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List:       r-devel
Subject:    Re: [Rd] R 2.7.0, match() and strings containing \0 - bug?
From:       Herve Pages <hpages () fhcrc ! org>
Date:       2008-04-28 22:43:00
Message-ID: 481652F4.30706 () fhcrc ! org
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Hi Jon,

Jon Clayden wrote:
> Hi,
> 
> A piece of my code that uses readBin() to read a certain file type is
> behaving strangely with R 2.7.0. This seems to be because of a failure
> to match() strings after using rawToChar() when the original was
> terminated with a "\0" character. Direct equality testing with ==
> still works as expected. I can reproduce this as follows:
> 
>> x <- "foo"
>> y <- c(charToRaw("foo"),as.raw(0))
>> z <- rawToChar(y)
>> z==x
> [1] TRUE
>> z=="foo"
> [1] TRUE
>> z %in% c("foo","bar")
> [1] FALSE
>> z %in% c("foo","bar","foo\0")
> [1] FALSE

But this gives TRUE:

   > z %in% c("foo","bar", z)
   [1] TRUE

An additional problem you have here is that when the "foo\0" string literal
is converted into a character string, then the string data that are after the
first embedded nul are dropped:

   > identical("foo\0a\0b", "foo")
   [1] TRUE

And to add to the endless source of surprises that come with embedded nuls:

   > dump("z", file="")
   z <-
   "foo\0"

but of course sourcing the above dump into an R session will not restore 'z'.

Dropping support for embedded nuls in R 2.8.0 sounds like good news to me.

Cheers,
H.


> 
> But without the nul character it works fine:
> 
>> zz <- rawToChar(charToRaw("foo"))
>> zz %in% c("foo","bar")
> [1] TRUE
> 
> I don't see anything about this in the latest NEWS, but is this
> expected behaviour? Or is it, as I suspect, a bug? This seems to be
> new to R 2.7.0, as I said.
> 
> Regards,
> Jon
> 
> ______________________________________________
> R-devel@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>

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