6.6.4.6 Standard Character Sets

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 upon a setlocale call. They contain characters from the whole range of Unicode code points. For instance, char-set:letter contains about 100,000 characters.

Scheme Variable: char-set:lower-case

C Variable: scm_char_set_lower_case

All lower-case characters.

Scheme Variable: char-set:upper-case

C Variable: scm_char_set_upper_case

All upper-case characters.

Scheme Variable: char-set:title-case

C Variable: scm_char_set_title_case

All single characters that function as if they were an upper-case letter followed by a lower-case letter.

Scheme Variable: char-set:letter

C Variable: scm_char_set_letter

All letters. This includes char-set:lower-case, char-set:upper-case, 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.

Scheme Variable: char-set:digit

C Variable: scm_char_set_digit

All digits.

Scheme Variable: char-set:letter+digit

C Variable: scm_char_set_letter_and_digit

The union of char-set:letter and char-set:digit.

Scheme Variable: char-set:graphic

C Variable: scm_char_set_graphic

All characters which would put ink on the paper.

Scheme Variable: char-set:printing

C Variable: scm_char_set_printing

The union of char-set:graphic and char-set:whitespace.

Scheme Variable: char-set:whitespace

C Variable: scm_char_set_whitespace

All whitespace characters.

Scheme Variable: char-set:blank

C Variable: scm_char_set_blank

All horizontal whitespace characters, which notably includes #\space and #\tab.

Scheme Variable: char-set:iso-control

C Variable: scm_char_set_iso_control

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).

Scheme Variable: char-set:punctuation

C Variable: scm_char_set_punctuation

All punctuation characters, such as the characters !"#%&'()*,-./:;?@[\\]_{}

Scheme Variable: char-set:symbol

C Variable: scm_char_set_symbol

All symbol characters, such as the characters $+<=>^`|~.

Scheme Variable: char-set:hex-digit

C Variable: scm_char_set_hex_digit

The hexadecimal digits 0123456789abcdefABCDEF.

Scheme Variable: char-set:ascii

C Variable: scm_char_set_ascii

All ASCII characters.

Scheme Variable: char-set:empty

C Variable: scm_char_set_empty

The empty character set.

Scheme Variable: char-set:designated

C Variable: scm_char_set_designated

This character set contains all designated code points. This includes all the code points to which Unicode has assigned a character or other meaning.

Scheme Variable: char-set:full

C Variable: scm_char_set_full

This character set contains all possible code points. This includes both designated and reserved code points.