Character classes

• character class or set []: match any character in a set.
• construct your own sets with []
  • [abc] matches “a”, “b”, or “c”
  • [^abc] matches any character except “a”, “b”, or “c”.
• two other characters that have special meaning inside of []:
  • - defines a range, e.g., [a-z] matches any lower case letter and [0-9] matches any number.
  • \ escapes special characters, so [\^\-\]] matches ^, -, or ].

x <- "abcd ABCD 12345 -!@#%."
str_view(x, "[abc]+")

## [1] │ <abc>d ABCD 12345 -!@#%.

str_view(x, "[a-z]+")

## [1] │ <abcd> ABCD 12345 -!@#%.

str_view(x, "[^a-z0-9]+")

## [1] │ abcd< ABCD >12345< -!@#%.>

# You need an escape to match characters that are otherwise
# special inside of []
str_view("a-b-c", "[a-c]")

## [1] │ <a>-<b>-<c>

str_view("a-b-c", "[a\\-c]")

## [1] │ <a><->b<-><c>