[plt-scheme] What are the semantics of optional variables?

But it doesn't seem to be properly documented, so I'll work on that.

At Thu, 26 Jun 2008 14:15:19 -0400, Matthias Felleisen wrote:
> 
> Yes.
> 
> On Jun 26, 2008, at 2:04 PM, David Einstein wrote:
> 
> > If I may join Circular function in asking annoying questions (co- 
> > sinning as it were), what exactly are the semantics of optional  
> > variables?
> > It appears from experiment that they are evaluated sequentially in  
> > environments containing the previously declared parameters, kind of  
> > like let*.
> > In fact, it appears that evaluation of optional parameters can  
> > safely[*] mutate earlier optional and non-optional parameters.
> >
> >
> > [*] but not necessarily sanely.  I've probably been writing too  
> > much R code
> >
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