hb@maths.lth.se writes:
> match the argument 'x' if there is another argument with prefix
'x'
>
> Full_Name: Henrik Bengtsson
> Version: 1.3.1
> OS: Sun Solaris 8
> Submission from: (NULL) (130.235.3.49)
>
>
> I ran into a strange problem with UseMethod(). Run the following code:
>
> foo.Bar <- function(this, x=0, xidx=0) {
> cat("In foo.Bar(): ", this, ", x=", x, ",
xidx=", xidx, ".\n", sep="");
> }
>
> foo.default <- function(x, ...) {
> str("Error: No default function found!");
> }
>
> foo <- function(x, ...) UseMethod("foo");
>
>
> obj <- "Hello world!";
> class(obj) <- "Bar";
>
> foo(obj);
> foo(obj, xidx=1);
> foo(obj, x=1); # <- PROBLEM HERE!
> foo(obj, x=1, xidx=1); # <- PROBLEM HERE!
> foo(obj, xidx=1, x=1); # <- PROBLEM HERE!
> foo.Bar(obj, x=1);
> foo.Bar(obj, x=1, xidx=1);
>
> and you will get
>
> In foo.Bar(): Hello world!, x=0, xidx=0.
> In foo.Bar(): Hello world!, x=0, xidx=1.
> chr "Error: No default function found!"
> chr "Error: No default function found!"
> chr "Error: No default function found!"
> In foo.Bar(): Hello world!, x=1, xidx=0.
> In foo.Bar(): Hello world!, x=1, xidx=1.
>
> There is something going on with matching of arguments; UseMethod() fails
to
> match the argument 'x' if there is another argument with prefix
'x'.
>
> I believe this is an unwanted feature of UseMethod.
Nope. In all the three cases you've marked as problems, you're telling
foo that the "x" argument is 1 (cf. plot(rnorm(10),x=1:10) ) and thus
UseMethod dispatches the default method.
--
O__ ---- Peter Dalgaard Blegdamsvej 3
c/ /'_ --- Dept. of Biostatistics 2200 Cph. N
(*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk) FAX: (+45) 35327907
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