On 12/16/2014 08:20 PM, Mick Jordan wrote:
vapply <- function(X, FUN, FUN.VALUE, ..., USE.NAMES = TRUE)
{
FUN <- match.fun(FUN)
if(!is.vector(X) || is.object(X)) X <- as.list(X)
.Internal(vapply(X, FUN, FUN.VALUE, USE.NAMES))
}
This is an implementor question. Basically, what happened to the '...' args in
the call to the .Internal? cf lapply:, where the ... is passed.
lapply <- function (X, FUN, ...)
{
FUN <- match.fun(FUN)
## internal code handles all vector types, including expressions
## However, it would be OK to have attributes which is.vector
## disallows.
if(!is.vector(X) || is.object(X)) X <- as.list(X)
##TODO
## Note ... is not passed down. Rather the internal code
## evaluates FUN(X[i], ...) in the frame of this function
.Internal(lapply(X, FUN, ...))
}
Now both of these functions work when extra arguments are passed, so evidently
the implementation can function whether the .Internal "call" contains the ... or
not. I found other cases, notably in S3 generic methods where the ... is not
passed down.
Hi Mick --
You can see that the source code doesn't contain '...' in the final line
~/src/R-devel/src/library/base/R$ svn annotate lapply.R | grep Internal\(l
38631 ripley .Internal(lapply(X, FUN))
and that it's been there for a long time (I'd guess 'forever')
~/src/R-devel/src/library/base/R$ svn log -r38631
------------------------------------------------------------------------
r38631 | ripley | 2006-07-17 14:30:55 -0700 (Mon, 17 Jul 2006) | 2 lines
another attempt at a faster lapply
------------------------------------------------------------------------
so I guess you're looking at a modified version of the function... The
implementation detail is in the comment -- FUN(X[i], ...) is evaluated in the
frame of lapply.
Martin Morgan
So, essentially, my question is whether the vapply code "should" be changed or
whether a .Internal implementation should always assume an implicit ...
regardless of the code, if the semantics requires it.
Thanks
Mick
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