Wayne Chu

Redefine comparator in Python and Ruby

## Python In python, there are several magic functions for comparing: * `__eq__(self, other)` 定義了等號的行為` ==` 。 * `__ne__(self, other)` ...

Rails 6 ActiveStorage updates

工作上有用到 ActiveStorage，然後我又手癢想升級 Rails，所以先記錄一下 https://blog.saeloun.com/2019/11/04/rails-6-active-storage-updates.html

How Ruby REALLY uses Memory: On the Web and Beyond

好文，強烈建議閱讀全文 => https://www.schneems.com/2019/11/06/how-ruby-really-uses-memory-on-the-web-and-beyond/ ## TL;DR: - Tread 越多 memory usag...

Ruby yield_self and then syntax

## TL;DR: 1. `yield_self` == `then` 2. `yield_self` returns the result of the block ## yield_self Introduced in Ruby v2.5 Difference...

Ruby multiline string

## With indention version ```rb indented = <<-EOS Hello This is an example. I have to write this multiline string outside the we...

uniq list in Python

```py list(set([1,2,2,3])) # => [1,2,3] ``` functional style

How to sort a list in Python

## 1. Object oriented way: ```python list = [4,3,2,1] list.sort() # => return nothing list # => [1,2,3,4] ``` - called from object ...

Finally we have multi env credential in Rails 6

In Rails 6, default credential is for development and staging, they'll store in the same path ``` config/credentials.yml.enc config/mast...

When to use Hash and when to use HashWithIndifferentAccess and why

## TL;DR: * When passing to our class: Both works, because we control everything * When passing to 3rd party library: Hash is better, we...

Keyword argument in Ruby 3

https://blog.saeloun.com/2019/10/07/ruby-2-7-keyword-arguments-redesign.html

Can't find custom headers in Axios response

It's CORS issue, configure CORS setting for browser will fix this. https://stackoverflow.com/questions/37897523/axios-get-access-to-resp...

給高中沒學好或是已經忘記的同學的 CS 基礎知識 cheatsheet

https://youtu.be/TOsMcgIK95k

複習一下各種排序法，和 Python 實現

搭配題目和講解影片服用： * Lintcode: https://www.lintcode.com/problem/sort-integers * Leetcode: https://leetcode.com/problems/sort-an-array/ * https...

Remove Duplicate Numbers in Array

## Question https://www.lintcode.com/problem/remove-duplicate-numbers-in-array/description https://leetcode.com/problems/remove-duplicat...

Classical Binary Search - recursion version

## Question: 457. Classical Binary Search Find any position of a target number in a sorted array. Return -1 if target does not exist. ...

什么是拓扑排序（Topological Sorting）

直接 copy 過來： 一、什么是拓扑排序 在图论中，拓扑排序（Topological Sorting）是一个有向无环图（DAG, Directed Acyclic Graph）的所有顶点的线性序列。且该序列必须满足下面两个条件： 每个顶点出现且只出现一次。 若存在一...

rspec 3 composable matchers

http://rspec.info/blog/2014/01/new-in-rspec-3-composable-matchers/

Python deque 用法

1. deque 類似於 list (ruby 的 array)，只不過 deque 可以操作兩端 2. deque 是 tread safe，所以可以同時操作 何謂操作兩端？這個 example 看一下即了解： ```py import collections d1...

Graph theory basic - Set and adjacency list

![Graph Example](https://waynechu.cc/rails/active_storage/blobs/eyJfcmFpbHMiOnsibWVzc2FnZSI6IkJBaHBCZz09IiwiZXhwIjpudWxsLCJwdXIiOiJibG9iX...

4 basic proof technique in math

## Some basic P => Q P: If statement Q: Tehn statement example: `If a < b, then a < b + 1`，`If a < b` 是 P, `then a < b+1` 是 Q ## 1....

Some Python tools

List few tools that I find helpful for Python's beginner learner - Console: https://ipython.org/ - IDE: https://www.jetbrains.com/pycha...

Writing idiomatic python 3

Recomended http://downloads.niceware.com/TECH-pdf/PythonStyle-Writing_idiomatic_python_3.pdf?fbclid=IwAR1uhD-_8WRmWy1Sb2Ncz9Afwk248-o5JA...

Time complexity and space complexity

時間複雜度跟空間複雜度 ## 時間複雜度 常見的六種時間複雜度與演算法 * O(1)：陣列讀取 * O(n)：簡易搜尋 * O(log n)：二分搜尋 * O(nlogn)：合併排序 * O(n²)：選擇排序 * O(2^n)：費波那契數列 時間複雜度為 O(n) ...

Start using Stripe's PaymentIntent instead of Charge to fit SCA

Since a new rule coming into effect on September 14, 2019, as part of PSD2 regulation in Europe, any integrations using the Charges API w...

Rails 6 released

https://weblog.rubyonrails.org/2019/8/15/Rails-6-0-final-release/