Create character classes

Source: R/character_class.R

There are multiple ways you can define a character class.

character_class(x)

one_of(...)

any_of(..., type = c("greedy", "lazy", "possessive"))

some_of(..., type = c("greedy", "lazy", "possessive"))

none_of(...)

except_any_of(..., type = c("greedy", "lazy", "possessive"))

except_some_of(..., type = c("greedy", "lazy", "possessive"))

range(start, end)

start:end

exclude_range(start, end)

Arguments

x

text to include in the character class (must be escaped manually)

...

shortcuts, R variables, text, or other rex functions.

type

the type of match to perform.

There are three match types

  1. greedy: match the longest string. This is the default matching type.

  2. lazy: match the shortest string. This matches the shortest string from the same anchor point, not necessarily the shortest global string.

  3. possessive: match and don't allow backtracking

start

beginning of character class

end

end of character class

Functions

  • character_class: explicitly define a character class

  • one_of: matches one of the specified characters.

  • any_of: matches zero or more of the specified characters.

  • some_of: matches one or more of the specified characters.

  • none_of: matches anything but one of the specified characters.

  • except_any_of: matches zero or more of anything but the specified characters.

  • except_some_of: matches one or more of anything but the specified characters.

  • range: matches one of any of the characters in the range.

  • :: matches one of any of the characters in the range.

  • exclude_range: matches one of any of the characters except those in the range.

See also

Other rex: %or%(), capture(), counts, group(), lookarounds, not(), rex(), shortcuts, wildcards

Examples

# grey = gray
re <- rex("gr", one_of("a", "e"), "y")
grepl(re, c("grey", "gray")) # TRUE TRUE
#> [1] TRUE TRUE

# Match non-vowels
re <- rex(none_of("a", "e", "i", "o", "u"))
# They can also be in the same string
re <- rex(none_of("aeiou"))
grepl(re, c("k", "l", "e")) # TRUE TRUE FALSE
#> [1]  TRUE  TRUE FALSE

# Match range
re <- rex(range("a", "e"))
grepl(re, c("b", "d", "f")) # TRUE TRUE FALSE
#> [1]  TRUE  TRUE FALSE

# Explicit creation
re <- rex(character_class("abcd\\["))
grepl(re, c("a", "d", "[", "]")) # TRUE TRUE TRUE FALSE
#> [1]  TRUE  TRUE  TRUE FALSE