I expect the author of isUME
implemented the behaviour described on the help page.

It is documented in S-PLUS as *strongly discouraged*, and although it is
documented in R-lang, I believe the right thing to do is to make the code
agree with the prime documentation.

I see no uses of UseMethod() in the R sources, and on CRAN only
one in a comment (and none in BioC).

On Thu, 28 Oct 2004 jhallman@frb.gov wrote:
> Full_Name: Jeff Hallman
> Version: 2.0
> OS: Linux
> Submission from: (NULL) (132.200.32.34)
> 
> 
> The function findGeneric() in the utils namespace contains this internal
> function:
> 
>   isUME <- function(e) {
>         if (is.call(e) && (is.name(e[[1]]) ||
is.character(e[[1]]))) {
>             switch(as.character(e[[1]]), UseMethod = as.character(e[[2]]), 
>                 "{" = isUMEbrace(e), "if" = isUMEif(e),
"")
>         }
>         else ""
>     }
> 
> This fails if the generic called UseMethod() without an argument, which is
> perfectly legal.  Changing it to this seems to work:
> 
>   isUME <- function(e) {
>     if(is.call(e) &&(is.name(e[[1]]) || is.character(e[[1]]))) {
>       switch(as.character(e[[1]]), 
>              UseMethod = ifelse(length(e) == 1, fname,
as.character(e[[2]])),
>              "{" = isUMEbrace(e),
>              "if" = isUMEif(e),
>              "")
>     }
>     else ""
>   }
> 
> 
> Jeff
> 
> ______________________________________________
> R-devel@stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
> 
> 
-- 
Brian D. Ripley,                  ripley@stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
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