In order to make the use of the character set data type and procedures useful, several predefined character set variables exist.
These character sets are locale independent and are not recomputed
setlocale call. They contain characters from the whole
range of Unicode code points. For instance,
contains about 100,000 characters.
All lower-case characters.
All upper-case characters.
All single characters that function as if they were an upper-case letter followed by a lower-case letter.
All letters. This includes
char-set:title-case, and many
letters that have no case at all. For example, Chinese and Japanese
characters typically have no concept of case.
The union of
All characters which would put ink on the paper.
The union of
All whitespace characters.
All horizontal whitespace characters, which notably includes
The ISO control characters are the C0 control characters (U+0000 to U+001F), delete (U+007F), and the C1 control characters (U+0080 to U+009F).
All punctuation characters, such as the characters
All symbol characters, such as the characters
The hexadecimal digits
All ASCII characters.
The empty character set.
This character set contains all designated code points. This includes all the code points to which Unicode has assigned a character or other meaning.
This character set contains all possible code points. This includes both designated and reserved code points.