SpaceEmacs Rock Day9 学习笔记

SpaceEmacs Rock Day9 学习笔记

SpaceEmacs Rock Day9 学习笔记

1 SpaceEmacs Rock Day9 学习笔记

Topic: Macro and the-package

1.1 What is macro?

Code which generate code? 

(defmacro inc (var)
  (list 'setq var (list '1+ var)))

(setq my-var 1)
(setq my-var (+ 1 my-var))

See the macro expand 

(setq my-var 1)
(macroexpand '(inc my-var))

Write macro is almost the same as writing function in elisp.

2 What's the different between function and macro?

  1. Evaluation: the macro arguments are the actual expressions apperaring in the macro call.
  2. Expansion: the value returned by the macro body is an alternate Lisp expression, also known as

2.1 back quote matters

(with-eval-after-load 'smartparens
  (sp-local-pair 'emacs-lisp-mode "`" nil :actions nil))

example,quote and back quote 

(defun my-print (number)
  (message "This is a number: %d" number))

(my-print 2)

(my-print (+ 2 3))

;; return a expression
(quote (+ 1 1))

(defmacro my-print-2 (number)
  `(message "This is a number: %d", number))

(my-print-2 2)

(my-print-2 (+ 2 3))

(defmacro inc2 (var1 var2)
  (list 'progn (list 'inc var1) (list 'inc var2)))

(macroexpand '(inc2 my-var my-var))
(macroexpand-all '(inc2 my-var my-var))

3 Why Macro?

3.1 A more useful example of Elisp macro

(defun prelude-search (query-url prompt)
  "Open the search url constructed with the QUERY URL,
PROMPT set the `read-string prompt."
  (browse-url
   (concat query-url
           (url-hexify-string
            (if mark-active
                (buffer-substring (region-beginning) (region-end))
              (read-string prompt))))))
(defmacro prelude-install-search-engine (search-engine-name search-engine-url search-engine-prompt)
  "Given some information regarding a search engine, install the interactive command to search through them"
  `(defun ,(intern (format "prelude-%s" search-engine-name)) ()
     ,(format "Search %s with a query or region if any." search-engine-name)
     (interactive)
     (prelude-search ,search-engine-url, search-engine-prompt)))

(prelude-install-search-engine "google" "http://google.com/seearch?q=" "Google: ")
(prelude-install-search-engine "youtube" "http://youtube.com/results?search_query=" "Search YouTube: ")
(prelude-install-search-engine "github" "https://github.com/search?q=" "Search GitHub:")
(prelude-install-search-engine "duckduckgo" "https://duckduckgo.com/?t=lm&q=" "Search Duckduckgo: ")
(macroexpand '(prelude-install-search-engine "google" "http://google.com/seearch?q=" "Google: "))

4 Use package and basic usage

  1. a more safe require
  2. group config into one place
  3. autoload and bind keys easily
  4. make your config local faster
  5. and more? SpaceEmacs use it a lot
(use-package color-moccur
  :commands (isearch-moccur isearch-all)
  :bind (("M-s O" . moccur)
         :map isearch-mode-map
         ("M-s o" . isearch-moccur)
         ("M-s o" . isearch-moccur-all))
  :init
  (setq isearch-lazy-highlight t)
  :config
  (use-package moccur-edit))

5 brain Training

(defmacro defsynonym (old-name new-name)
  `(defmacro ,new-name (&rest args)
     `(, ',old-name ,@args)))

more discussion: https://emacs-china.org/t/lisp/357

Date: 2018-10-27 21:12

Author: devinkin

Created: 2018-10-27 六 21:32

Validate

posted @ 2018-10-27 21:13  EmacsDevinkin  阅读(226)  评论(0)  编辑  收藏  举报