company-mode の backend を書く

一番シンプルなものはこういう感じになる.

(require 'cl-lib)

(defvar company-example-source
'("newton" "gauss" "euler" "cauchy"))

(defun company-example (command &optional arg &rest ignored)
  (interactive (list 'interactive))
  (cl-case command
    (interactive (company-begin-backend 'company-example))
    (prefix (and (eq major-mode 'fundamental-mode)
                 (company-grab-symbol)))
    (candidates
     (cl-remove-if-not (lambda (c) (string-prefix-p arg c)) company-example-source)))

適当な補完候補のリストを作ってやって company の backend の関数を書く. 関数名(company-example)と major-mode(fundamental-mode)は好みのものにすれば良い.

あとはバックエンドを追加してやればいい.

(add-to-list 'company-backends 'company-example)