Blog

quick sort

2022-04-19T08:50:05+00:00

When haskellers say they can implement quick sort in just 2 loc:

qsort [] = []
qsort (x:xs) = qsort [a | a <- xs, a <= x] ++ [x] ++ qsort [a | a <- xs, a > x]

Pythoner smiles:

def qsort(x=[], *xs):
	return x and (qsort(*[a for a in xs if a < x]) + [x] + qsort(*[b for b in xs if b >=x]))
# (x != 0) call with arg destructuring: qsort(*[3, 1, 2])

For linked list sort, we don’t have to do inplace swaping, this is alright. Argument destructuring is used to imitate haskell pattern matching, and here is a real pattern matching version (py3.10):

def qsort(xs):
    match xs:
        case []:
            return []
        case [x, *rest]:
            return qsort([a for a in rest if a < x]) + [x] + qsort([b for b in rest if b >=x])

Still concise, power of multi paradigm language!

Add toggle switch for everything to your Windows desktop

2022-02-16T10:56:55+00:00

The idea is simple:

With powershell script, you can do almost everything on Windows, for instance, start/stop a service:
```
Start-Service -Name FortiSslvpnDaemon
Stop-Service -Name FortiSslvpnDaemon
```
Create a desktop shortcut for that script
You can change the look of shortcut on clicking!! That makes a switch with visual state

Here an example powershell script that start/stop a service:

$shortCutFile = "C:\Users\xxx\Desktop\ToggleFortiVPNDaemon.lnk"
$svcName = "FortiSslvpnDaemon"

function Change-Shortcut-Icon($scFile, $iconNo) {
    $WScriptShell = New-Object -ComObject WScript.Shell
    $shortcut = $WScriptShell.CreateShortcut($scFile)
    $shortcut.IconLocation = "C:\Windows\System32\imageres.dll, $iconNo"
    $shortcut.Save()
}

$svc = Get-Service -Name $svcName
if ($svc.Status -eq 'Running') {
    Stop-Service -Name $svcName
    echo "stoped"
    Change-Shortcut-Icon $shortCutFile 26
} elseif ($svc.Status -eq 'Stopped') {
    Start-Service -Name $svcName
    echo "started"
    Change-Shortcut-Icon $shortCutFile 28
}

Store this script as ToggleFortiVPNDaemon.ps1 somewhere like C:/myscripts, and create Desktop shortcut for it, rename the shortcut to ToggleFortiVPNDaemon.

To run the shortcut as Admin (required by service commands), open property dialog of the shortcut, in the Target field, add powershell before the script name, and click Advanced button, check the Run as Admin.

Now, double click the Desktop shortcut, after a confirmation for admin permission, the service is under control.

The shortcut icon changes as you click, to reflect the service state, and that’s the fantastic part, let’s examine it a bit more.

The Change-Shortcut-Icon function accepts a $iconNo argument, which is the index into icons in resource file imageres.dll, you can use a separate *.ico file for this, but the builtin icon resource is just easier for maintain, it’s already there.

To view all icons in imageres.dll, I recommand IconViewer, after install, it’s integreted in windows property dialog. In above script, I use number 26 and 28, those are:

red cross icon for Stopped status
green check icon for Running status

But I still don’t know how to get the icon number, the #number shown in IconViewer is not right, I tried it out, tell me if you know how.

I wrote this blog post in markdown without writing markdown

2022-02-11T15:08:00+00:00

Actually, I wrote Org.

Github pages is awesome, with the default supported jekyll, you can’t write in org-mode, some people resort to alternative site generators, like hugo, for a workaround, and here is another way: edit-as-format.

How to use the package

With this package, you can edit one format as another format, in emacs, as long as both format supported by pandoc, like org <-> markdown.

Here’s the steps:

Create this blog post as markdown, open it in emacs. (the parent buffer)
M-x edit-as-format-org will open an org-mode buffer. (the indirect buffer)
Write in this buffer with Org syntax, C-x C-s to commit back to parent buffer.

It works vice versa, in case you want to edit Org files as markdown, M-x edit-as-format choose markdown from the prompt. Or, define your own convenient commands:

(defun edit-org-as-markdown ()
  (interactive)
  (edit-as-format "org" "markdown"))

Why should you use it

What really matters about blogging format, the syntax or storage format? Here is my view:

Factor	Really Matters?
Syntax	Yes
Writing Experience	Yes
Storage file	No

I like Org over markdown, because of the syntax, I like to write slash(/) for italic, which is more intuitive than star(*)
I like Org inside Emacs, it feels soooo good editing Org tables with TAB key
How is the file stored, *.md file or *.org file? pure text? or even binary? Not important, only if it can be edited in emacs with Org syntax

If you agree with me, the hugo solution seems less attractive, you should try edit-as-format ;)

Org mode is such big thing, pandoc might not support all of it’s features, I just show you the most basic ones: emphasis, links, ordered/unordered list, code blocks and tables, that’s great amount for blog posting.

Caution: edit-as-format-org will process the whole buffer if there’s no marked region, for posts with front-matter, mark region to exclude it first.

Setup github pages

2022-02-07T13:12:55+00:00

Install jekyll

apt install ruby ruby-dev
gem install jekyll bundler

Create site

mkdir mysite
jekyll new --skip-bundle .
edit Gemfile, comment out gem "jekyll", uncomment gem "github-pages"

Configure site

_config.yml

defaults:
  - scope:
      path: "" # an empty string here means all files in the project
      type: "posts" # previously `post` in Jekyll 2.2.
    values:
      layout: "post" # use `post` layout for all posts
      comments: true # show disqus comment for all posts
disqus:
  shortname: xxxx # where is it used: minima-theme post template
url: "https://xxx" # disqus `this.page.url` prefix

Update dependency

rm Gemfile.lock
bundle update

Run locally

bundle exec jekyll serve -P 8080

Create post

cd _post
emacs `date -I`-post-name.md

M-x auto-insert

where front matter template is defined as:

(define-auto-insert (rx (seq (= 4 digit) ?- (= 2 digit) ?- (= 2 digit) (one-or-more any) ".md"))
  (lambda ()
    (insert "---\ntitle: ")
    (insert (substring (file-name-base (buffer-name)) 11))
    (insert "\ndate: ")
    (insert (format-time-string "%Y-%m-%d %H:%M:%S %z\n---"))))

Reference

Set up site with jekyll

欢迎访问我的博客!

2017-08-24T01:13:53+00:00

jekyll生成的静态网站，在_post里markdown，上传之后，github服务端会运行jekyll，生成静态网页

_post里markdown命名形式为 YYYY-MM-DD-name-of-post.ext ，markdown文件里需要添加jekyll的 front matter。可以看看这条日志的源码了解 front matter。

Jekyll也提供代码段高亮展示，比如:

def print_hi(name)
  puts "Hi, #{name}"
end
print_hi('Tom')
#=> prints 'Hi, Tom' to STDOUT.

欢迎访问我的github主页