• FreeIPA in AWS EC2

    Posted on: Thu, 12/07/2017 - 23:34 By: Huahai

    Show how to install and configure freeIPA server and clients in AWS EC2 using Route53. Point out several important issues.

  • Ecobee3 installation with K wire

    Posted on: Fri, 12/01/2017 - 06:13 By: Huahai

    How to install Ecobee3 smart thermostat when one of the existing wire connection is labeled K on the old device? This is problematic because K wire does not appear in the Ecobee3's documentation, nor in the on screen menu. I found a solution: simply connect the K wire to Y1, then enable the G connection on Ecobee3 configuration screen.​

  • Data-Oriented Programming (DOP)

    Posted on: Sat, 12/03/2016 - 23:33 By: Huahai

    JSON is arguably the world's most popular human readable data format today.  It has largely replaced XML as the data exchange format on the Internet. One of the key reasons for the proliferation of JSON is its simplicity.  The data structure are very limited: only arrays, enclosed with []; and objects, enclosed with {}. That's it. It cannot be simpler.

    Apparently, this dead simple data format is enough to represent the vast landscape of data that JSON becomes the de-facto data format for Web services. Most Web APIs we use today speaks JSON. However, JSON is not native for most programming languages. It becomes a pain to convert to and back from JSON in programming languages.

  • 从变量说开来

    Posted on: Wed, 02/25/2015 - 22:07 By: Huahai

    数学的变量与计算机语言的变量不同。数学的变量更抽象,是真的变量。而计算机语言
    的变量是假的,其实还是属性,是某个内存地址或者寄存器的属性。

    一个非程序员A,第一次编程,看到变量,会很疑惑,比如我当年,“这是什么东西的
    的变量啊”, variable for what? 后来明白了,原来就是一个地址可以存不同的东西啊
    ,明白了。指针?这不是很明显么,就是地址啊,有什么难的?

    另一个非程序员B,第一次编程,看到变量,说,哦,我知道,数学上小学就学了的,
    变量就是数学上的变量啊,懂了。结果看到指针,panic了,数学上没有指针啊,
    到底什么是指针啊?

    人和人的思维方式不一样,从对数学的态度可以看出。有的人,比如冯诺伊曼,说“
    You don't need to *understand* mathematics, you just get used to it". 这种人
    就是上面的非程序员B。这些人成为数学家的话,一般会成为分析学家。中国培养出的
    职业数学家,大多是分析学家,比如张益唐之类,解决问题能力很强,一般不自己发明
    理论。

    另外一些人,比如Grothendieck,一定要把数学理解成某种结构才行,这种人成为数学
    家的话,会成为几何或者代数学家。这些人解决问题的能力不一定强,比如
    Grothendieck连57不是prime都不知道,但他发明了改变数学界的理论。这些人也是非
    程序员A。

    上述两种人可以用一个简单的测试来区分:给他一个玉米棒子,看他怎么啃。分析学家
    会啃得乱七八糟的,代数家会啃得一排排整整齐齐的。我有时在聚会时让大家做这个游
    戏,目前发现,中国人还是分析家居多。

  • How to get a kitty manicure

    Posted on: Wed, 09/04/2013 - 06:34 By: Huahai

    Speaker: Tom

    Dear fellow kitties, I am going to show you how to get a kitty manicure and pedicure.

    First of all, let me show you my beautiful finger nails. My mom polishes each and every one of them on a weekly basis. Such weekly pampering is essential for a purrfect kitty like me.

    Now, let me show you how to get a kitty manicure.

    First of all, relax and get each of your finger massaged. I like to sit on my mommy's lap to do the massage, but Mayori prefers to get her massage in her favorite bed.

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