R help - Mar 2004 - if exists with regex return

Hello
I am trying for an hour now,  
> p <- "c:/data/"
or 
> p <- "c:/data/abc.hig"
	
d <- sub("(.+/.+?/)(.+)","\\1",p,perl=TRUE)
f <- sub("(.+/.+?/)(.+)?","\\2",p,perl=TRUE)

if (exists("f")){ #why this gives TRUE no mater what?
do this with d and f
} else {
do that with d
}


thanks

You assigned `f' whatever the result of
sub("(.+/.+?/)(.+)?","\\2",p,perl=TRUE) is.  The only way
for `f' not to
exist after that assignment (that I can think of anyway) is if there was an
error raised in the sub() call.  Otherwise `f' will always exist!  You
should simply check what value `f' has.  My guess is that you really want
something like:

  if (f == "") ...

or maybe:

  if (nchar(f) == 0) ...

Andy
> From: Fred J.
> 
> Hello
> I am trying for an hour now,  
> 
> > p <- "c:/data/"
> or 
> > p <- "c:/data/abc.hig"
> 	
> d <- sub("(.+/.+?/)(.+)","\\1",p,perl=TRUE)
> f <- sub("(.+/.+?/)(.+)?","\\2",p,perl=TRUE)
> 
> if (exists("f")){ #why this gives TRUE no mater what?
> do this with d and f
> } else {
> do that with d
> }
> 
> 
> thanks
> 
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