readLines interaction with gsub different in R-dev

I think the problem in R-devel happens when there are non-ASCII characters
in any
of the strings passed to gsub.

txt <- vapply(list(as.raw(c(0x41, 0x6d, 0xc3, 0xa9, 0x6c, 0x69, 0x65)),
as.raw(c(0x41, 0x6d, 0x65, 0x6c, 0x69, 0x61))), rawToChar, "")
txt
#[1] "Am?lie" "Amelia"
Encoding(txt)
#[1] "unknown" "unknown"
gsub(perl=TRUE, "(\\w)(\\w)", "<\\L\\1\\U\\2>", txt)
#[1] "<a" "<a"
gsub(perl=TRUE, "(\\w)(\\w)", "<\\L\\1\\U\\2>", txt[1])
#[1] "<a"
gsub(perl=TRUE, "(\\w)(\\w)", "<\\L\\1\\U\\2>", txt[2])
#[1] "<aM><eL><iA>"

I can change the Encoding to "latin1" or "UTF-8" and get similar results
from gsub.


Bill Dunlap
TIBCO Software
wdunlap tibco.com

On Sat, Feb 17, 2018 at 7:35 AM, Hugh Parsonage <hugh.parsonage at gmail.com>
wrote:

| Confirmed for R-devel (current) on Ubuntu 17.10.  But ... isn't the
regexp
| you use wrong, ie isn't R-devel giving the correct answer?

No, I don't think R-devel is correct (or at least consistent with the
documentation). My interpretation of gsub("(\\w)", "\\U\\1", entry,
perl = TRUE) is "Take every word character and replace it with itself,
converted to uppercase."

Perhaps my example was too minimal. Consider the following:

R> gsub("(\\w)", "\\U\\1", entry, perl = TRUE)
[1] "A"

R> gsub("(\\w)", "\\1", entry, perl = TRUE)
[1] "author: Am?lie"   # OK, but very different to 'A', despite only
not specifying uppercase

R> gsub("(\\w)", "\\U\\1", "author: Amelie", perl = TRUE)
[1] "AUTHOR: AMELIE"  # OK, but very different to 'A',

R> gsub("^(\\w+?): (\\w)", "\\U\\1\\E: \\2", entry, perl = TRUE)
  "AUTHOR"  # Where did everything after the first group go?

I should note the following example too:
R> gsub("(\\w)", "\\U\\1", entry, perl = TRUE, useBytes = TRUE)
[1] "AUTHOR: AM??LIE"  # latin1 encoding


A call to `readLines` (possibly `scan()` and `read.table` and friends)
is essential.




On 18 February 2018 at 02:15, Dirk Eddelbuettel <edd at debian.org> wrote:

On 17 February 2018 at 21:10, Hugh Parsonage wrote:
| I was told to re-raise this issue with R-dev:
|
| In the documentation of R-dev and R-3.4.3, under ?gsub
|
| > replacement
| >    ... For perl = TRUE only, it can also contain "\U" or "\L" to

convert the rest of the replacement to upper or lower case and "\E" to end
case conversion.

|
| However, the following code runs differently:
|
| tempf <- tempfile()
| writeLines(enc2utf8("author: Am?lie"), con = tempf, useBytes = TRUE)
| entry <- readLines(tempf, encoding = "UTF-8")
| gsub("(\\w)", "\\U\\1", entry, perl = TRUE)
|
|
| "AUTHOR: AM?LIE"  # R-3.4.3
|
| "A"                              # R-dev

Confirmed for R-devel (current) on Ubuntu 17.10.  But ... isn't the

regexp

you use wrong, ie isn't R-devel giving the correct answer?

R> tempf <- tempfile()
R> writeLines(enc2utf8("author: Am?lie"), con = tempf, useBytes = TRUE)
R> entry <- readLines(tempf, encoding = "UTF-8")
R> gsub("(\\w)", "\\U\\1", entry, perl = TRUE)
[1] "A"
R> gsub("(\\w+)", "\\U\\1", entry, perl = TRUE)
[1] "AUTHOR"
R> gsub("(.*)", "\\U\\1", entry, perl = TRUE)
[1] "AUTHOR: AM?LIE"
R>

Dirk

--
http://dirk.eddelbuettel.com | @eddelbuettel | edd at debian.org

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