similar to: Parsing regular expressions differently - feature request

I thought that I can use metacharacters such as \w to match word characters with one backslash. But for some reason, I need to include two backslashes. > grepl(pattern='\w', x="what") Error: '\w' is an unrecognized escape in character string starting "\w" > grepl(pattern='\\w', x="what") [1] TRUE I can't find the reason for this

Hello, I have several strings where I am trying to eliminate the period and everything after the period, using a regular expression. However, I am having trouble getting this to work. > x = "wa.w" > gsub(x, "\..*", "", perl=TRUE) [1] "" Warning messages: 1: '\.' is an unrecognized escape in a character string 2: unrecognized escape removed

Hi, I guess the backslash should not be used as the separator for strsplit() in compareVersion(), because the period in [.] is no longer a metacharacter (no need to "escape" it using a backslash): https://github.com/wch/r-source/blob/trunk/src/library/utils/R/packages.R#L866-L867 > compareVersion function (a, b) { .... a <- as.integer(strsplit(a, "[\\.-]")[[1L]])

Why sometimes one has to put a double backslash in regular expressions, but often simple backslashes work too? Is only a \ required for giving a metacharacter its usual meaning? --------------------------------------- u=grep('\\{[\\-u]x',a,perl=T) # equivalent to u=grep('\{[\-u]x',a,perl=T) # but u=grep('\w',a,perl=T) # is not correct and requires

Hi folks, Can anyone enlighten me as to why I get the following when I search for ".csv" at the end of a string? > grep("\.csv$","Blah.csv",value=TRUE) [1] "Blah.csv" Warning messages: 1: '\.' is an unrecognized escape in a character string 2: unrecognized escape removed from "[\.]csv$" R reference for regular expressions says

Hi all, > diff_operator <- "\\(" > strsplit(cond, diff_operator) [[1]] [1] "andsin" "log_angle_1_4)" > diff_operator <- "\\sin(" > strsplit(cond, diff_operator) Error in strsplit(cond, diff_operator) : invalid regular expression '\sin(', reason 'Missing ')'' When I am going to split with "("

Full_Name: FAN Version: 2.4.0 OS: Windows Submission from: (NULL) (159.50.101.9) These are expected: > grep("[\-|c]", c("a-a","b")) [1] 1 > gsub("[\-|c]", "&", c("a-a","b")) [1] "a&a" "b" but these are strange: > grep("[d|\-|c]", c("a-a","b")) integer(0)

Hi there, ubuntu 18.04.2, trying to compile R-devel 3.6.0, svn 76155. I am having difficulty compiling R. I think I have pcre installed correctly: OK~/Downloads/R-devel pcretest -C PCRE version 8.41 2017-07-05 Compiled with 8-bit support UTF-8 support No Unicode properties support No just-in-time compiler support Newline sequence is LF \R matches all Unicode newlines Internal

Hi, I would really like to have a way to split long string literals across multiple lines in R. Currently, if a string literal spans multiple lines, there is no way to inhibit the introduction of newline characters: > "aaa + bbb" [1] "aaa\nbbb" If a line ends with a backslash, it is just ignored: > "aaa\ + bbb" [1] "aaa\nbbb" We could use

Dear All, Perhaps this should go in r-package-devel, but I suspect that this is going to turn into a feature request, and I want to run it by the list before filing it in the Bugzilla. I would like to specify a long string literal without making the line of code too long. In R, "abc def" yields the string "abc\def", and, as far as I can tell, there is no mechanism for

Hi, I am trying to use sub, regexpr on expressions like log(D) ~ log(N)+I(log(N)^2)+log(t) being a model specification. The aim is to produce: "ln D ~ ln N + ln^2 N + ln t" The variable names N, t may change, the number of terms too. I succeded only partially, help on regular expressions is hard to understand for me, examples on my case are rare. The help page on R-help

Tomas, Here is a good example of where this functionality would be useful: https://github.com/R-ArcGIS/arcgislayers/blob/2b29f4c254e7e5a1dadce8d4b0015a70dfae39d4/R/arc-open.R#L19-L56 In order to prevent R CMD check notes I have to use `paste0()` to concatenate long URLs. If we were able to use `\` to separate the string across multiple lines, it would make the solution much nicer! On Mon, Jun

Railsters: ActiveRecord''s validation system puts other database systems to shame. However, the newbies might not know how to write a regexp that excludes a match, instead of tests for it. Understand - I''m just asking this question to help them. I have been using Regexps since ''grep'' on Xenix! But the newbies here might not know how to do this:

One could also argue that paste0("a", "b", "c") is a function call that needs to be evaluated at runtime, whereas "abc" is a string constant understood by the parser, and often also language agnostic. I'd assume compilers and code- and text-search tools do a better job with the latter. /Henrik On Mon, Jun 2, 2025 at 2:18?PM Josiah Parry

I suppose taste is learned as well. It does feel quite odd that the best way to define a long string without a note or text wrapping is by being creative with functions. This is valid in Python, Julia, and Rust (if you add `let` and a terminating semi-colon): my_str = "part1\ part2\ part2" I don't think it is abnormal to expect or desire this type of functionality in our favorite

On 6/2/25 17:37, Josiah Parry wrote: > Tomas, > > Here is a good example of where this functionality would be useful: > https://github.com/R-ArcGIS/arcgislayers/blob/2b29f4c254e7e5a1dadce8d4b0015a70dfae39d4/R/arc-open.R#L19-L56 > > In order to prevent R CMD check notes I have to use `paste0()` to > concatenate long URLs. If we were able to use `\` to > separate the string

On 5/28/25 04:15, Pavel Krivitsky via R-devel wrote: > Dear All, > > Perhaps this should go in r-package-devel, but I suspect that this is > going to turn into a feature request, and I want to run it by the list > before filing it in the Bugzilla. > > I would like to specify a long string literal without making the line > of code too long. In R, > > "abc >

Ok, I''m hoping this won''t be a forehead slapper, but take a look at this code: physician.name.sub(/''/, "\\''") I''m trying to substitute a single quote with a backslash and a single quote. This seems pretty simple right? Well, someone kick me and tell me why it''s not :) Here''s what I''m getting if the

Like Tomas, I find the paste0 readability to be **much** better, partly because it allows for better indentation (as Tomas pointed out). Perhaps a pointless email, but sometimes - for these subjective issues - it is worthwhile to point out a difference in opinion. Best, Kasper On Mon, Jun 2, 2025 at 12:27?PM Tomas Kalibera <tomas.kalibera at gmail.com> wrote: > > On 6/2/25 17:37,

> On 3 Jun 2025, at 09:34, Henrik Bengtsson <henrik.bengtsson at gmail.com> wrote: > > One could also argue that paste0("a", "b", "c") is a function call that needs to be evaluated at runtime, whereas "abc" is a string constant understood by the parser, and often also language agnostic. I'd assume compilers and code- and text-search tools