— 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

This is empty, because ASCII has no titlecase characters.

— Scheme Variable: char-set:letter
— C Variable: scm_char_set_letter

All letters, e.g. the union of char-set:lower-case and char-set:upper-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, that is #\space and #\tab.

— Scheme Variable: char-set:iso-control
— C Variable: scm_char_set_iso_control

The ISO control characters with the codes 0–31 and 127.

— Scheme Variable: char-set:punctuation
— C Variable: scm_char_set_punctuation

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

— Scheme Variable: char-set:symbol
— C Variable: scm_char_set_symbol

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:full
— C Variable: scm_char_set_full

This character set contains all possible characters.