6.11 Regexp Quantifiers

20180608 Quantifiers are used to match repitition of a pattern within a string. The following table shows a list of quantifiers.

% latex table generated in R 4.0.5 by xtable 1.8-4 package % Mon Apr 19 09:37:54 2021

Some examples will illustrate.

s <- c("aaab", "abb", "bc", "abbcd", "bbbc", "abab", "caa")
grep(pattern="ab*b", s, value=TRUE)
## [1] "aaab"  "abb"   "abbcd" "abab"
grep(pattern="abbc?", s, value=TRUE)
## [1] "abb"   "abbcd"
grep(pattern="b{2,}?", s, value=TRUE)
## [1] "abb"   "abbcd" "bbbc"

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