Helpful string constants.

Constants

let ascii_letters = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'

let ascii_lowercase = 'abcdefghijklmnopqrstuvwxyz'

let ascii_uppercase = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'

let digits = '0123456789'

let hexdigits = '0123456789abcdefABCDEF'

let octdigits = '01234567'

let printable = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!"#$%&\'()*+,-./:;<=>?@[\\]^_`{|}~\t\n\v\f\r '

let punctuation = '!"#$%&\'()*+,-./:;<=>?@[\\]^_`{|}~'

let whitespace = '\t\n\v\f\r '