Convert numbers, alphabets, and some other characters (except punctuations) from Zenkaku format to Hankaku format.

ZenHan.el

;; checked under Emacs24
(defun eisuu-hankaku-region (from to &optional ascii-only)
  "Convert JP `zenkaku' eisuu ([A-Z0-9a-z]) and some other chars, which does
not include punctuation chars, in the region to `hankaku' chars.
`Zenkaku' chars belong to `japanese-jisx0208'
`Hankaku' chars belong to `ascii' or `japanese-jisx0201-kana'.
NOTE: Optional argument ASCII-ONLY is ignored here."
  (interactive "r\nP")
  (save-restriction
    (narrow-to-region from to)
    (save-excursion
      (goto-char (point-min))
      (while (re-search-forward "\\cj" nil t)
	(let* ((zenkaku (preceding-char))
	       (hankaku 
;; original
;	        (or (and (not ascii-only)
;			 (get-char-code-property zenkaku 'jisx0201))
;		    (get-char-code-property zenkaku 'ascii))

		;; patch for japanese-hankaku-region
		;;   printable ascii chars except [A-Z0-9a-z] are:
		;;   ！￥″＃＄％＆′（）＊＋，ー．／：；＜＝＞？＠［￥］＾＿’｛｜｝〜
		;;   (in hankaku, !\"#$%&'()*+,-./:;<=>?@[\]^_'{|}~)

		;; always ascii-only, but punctuations should be omitted
		(if (member zenkaku '(?、 ?。 ?， ?． ?〜 ?ー))
		    nil
		    (get-char-code-property zenkaku 'ascii))
		 ))
	  (if hankaku
	      (japanese-replace-region (match-beginning 0) (match-end 0)
				       hankaku)))))))