numeric(0)[FALSE] bug[let]

[Martin Maechler]

This is not a joke, but a problem appearing in real code of mine.
I used ifelse in a context which can be simplified to

R> ifelse(T, 3, NULL)
Error: incompatible types in subset assignment
R> ifelse(T, 3, numeric(0))
Error: invalid subscript type
R> 
R> ifelse
function (test, yes, no) 
{
        ans <- test
        test <- as.logical(test)
        nas <- is.na(test)
        ans[test] <- rep(yes, length = length(ans))[test]
        ans[!test] <- rep(no, length = length(ans))[!test]
        ans[nas] <- NA
        ans
}
R> 
R> numeric(0)[F]
Error: invalid subscript type
R> NULL[F]
NULL
R> 

--------------------------------------------

whereas  S-plus does as I expect:

S> ifelse(T, 3, NULL)
[1] 3
S> ifelse(T, 3, numeric(0))
[1] 3
S> 
S> NULL[F]
NULL
S> numeric(0)[F]
numeric(0)
S> logical(0)[F]
logical(0)
S> 
-----------------
I see an easy workaround for either fixing  ifelse(.) and or
solving my problem.

However, I think

	anytype(0)[FALSE]  should  return   
	anytype(0)

Martin
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