R devel - Jul 2006 - often unnecessary duplicate in sapply / as.vector

sapply calls lapply as

    answer <- lapply(as.list(X), FUN, ...)

which, when X is a list, causes X to be duplicated unnecessarily. The
coercion is unnecessary for other mode(X) because in lapply we have

    if (!is.list(X)) X <- as.list(X)

More generally, perhaps as.vector might not duplicate when mode(x) == mode ?

Martin


R version 2.4.0 Under development (unstable) (2006-07-05 r38495) 
x86_64-unknown-linux-gnu 

locale:
LC_CTYPE=en_US;LC_NUMERIC=C;LC_TIME=en_US;LC_COLLATE=en_US;LC_MONETARY=en_US;LC_MESSAGES=en_US;LC_PAPER=en_US;LC_NAME=C;LC_ADDRESS=C;LC_TELEPHONE=C;LC_MEASUREMENT=en_US;LC_IDENTIFICATION=C

attached base packages:
[1] "tools"     "methods"   "stats"    
"graphics"  "grDevices" "utils"
[7] "datasets"  "base"

On Fri, 7 Jul 2006, Martin Morgan wrote:
> sapply calls lapply as
>
>    answer <- lapply(as.list(X), FUN, ...)
>
> which, when X is a list, causes X to be duplicated unnecessarily. The
> coercion is unnecessary for other mode(X) because in lapply we have
>
>    if (!is.list(X)) X <- as.list(X)
That looks reasonable.
> More generally, perhaps as.vector might not duplicate when mode(x) == mode
?
>
This isn't a trivial change, because  mode(x)==mode does not guarantee 
that as.vector(x, mode) has no effect.  For example, with
mode="numeric" it
removes attributes.


         -thomas

Thomas Lumley			Assoc. Professor, Biostatistics
tlumley at u.washington.edu	University of Washington, Seattle