[Rd] Field initialization order bug?

[Prof Brian Ripley]

On Mon, 16 Jul 2007, Daniel Wilhelm wrote:

> I believe that I may have found a bug in R. The top code sample gives

You have 'merely' found a bug in your understanding.  What type did you 
expect 'a' to be?  If you expected a list, that is not what happens in the 
first example, and you need

a <- list()

or, better,

a <- vector("list", 2)

> an error as shown. However, by simply switching which field is
> initialized first as in the bottom code sample, it works as expected.
>
>
> This gives an error:
>
>
> a <- NULL
> a[["field1"]] <- 1

Now a is numeric

> a[["field2"]] <- matrix(c(2,1), 1)
>
> Error in a[["field2"]] <- matrix(c(2, 1), 1) :
> 	more elements supplied than there are to replace
>
>
>
> Yet, this works as expected:
>
> a <- NULL
> a[["field2"]] <- matrix(c(2,1), 1)

Now a is a list

> a[["field1"]] <- 1
>
>
>
> Daniel Wilhelm
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595