Go to the previous, next section.
MIT Scheme's character-set abstraction is used to represent groups of characters, such as the letters or digits. Character sets may contain only ASCII characters; in the future this may be changed to allow the full range of characters.
There is no meaningful external representation for character sets; use
char-set-members to examine their contents. There is (at
present) no specific equivalence predicate for character sets; use
equal? for this purpose.
Returns #t if object is a character set; otherwise returns
#f.(7)
variable+: char-set:upper-case
variable+: char-set:lower-case
variable+: char-set:alphabetic
variable+: char-set:alphanumeric
variable+: char-set:whitespace
variable+: char-set:not-whitespace
variable+: char-set:not-graphic
These variables contain predefined character sets.
To see the contents of one of these sets, use char-set-members.
Alphabetic characters are the 52 upper and lower case letters.
Numeric characters are the 10 decimal digits. Alphanumeric
characters are those in the union of these two sets. Whitespace
characters are #\space, #\tab, #\page,
#\linefeed, and #\return. Graphic characters are
the printing characters and #\space. Standard characters
are the printing characters, #\space, and #\newline.
These are the printing characters:
! " # $ % & ' ( ) * + , - . /
0 1 2 3 4 5 6 7 8 9
: ; < = > ? @
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
[ \ ] ^ _ `
a b c d e f g h i j k l m n o p q r s t u v w x y z
{ | } ~
procedure: char-upper-case? char
procedure: char-lower-case? char
procedure: char-alphabetic? char
procedure+: char-alphanumeric? char
procedure: char-whitespace? char
procedure+: char-graphic? char
procedure+: char-standard? object
These predicates are defined in terms of the respective character sets defined above.
procedure+: char-set-members char-set
Returns a newly allocated list of the characters in char-set.
procedure+: char-set-member? char-set char
Returns #t if the char is in char-set; otherwise
returns #f.
Returns a character set consisting of the specified ASCII
characters. With no arguments, char-set returns an empty
character set.
procedure+: chars->char-set chars
Returns a character set consisting of chars, which must be a list
of ASCII characters. This is equivalent to (apply char-set
chars).
procedure+: string->char-set string
Returns a character set consisting of all the characters that occur in string.
procedure+: ascii-range->char-set lower upper
Lower and upper must be exact non-negative integers representing ASCII character codes, and lower must be less than or equal to upper. This procedure creates and returns a new character set consisting of the characters whose ASCII codes are between lower (inclusive) and upper (exclusive).
procedure+: predicate->char-set predicate
Predicate must be a procedure of one argument.
predicate->char-set creates and returns a character set
consisting of the ASCII characters for which predicate is
true.
procedure+: char-set-difference char-set1 char-set2
Returns a character set consisting of the characters that are in char-set1 but aren't in char-set2.
procedure+: char-set-intersection char-set1 char-set2
Returns a character set consisting of the characters that are in both char-set1 and char-set2.
procedure+: char-set-union char-set1 char-set2
Returns a character set consisting of the characters that are in one or both of char-set1 and char-set2.
procedure+: char-set-invert char-set
Returns a character set consisting of the ASCII characters that are not in char-set.
Go to the previous, next section.