[R] matching last argument in function

[Gabor Csardi]

It should be possible i think. You just supply all the arguments via
'...' and then cut off the last one. I don't see why this wouldn't work,
but maybe i'm missing something.

Gabor

On Tue, Feb 12, 2008 at 12:58:25PM -0600, Erik Iverson wrote:
> Alistair -
> 
> I don't believe this is possible.  The only way formal arguments (like 
> expr) can be matched after a '...' is with *exact* name matching.  Why 
> do you want to avoid explicitly naming the expr argument?
> 
> If you always want the expr argument last, you might be able to just use 
> ... as the sole argument to your function, and strip off the last 
> element inside the function as 'expr', and use all but the last element 
> as your list of options.  This requires that expr always be given last 
> though.  Probably best just to explicitly name the expr argument.
> 
> Erik Iverson
> 
> Alistair Gee wrote:
> > I often want to temporarily modify the options() options, e.g.
> > 
> > a <- seq(10000001, 10000001 + 10) # some wide object
> > 
> > with.options <- function(..., expr) {
> >   options0 <- options(...)
> >   tryCatch(expr, finally=options(options0))
> > }
> > 
> > Then I can use:
> > 
> > with.options(width=160, expr = print(a))
> > 
> > But I'd like to avoid explicitly naming the expr argument, as in:
> > 
> > with.options(width=160, print(a))
> > 
> > How can I do this with R's argument matching? (I prefer the expr as
> > the last argument since it could be a long code block. Also, I'd like
> > with.options to take multiple options.)
> > 
> > TIA
> > 
> > ______________________________________________
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> 
> ______________________________________________
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> and provide commented, minimal, self-contained, reproducible code.

-- 
Csardi Gabor <csardi at rmki.kfki.hu>    UNIL DGM