On Thu, Feb 28, 2013 at 3:44 PM, Gabor Grothendieck <ggrothendi...@gmail.com> wrote: > This issues a message about a needing to be non-negative as expected: > > setClass("A", > representation = list(a = "numeric"), > prototype = list(a = 0), > validity = function(object) { > out <- if (object@a < 0) "a must be non-negative" > if (is.null(out)) TRUE else out ## > }) > new("A", a = -1) > > but it also works if the ## line is omitted so it appears that one can > use NULL in place of TRUE. I wonder if the use of NULL as an > alternative to TRUE could be officially supported as it would allow > one to write validity methods in a more concise manner. It appears > that this would only require a change to the documentation. >
Pressed return too quickly. This should have continued on to give this example: new("A") with and without the ## line both of which work since it appears that NULL can be used in place of TRUE. -- Statistics & Software Consulting GKX Group, GKX Associates Inc. tel: 1-877-GKX-GROUP email: ggrothendieck at gmail.com ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel