On Sat, 26 Jul 2003 14:24:48 +0100, you wrote: >Am Samstag, 26. Juli 2003 11:38 schrieb Peter Dalgaard BSA:
>> I think it basically has to be so: For one thing, it is kind of >> difficult to check for a signature match without evaluating the >> arguments and the left hand side of an assignment will not in general >> exist at that point. > >In the methods is the class "missing". Could that help? >for one thing : signature=c("missing","A") (only allowed for <- ?) >for both things: signature=c("A","B") >for nothing ;-) : signature=c("missing","missing") But A isn't missing in "A <- B"; I can see it right there! It might make sense to require that "<-" methods have "ANY" as the type of the first argument. It's part of the semantics of the language that the result of "A <- B" does not depend on the value of A in any way, and that shouldn't be changed. Duncan Murdoch ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help