Optionally match an expression.

Source: R/rules.R

This expression uses a quantifier ? to optionally match things. Specifically, the question mark makes the preceding token in the regular expression optional.

rx_maybe(.data = NULL, value)

Arguments

.data

Expression to append, typically pulled from the pipe %>%
value

Expression to optionally match

References

Quantifiers: https://www.regular-expressions.info/optional.html

Examples

rx_maybe(value = "abc")
#> [1] "(abc)?"

# create expression
x <- rx() %>%
  rx_start_of_line() %>%
  rx_maybe("abc") %>%
  rx_end_of_line(enable = FALSE)

grepl(x, "xyz") # should be true
#> [1] TRUE