46.5 Looking Up and Expanding Abbreviations

Abbrevs are usually expanded by commands for interactive use, including self-insert-command. This section describes the subroutines used in writing such functions, as well as the variables they use for communication.

Function: abbrev-symbol abbrev &optional table

This function returns the symbol representing the abbrev named abbrev. The value returned is nil if that abbrev is not defined. The optional second argument table is the abbrev table to look it up in. If table is nil, this function tries first the current buffer’s local abbrev table, and second the global abbrev table.

Function: abbrev-expansion abbrev &optional table

This function returns the string that abbrev would expand into (as defined by the abbrev tables used for the current buffer). The optional argument table specifies the abbrev table to use, as in abbrev-symbol.

Command: expand-abbrev

This command expands the abbrev before point, if any. If point does not follow an abbrev, this command does nothing. The command returns t if it did expansion, nil otherwise.

Command: abbrev-prefix-mark &optional arg

Mark current point as the beginning of an abbrev. The next call to expand-abbrev will use the text from here to point (where it is then) as the abbrev to expand, rather than using the previous word as usual.

User Option: abbrev-all-caps

When this is set non-nil, an abbrev entered entirely in upper case is expanded using all upper case. Otherwise, an abbrev entered entirely in upper case is expanded by capitalizing each word of the expansion.

Variable: abbrev-start-location

This is the buffer position for expand-abbrev to use as the start of the next abbrev to be expanded. (nil means use the word before point instead.) abbrev-start-location is set to nil each time expand-abbrev is called. This variable is also set by abbrev-prefix-mark.

Variable: abbrev-start-location-buffer

The value of this variable is the buffer for which abbrev-start-location has been set. Trying to expand an abbrev in any other buffer clears abbrev-start-location. This variable is set by abbrev-prefix-mark.

Variable: last-abbrev

This is the abbrev-symbol of the last abbrev expanded. This information is left by expand-abbrev for the sake of the unexpand-abbrev command.

Variable: last-abbrev-location

This is the location of the last abbrev expanded. This contains information left by expand-abbrev for the sake of the unexpand-abbrev command.

Variable: last-abbrev-text

This is the exact expansion text of the last abbrev expanded, after case conversion (if any). Its value is nil if the abbrev has already been unexpanded. This contains information left by expand-abbrev for the sake of the unexpand-abbrev command.

Variable: pre-abbrev-expand-hook

This is a normal hook whose functions are executed, in sequence, just before any expansion of an abbrev. See Hooks. Since it is a normal hook, the hook functions receive no arguments. However, they can find the abbrev to be expanded by looking in the buffer before point.

The following sample code shows a simple use of pre-abbrev-expand-hook. If the user terminates an abbrev with a punctuation character, the hook function asks for confirmation. Thus, this hook allows the user to decide whether to expand the abbrev, and aborts expansion if it is not confirmed.

(add-hook 'pre-abbrev-expand-hook 'query-if-not-space)

;; This is the function invoked by pre-abbrev-expand-hook.

;; If the user terminated the abbrev with a space, the function does
;; nothing (that is, it returns so that the abbrev can expand).  If the
;; user entered some other character, this function asks whether
;; expansion should continue.

;; If the user answers the prompt with y, the function returns
;; nil (because of the not function), but that is
;; acceptable; the return value has no effect on expansion.

(defun query-if-not-space ()
  (if (/= ?\  (preceding-char))
      (if (not (y-or-n-p "Do you want to expand this abbrev? "))
          (error "Not expanding this abbrev"))))