Regex flags, comments

• comments = TRUE tweaks the pattern language to ignore spaces and new lines, as well as everything after #.
• use comments and whitespace to make complex regular expressions more understandable
• using comments and want to match a space, newline, or #, you’ll need to escape it with \.

phone <- regex(
  r"(
    \(?     # optional opening parens
    (\d{3}) # area code
    [)\-]?  # optional closing parens or dash
    \ ?     # optional space
    (\d{3}) # another three numbers
    [\ -]?  # optional space or dash
    (\d{4}) # four more numbers
  )", 
  comments = TRUE
)

str_extract(c("514-791-8141", "(123) 456 7890", "123456"), phone)

## [1] "514-791-8141"   "(123) 456 7890" NA