# Draft

## Table of Contents

## 1 Remarkable

## 2 Android

H2O APN setting

- Name: ATT Nextgenphone
- APN: att.mvno
- Port: 80
- MMSC: http://mmsc.mobile.att.net
- MMS Proxy: 66.209.11.33
- MMS Port: 80
- MCC: 310
- MNC: 410
- APN Type: default, mms, supl, fota, hipri
- APN Protocol: IPv4/IPv6

Unset but with value:

- MVNO Type: None
- Bearer: Unspecified

Everything else Not set, including

- Proxy
- Username
- Password
- Server
- Authentication Type
- MVNO Value

## 3 C

### 3.1 Context Sensitivity of C

- https://eli.thegreenplace.net/2007/11/24/the-context-sensitivity-of-cs-grammar/
- The lexer hack https://en.wikipedia.org/wiki/The_lexer_hack
- Clang use a thin lexer to avoid this problem, which is what I'm going to use as well

Here is the C lexer rule and grammar for yacc

## 4 Math

### 4.1 Calculus

Calculus has two main branches:

- differential calculus
- it is mainly about derivative. The process of finding a derivative is called differentiation.
- \(\frac{dy}{dx}|_{a}\) is Leibniz's notation
- f'(a) is Lagrange's notation

- integral calculus
- definite integral
- indefinite integral (also antiderivative)

### 4.2 Lagrange multiplier

When solving a maxima of a function, with subject to a constraint, we
often use *Lagrange multiplier*. Say:

- maximize \(f(x,y)\)
- subject to \(g(x,y)=0\)

We are going to introduce the Lagrange multiplier \(\lambda\) such that

- \(L(x,y,\lambda) = f(x,y) - \lambda g(x,y)\) is called Lagrange function.
- Compute the gradient of L, and compute the stationary points. Those points will be the space of the solution to the original maxima problem.

The intuition: at a maximum, f(x,y) cannot be increasing in the direction of any neighboring point where g = 0.