Backreferences

Backreferences

Backreferences for replacement operations. These are used by replacement functions such as sub and stri_replace_first_regex, and by the stringi and stringr match functions such as stri_match_first_regex.

Usage

REF1
REF2
REF3
REF4
REF5
REF6
REF7
REF8
REF9
ICU_REF1
ICU_REF2
ICU_REF3
ICU_REF4
ICU_REF5
ICU_REF6
ICU_REF7
ICU_REF8
ICU_REF9

Format

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

References

http://www.regular-expressions.info/backref.html and http://www.rexegg.com/regex-capture.html

See Also

capture, for creating capture groups that can be referred to.

Aliases

• Backreferences
• REF1
• Backreferences
• REF2
• Backreferences
• REF3
• Backreferences
• REF4
• Backreferences
• REF5
• Backreferences
• REF6
• Backreferences
• REF7
• Backreferences
• REF8
• Backreferences
• REF9
• Backreferences
• ICU_REF1
• Backreferences
• ICU_REF2
• Backreferences
• ICU_REF3
• Backreferences
• ICU_REF4
• Backreferences
• ICU_REF5
• Backreferences
• ICU_REF6
• Backreferences
• ICU_REF7
• Backreferences
• ICU_REF8
• Backreferences
• ICU_REF9

Examples

# For R's PCRE and Perl engines
REF1
REF2
# and so on, up to
REF9

# For stringi/stringr's ICU engine
ICU_REF1
ICU_REF2
# and so on, up to
ICU_REF9

# Usage
sub("a(b)c(d)", REF1 %R% REF2, "abcd")
stringi::stri_replace_first_regex("abcd", "a(b)c(d)", ICU_REF1 %R% ICU_REF2)