[R] Can we get rid of && and ||?

[GB]

Confusion (mine!) continues. Replace '&&' with '&' in my reply!

Göran

On Thu, 13 Apr 2000, GB wrote:

> Bill,
> 
> thank you for the lesson! Just one question:
> 
> [snip]
> > I think you miss the point quite seriously.   
> 
> No and yes.
> 
> > Under the present semantics
> > in 'a & b' *both* a and b are *guaranteed* unconditionally to be evaluated,
> 
> I didn't miss this.
> 
> > and in a lazy evaluation language, especially, that unconditional evaluation
> > can be vital.   
> 
> I missed this. And I don't quite understand it (yet). In 'a && b', why
> would it be vital to evaluate  b  if  a  is  FALSE? Of course, in a
> construct like 'a && (b <- c)' it would, but isn't 'b <- c; a && b' more
> readible and to be recommended? (Or does the former code execute faster?)
> I think I need a good example here. Can you give me one?
> 
> Once again, thanks!
> 
> Göran
> ----------------------------------------------------------
>  Göran Broström                      tel: +46 90 786-5223
>  Department of Statistics            
>  Umeå University                                         
>  SE-90187 Umeå, Sweden              email: gb at stat.umu.se
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-- 
----------------------------------------------------------
 Göran Broström                      tel: +46 90 786-5223
 Professor                          fax: +46 90 786-6614
 Department of Statistics            
 Umeå University                                         
 SE-90187 Umeå, Sweden              email: gb at stat.umu.se
                                                        
 http://www.stat.umu.se/egna/gb    ftp://capa.stat.umu.se
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