From m@ech|er @end|ng |rom @t@t@m@th@ethz@ch  Wed Aug 11 08:59:30 2021
From: m@ech|er @end|ng |rom @t@t@m@th@ethz@ch (Martin Maechler)
Date: Wed, 11 Aug 2021 08:59:30 +0200
Subject: [Rd] problem with pipes, textConnection and read.dcf
In-Reply-To: <A454DA3A-BD8D-418C-90FC-E5DE1CBB0725@gmail.com>
References: <CAP01uRn+6zWEgmyGfNTb3aJJoLCy8mbhJFj6SiWWBktmXwsncA@mail.gmail.com>
 <A454DA3A-BD8D-418C-90FC-E5DE1CBB0725@gmail.com>
Message-ID: <24851.30034.457559.988756@stat.math.ethz.ch>

>>>>> peter dalgaard 
>>>>>     on Tue, 10 Aug 2021 22:00:16 +0200 writes:

    > It's not a pipe issue:

    >> textConnection(gsub(gsub(L, pattern = " ", replacement = ""), pattern = " ", replacement = ""))
    > Error in textConnection(gsub(gsub(L, pattern = " ", replacement = ""),  : 
    > argument 'object' must deparse to a single character string
    >> textConnection(gsub(L, pattern = " ", replacement = ""))
    > A connection with                                                          
    > description "gsub(L, pattern = \" \", replacement = \"\")"
    > class       "textConnection"                              
    > mode        "r"                                           
    > text        "text"                                        
    > opened      "opened"                                      
    > can read    "yes"                                         
    > can write   "no"                                          

    > I suppose the culprit is that the deparse(substitute(...)) construct in the definition of textConnection() can generate multiple lines if the object expression gets complicated.

    >> textConnection
    > function (object, open = "r", local = FALSE, name = deparse(substitute(object)), 
    > encoding = c("", "bytes", "UTF-8")) 

    > This also suggests that setting name=something might be a cure.

    > -pd

Indeed.

In R 4.0.0, I had introduced the deparse1() short cut to be used
in place of  deparse() in such cases:

NEWS has said

    ? New function deparse1() produces one string, wrapping deparse(),
      to be used typically in deparse1(substitute(*)), e.g., to fix
      PR#17671.

and the definition is a simple but useful oneliner

  deparse1 <- function (expr, collapse = " ", width.cutoff = 500L, ...) 
  paste(deparse(expr, width.cutoff, ...), collapse = collapse)


So I'm almost sure we should use  deparse1() in textConnection
(and will make check and potentially commit that unless ...)

Martin


    >> On 10 Aug 2021, at 21:33 , Gabor Grothendieck <ggrothendieck at gmail.com> wrote:
    >> 
    >> This gives an error bit if the first gsub line is commented out then there is no
    >> error even though it is equivalent code.
    >> 
    >> L <- c("Variable:id", "Length:112630     ")
    >> 
    >> L |>
    >> gsub(pattern = " ", replacement = "") |>
    >> gsub(pattern = " ", replacement = "") |>
    >> textConnection() |>
    >> read.dcf()
    >> ## Error in textConnection(gsub(gsub(L, pattern = " ", replacement = ""),  :
    >> ##  argument 'object' must deparse to a single character string
    >> 
    >> That is this works:
    >> 
    >> L |>
    >> # gsub(pattern = " ", replacement = "") |>
    >> gsub(pattern = " ", replacement = "") |>
    >> textConnection() |>
    >> read.dcf()
    >> ##      Variable Length
    >> ## [1,] "id"     "112630"
    >> 
    >> R.version.string
    >> ## [1] "R version 4.1.0 RC (2021-05-16 r80303)"
    >> win.version()
    >> ## [1] "Windows 10 x64 (build 19042)"
    >> 
    >> -- 
    >> Statistics & Software Consulting
    >> GKX Group, GKX Associates Inc.
    >> tel: 1-877-GKX-GROUP
    >> email: ggrothendieck at gmail.com
    >> 
    >> ______________________________________________
    >> R-devel at r-project.org mailing list
    >> https://stat.ethz.ch/mailman/listinfo/r-devel

    > -- 
    > Peter Dalgaard, Professor,
    > Center for Statistics, Copenhagen Business School
    > Solbjerg Plads 3, 2000 Frederiksberg, Denmark
    > Phone: (+45)38153501
    > Office: A 4.23
    > Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com

    > ______________________________________________
    > R-devel at r-project.org mailing list
    > https://stat.ethz.ch/mailman/listinfo/r-devel



[Rd] problem with pipes, textConnection and read.dcf
Martin Maechler