[Rd] dput(as.list(function...)...) bug

[Wacek Kusnierczyk]

Stavros Macrakis wrote:
> Tested in R 2.8.1 Windows
>
>   
>> ff <- formals(function(x)1)
>> ff1 <- as.list(function(x)1)[1]
>>     
> # ff1 acts the same as ff in the examples below, but is a list rather
> than a pairlist
>
>   
>> dput( ff , control=c("warnIncomplete"))
>>     
> list(x = )
>
> This string is not parsable, but dput does not give a warning as specified.
>
>   

same in 2.10.0 r48200, ubuntu 8.04 linux 32 bit


>> dput( ff , control=c("all","warnIncomplete"))
>>     
> list(x = quote())
>   

likewise.

> This string is parseable, but quote() is not evaluable, and again dput
> does not give a warning as specified.
>
> In fact, I don't know how to write out ff$x.  It appears to be the
> zero-length name:
>
>     is.name(ff$x) => TRUE
>     as.character(ff$x) => ""
>
> but there is no obvious way to create such an object:
>
>     as.name("") => execution error
>     quote(``) => parse error
>
> The above examples should either produce a parseable and evaluable
> output (preferable), or give a warning.
>   

interestingly,

    quote(NULL)
    # NULL

    as.name(NULL)
    # Error in as.name(NULL) :
    #  invalid type/length (symbol/0) in vector allocation

æsj.

vQ

>             -s
>
> PS As a matter of comparative linguistics, many versions of Lisp allow
> zero-length symbols/names.  But R coerces strings to symbols/names in
> a way that Lisp does not, so that might be an invitation to obscure
> bugs in R where it is rarely problematic in Lisp.
>
> PPS dput(pairlist(23),control="all") also gives the same output as
> dput(list(23),control="all"), but as I understand it, pairlists will
> become non-user-visible at some point.
>
> ______________________________________________
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> https://stat.ethz.ch/mailman/listinfo/r-devel
>   


-- 
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Wacek Kusnierczyk, MD PhD

Email: waku at idi.ntnu.no
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