Just don't do it, surely? (was RE: [R] Retrieve ... argument values)

[Simon Fear]

Tony, I don't understand what you mean. Could you give
an example?

> -----Original Message-----
> From: Tony Plate [mailto:tplate at blackmesacapital.com]
> > ... I'm not saying "never write functions that use ...",
> >I'm just saying "never write functions that depend on a particular
> >argument being passed via ...".
> 
> Several reasons for not following that principle involve proliferation
> of 
> defaults -- if the lower level functions have defaults, then those
> defaults 
> must be repeated at the higher levels.  
> This is a good reason for not 
> following that principle, because it makes software maintenance more 
> difficult.  

I don't think I agree with that (though maybe I just didn't
get it). I prefer to know what arguments a function is going
to use.

> Another reason for not following that principle is that tf
> you 
> have several lower level functions with different default 
> values for an 
> argument of the same name, it becomes impossible to get the 
> lower-level 
> default behavior.

I'm lost there. When I choose which function to call it has
its own default??

I often call a function of mine called timepoints.summary for which I
want
to pass graphical parameters to boxplots, matplots and confidence
interval plots. So I name the arguments cex.boxplot, col.boxplot etc
and then within the function I call boxplot(x, cex=boxplot.cex) and so
on. I wouldn't expect a single argument "cex" to magically work out
whether it was being used in a boxplot or matplot and change
to a different default??
 

Simon Fear
Senior Statistician
Syne qua non Ltd
Tel: +44 (0) 1379 644449
Fax: +44 (0) 1379 644445
email: Simon.Fear at synequanon.com
web: http://www.synequanon.com
 
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