On Fri, 27 Feb 2004, Paul Gilbert wrote:Ok. Will two S4 generics co-exist? Perhaps the S4 generics should be defined in base just in case someone else wants to to have an S4 start method too? (This would apply to a lot of other S3 generics in addition to start.)
Prof Brian Ripley wrote:
On Fri, 27 Feb 2004, Swinton, Jonathan wrote:I'm confused (not for the first time). I can see that namespaces are an additional problem, but I thought the original question was about defining an S4 generic "start."
From: Prof Brian Ripley <[EMAIL PROTECTED]>
Subject: Re: [Rd] package 'stats' needs import directive for 1.9.0?
To: "Heywood, Giles" <[EMAIL PROTECTED]>
Cc: [EMAIL PROTECTED]
...It is not easily possible if namespaces are involved. We failed to anticpate that we would need version-dependent namespaces until rather late and then decided not to set up an elaborate solution when most people affected had already made separate versions for 1.9.0.
I suggest you don't try: there are already quite a few 1.9.0-specific versions of packages on CRAN, and 1.8.x will be history in a couple of months.I'm not sure I understand the advice here. I have also hit the same problem,
and it seems reasonable to me to aspire to maintain a single package which
works on both 1.8.x and 1.9.x.
That's not what the subject line says, and the problem I was addressing is that the NAMESPACE file needs to be different in 1.8.1 and 1.9.0-to-be.
This would conflict (and override?) the S3 generic in base, which I don't think is allowed in 1.9.0. Until recently I have been overriding the start function in base (and some others) with my own S3 generic, and have just gone through a rather lengthy exercise to rename these functions and some objects and other methods so that things do work in 1.9.0. (They do also work in 1.8.1.)
Will S3 and S4 generics for start co-exist? What happens to all the S3 methods for start if the S4 generic is loaded? Won't this break a lot of code other than mine?
There should be no problem with an S4 generic, as it calls the actual existing S3 generic as its default S4 method. It's done for plot(), for example. What will not work is having a different S3 generic of the same name in a different namespace (including in the residual non-namespace).
Paul Gilbert
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