SpecialCharacters: Special characters

In rebus.base: Core Functionality for the 'rebus' Package

Description

Constants to match special characters.

Usage

BACKSLASH

CARET

DOLLAR

DOT

PIPE

QUESTION

STAR

PLUS

OPEN_PAREN

CLOSE_PAREN

OPEN_BRACKET

CLOSE_BRACKET

OPEN_BRACE

Format

An object of class regex (inherits from character) of length 1.

References

http://www.regular-expressions.info/characters.html

See Also

escape_special for the functional form, CharacterClasses for regex metacharacters, Anchors for constants to match the start/end of a string, WordBoundaries for contants to match the start/end of a word.

Examples

BACKSLASH
CARET
DOLLAR
DOT
PIPE
QUESTION
STAR
PLUS
OPEN_PAREN
CLOSE_PAREN
OPEN_BRACKET
CLOSE_BRACKET
OPEN_BRACE

# Usage
x <- "\\^$."
rx <- BACKSLASH %R% CARET %R% DOLLAR %R% DOT
stringi::stri_detect_regex(x, rx)
# No escapes - these chars have special meaning inside regex
stringi::stri_detect_regex(x, x)

# Usually closing brackets can be matched without escaping
stringi::stri_detect_regex("]", "]")
# If you want to match a closing bracket inside a character class
# the closing bracket must be placed first
(rx <- char_class("]a"))
stringi::stri_detect_regex("]", rx)
# ICU and Perl also allows you to place the closing bracket in
# other positions if you escape it
(rx <- char_class("a", CLOSE_BRACKET))
stringi::stri_detect_regex("]", rx)
grepl(rx, "]", perl = TRUE)
# PCRE does not allow this
grepl(rx, "]")

Example output

<regex> \\
<regex> \^
<regex> \$
<regex> \.
<regex> \|
<regex> \?
<regex> \*
<regex> \+
<regex> \(
<regex> \)
<regex> \[
<regex> \]
<regex> \{
[1] TRUE
[1] FALSE
[1] TRUE
<regex> []a]
[1] TRUE
<regex> [a\]]
[1] TRUE
[1] TRUE
[1] FALSE

rebus.base documentation built on May 2, 2019, 5:14 a.m.