— Function: define-category char docstring &optional table

This function defines a new category, with name char and documentation docstring, for the category table table.

Here's an example of defining a new category for characters that have strong right-to-left directionality (see Bidirectional Display) and using it in a special category table. To obtain the information about the directionality of characters, the example code uses the ‘bidi-class’ Unicode property (see bidi-class).

          (defvar special-category-table-for-bidi
            ;;     Make an empty category-table.
            (let ((category-table (make-category-table))
                  ;; Create a char-table which gives the 'bidi-class' Unicode
                  ;; property for each character.
                  (uniprop-table
                   (unicode-property-table-internal 'bidi-class)))
              (define-category ?R "Characters of bidi-class R, AL, or RLO"
                               category-table)
              ;; Modify the category entry of each character whose
              ;; 'bidi-class' Unicode property is R, AL, or RLO --
              ;; these have a right-to-left directionality.
              (map-char-table
               #'(lambda (key val)
                   (if (memq val '(R AL RLO))
                       (modify-category-entry key ?R category-table)))
               uniprop-table)
              category-table))

— Function: category-docstring category &optional table

This function returns the documentation string of category category in category table table.

          (category-docstring ?a)
               ⇒ "ASCII"
          (category-docstring ?l)
               ⇒ "Latin"

— Function: get-unused-category &optional table

This function returns a category name (a character) which is not currently defined in table. If all possible categories are in use in table, it returns nil.

— Function: category-table

This function returns the current buffer's category table.

— Function: category-table-p object

This function returns t if object is a category table, otherwise nil.

— Function: standard-category-table

This function returns the standard category table.

— Function: copy-category-table &optional table

This function constructs a copy of table and returns it. If table is not supplied (or is nil), it returns a copy of the standard category table. Otherwise, an error is signaled if table is not a category table.

— Function: set-category-table table

This function makes table the category table for the current buffer. It returns table.

— Function: make-category-table

This creates and returns an empty category table. In an empty category table, no categories have been allocated, and no characters belong to any categories.

— Function: make-category-set categories

This function returns a new category set—a bool-vector—whose initial contents are the categories listed in the string categories. The elements of categories should be category names; the new category set has t for each of those categories, and nil for all other categories.

          (make-category-set "al")
               ⇒ #&128"\0\0\0\0\0\0\0\0\0\0\0\0\2\20\0\0"

— Function: char-category-set char

This function returns the category set for character char in the current buffer's category table. This is the bool-vector which records which categories the character char belongs to. The function char-category-set does not allocate storage, because it returns the same bool-vector that exists in the category table.

          (char-category-set ?a)
               ⇒ #&128"\0\0\0\0\0\0\0\0\0\0\0\0\2\20\0\0"

— Function: category-set-mnemonics category-set

This function converts the category set category-set into a string containing the characters that designate the categories that are members of the set.

          (category-set-mnemonics (char-category-set ?a))
               ⇒ "al"

— Function: modify-category-entry char category &optional table reset

This function modifies the category set of char in category table table (which defaults to the current buffer's category table). char can be a character, or a cons cell of the form (min . max); in the latter case, the function modifies the category sets of all characters in the range between min and max, inclusive.

Normally, it modifies a category set by adding category to it. But if reset is non-nil, then it deletes category instead.

— Command: describe-categories &optional buffer-or-name

This function describes the category specifications in the current category table. It inserts the descriptions in a buffer, and then displays that buffer. If buffer-or-name is non-nil, it describes the category table of that buffer instead.