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A char-table is much like a vector, except that it is indexed by
character codes. Any valid character code, without modifiers, can be
used as an index in a char-table. You can access a char-table's
elements with aref
and aset
, as with any array. In
addition, a char-table can have extra slots to hold additional
data not associated with particular character codes. Char-tables are
constants when evaluated.
Each char-table has a subtype which is a symbol. The subtype
has two purposes: to distinguish char-tables meant for different uses,
and to control the number of extra slots. For example, display tables
are char-tables with display-table
as the subtype, and syntax
tables are char-tables with syntax-table
as the subtype. A valid
subtype must have a char-table-extra-slots
property which is an
integer between 0 and 10. This integer specifies the number of
extra slots in the char-table.
A char-table can have a parent, which is another char-table. If
it does, then whenever the char-table specifies nil
for a
particular character c, it inherits the value specified in the
parent. In other words, (aref
char-table c)
returns
the value from the parent of char-table if char-table itself
specifies nil
.
A char-table can also have a default value. If so, then
(aref
char-table c)
returns the default value
whenever the char-table does not specify any other non-nil
value.
Return a newly created char-table, with subtype subtype. Each element is initialized to init, which defaults to
nil
. You cannot alter the subtype of a char-table after the char-table is created.There is no argument to specify the length of the char-table, because all char-tables have room for any valid character code as an index.
This function sets the default value of char-table to new-default.
There is no special function to access the default value of a char-table. To do that, use
(char-table-range
char-tablenil)
.
This function returns the parent of char-table. The parent is always either
nil
or another char-table.
This function sets the parent of char-table to new-parent.
This function returns the contents of extra slot n of char-table. The number of extra slots in a char-table is determined by its subtype.
This function stores value in extra slot n of char-table.
A char-table can specify an element value for a single character code; it can also specify a value for an entire character set.
This returns the value specified in char-table for a range of characters range. Here are the possibilities for range:
nil
- Refers to the default value.
- char
- Refers to the element for character char (supposing char is a valid character code).
- charset
- Refers to the value specified for the whole character set charset (see Character Sets).
- generic-char
- A generic character stands for a character set; specifying the generic character as argument is equivalent to specifying the character set name. See Splitting Characters, for a description of generic characters.
This function sets the value in char-table for a range of characters range. Here are the possibilities for range:
nil
- Refers to the default value.
t
- Refers to the whole range of character codes.
- char
- Refers to the element for character char (supposing char is a valid character code).
- charset
- Refers to the value specified for the whole character set charset (see Character Sets).
- generic-char
- A generic character stands for a character set; specifying the generic character as argument is equivalent to specifying the character set name. See Splitting Characters, for a description of generic characters.
This function calls function for each element of char-table. function is called with two arguments, a key and a value. The key is a possible range argument for
char-table-range
—either a valid character or a generic character—and the value is(char-table-range
char-table key)
.Overall, the key-value pairs passed to function describe all the values stored in char-table.
The return value is always
nil
; to make this function useful, function should have side effects. For example, here is how to examine each element of the syntax table:(let (accumulator) (map-char-table #'(lambda (key value) (setq accumulator (cons (list key value) accumulator))) (syntax-table)) accumulator) => ((475008 nil) (474880 nil) (474752 nil) (474624 nil) ... (5 (3)) (4 (3)) (3 (3)) (2 (3)) (1 (3)) (0 (3)))