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Chapter 5: Characters
(make-char
(make-char
(make-char
(make-char
67
97
97
97
97
0)
1)
2)
3)
⇒
⇒
⇒
⇒
#\a
#\M-a
#\C-a
#\C-M-a
char-bits char
procedure+
Returns the exact integer representation of char’s bucky bits. For example,
⇒ 0
(char-bits #\a)
⇒ 1
(char-bits #\m-a)
⇒ 2
(char-bits #\c-a)
⇒ 3
(char-bits #\c-m-a)
char-code char
procedure+
Returns the character code of char, an exact integer. For example,
⇒ 97
(char-code #\a)
⇒ 97
(char-code #\c-a)
char-code-limit
char-bits-limit
variable+
variable+
These variables define the (exclusive) upper limits for the character code and bucky
bits (respectively). The character code and bucky bits are always exact non-negative
integers, and are strictly less than the value of their respective limit variable.
char->integer char
integer->char k
procedure
procedure
char->integer returns the character code representation for char. integer->char
returns the character whose character code representation is k.
In MIT Scheme, if (char-ascii? char) is true, then
(eqv? (char->ascii char) (char->integer char))
However, this behavior is not required by the Scheme standard, and code that depends
on it is not portable to other implementations.
These procedures implement order isomorphisms between the set of characters under
the char<=? ordering and some subset of the integers under the <= ordering. That
is, if
(char<=? a b) ⇒ #t
and
(<= x y) ⇒ #t
and x and y are in the range of char->integer, then
(<= (char->integer a)
⇒ #t
(char->integer b))
(char<=? (integer->char x)
⇒ #t
(integer->char y))
Note: If the argument to char->integer or integer->char is a constant, the compiler will constant-fold the call, replacing it with the corresponding result. This is a
very useful way to denote unusual character constants or ascii codes.
char-integer-limit
variable+
The range of char->integer is defined to be the exact non-negative integers that are
less than the value of this variable (exclusive).