## Pokémon Let's Go Pikachu 一周目通关

我感恩节期间买了 Nintendo Switch，是为了玩 Pokémon Let's Go Pikachu，也就是《口袋妖怪·黄》的重制版，为此我还配上了 Pokéball Plus（配信梦幻的精灵球形状的遥控器，也可以作计步器用）。刚刚结束一周目（登入名人堂），写篇博文记录一下。

我感恩节期间买了 Nintendo Switch，是为了玩 Pokémon Let's Go Pikachu，也就是《口袋妖怪·黄》的重制版，为此我还配上了 Pokéball Plus（配信梦幻的精灵球形状的遥控器，也可以作计步器用）。刚刚结束一周目（登入名人堂），写篇博文记录一下。

我的博客中第一次提到《铁甲小宝》是在《清华网络碎碎念：交费死锁》，最近我又在杂乱地复习它，发现了一些有趣的事情。本篇博文介绍这些内容，并记录一些备忘知识。

Sharing data among apps is a common task in modern operating system. Both iOS and Windows Runtime provides central means of transmitting data from one app to another beyond the clipboard. In this entry, I will look at the sharing functionalities in both systems.

这次 Microsoft 和 Apple 都令人恼火！

Group presentation is a method to express groups as a quotient of a free group and a normal subgroup. In a presentation, there are generators and relators, and the presentation yields a ‘minimalist implementation’ of these generators and relations. Some cases of special interests are finitely generated/related/presented groups. From the definition, finite generation + finite relation is not linguistically equivalent to finite presentation. There has been some discussion on the relation of the three properties for several other algebraic structures. This entry proves that finite generation + finite relation imples finite presentation for groups.

理想（ideal）是出现在抽象代数（更特别地，环论）中的一类对象，其命名很有渊源。之前我只知道这个名字来源于一位数学家研究惟一分解时引入的“理想数”（该研究的思路和一般化最终形成了现代数学语言中“理想”的定义），但是具体的细节不是很明白；最近在阅读基于格（lattice）的密码学的内容，其中提到了环上的格（ring lattice），其中提到了理想格（环的一个子集，同时满足格和理想的要求），好奇心一发不可收拾，读了一些数学历史故事，对“理想数”加深了认识，记录下来以飨观众。文章最后讨论了“理想数”这个翻译的不达意之处。

A brain teaser that remains open in Yao class WeChat group, up to the time of writing of this entry. See if it interests you and if you can solve it.

A meta-blog that keeps the trace of my blog site. You will find the font size of this website less intimidating now. Plus, Google Plus share button has been removed.

I’m taking an algebra course and regaining my algebra sense (non-sense?). Familiar to us is that direct products [resp. sums] of groups [resp. abelian groups] possess their versions of universal properties. When reviewing these things, I went curious on what would go wrong if the arrows were reversed. Let’s try and see.

Issue #6799 in PowerShell repository on GitHub raises the question why Previous Versions is opening previous versions of a directory in PowerShell, instead of File Explorer as expected. The reason is that PowerShell 6.1.0 (preview) installer creates a context menu to open the shell on any folder. However, it unfortunately names the verbs as open/runas, which is very dangerous since they are canonical and do not make much sense for a folder. Related is issue #7815, where shortcuts to a folder are opened in PowerShell.