为什么使用宏

 1: (defun prelude-search (query-url prompt)
 2:   "Open the search url constructed with the QUERY-URL.
 3: PROMPT sets the `read-string prompt."
 4:   (browse-url
 5:    (concat query-url
 6:            (url-hexify-string
 7:             (if mark-active
 8:                 (buffer-substring (region-beginning) (region-end))
 9:                 (read-string prompt))))))
10: 
11: (defmacro prelude-install-search-engine (search-engine-name search-engine-url search-engine-prompt);; #1
12:   "Given some information regarding a search engine, install the interactive command to search through them"
13:   `(defun ,(intern (format "prelude-%s" search-engine-name)) ();;#2
14:      ,(format "Search %s with a query or region if any." search-engine-name);;#3
15:      (interactive)
16:      (prelude-search ,search-engine-url ,search-engine-prompt))) ;;#4
17: 
18: (prelude-install-search-engine "google"     "http://www.google.com/search?q="              "Google: ");;#5
19: (prelude-install-search-engine "youtube"    "http://www.youtube.com/results?search_query=" "Search YouTube: ")
20: (prelude-install-search-engine "github"     "https://github.com/search?q="                 "Search GitHub: ")
21: (prelude-install-search-engine "duckduckgo" "https://duckduckgo.com/?t=lm&q="              "Search DuckDuckGo: ")
22: