2.9.3.7 Standard character sets

Several character sets are predefined for convenience:

char-set:lower-case

Lower–case letters.

char-set:upper-case

Upper–case letters.

char-set:title-case

Title–case letters.

char-set:letter

Letters.

char-set:digit

Digits.

char-set:letter+digit

Letters and digits.

char-set:graphic

Printing characters except spaces.

char-set:printing

Printing characters including spaces.

char-set:whitespace

Whitespace characters.

char-set:iso-control

The ISO control characters.

char-set:punctuation

Punctuation characters.

char-set:symbol

Symbol characters.

char-set:hex-digit

A hexadecimal digit: 0-9, A-F, a-f.

char-set:blank

Blank characters, horizontal whitespace.

char-set:ascii

All characters in the ASCII set.

char-set:empty

Empty set.

char-set:full

All characters.

Note that there may be characters in char-set:letter that are neither upper or lower case. A “graphic character” is one that would put ink on your page.