Rakhmad Azhari rakhmad

System Design Cheatsheet

Picking the right architecture = Picking the right battles + Managing trade-offs

Basic Steps

Clarify and agree on the scope of the system

User cases (description of sequences of events that, taken together, lead to a system doing something useful)
- Who is going to use it?
- How are they going to use it?

Simple Security Guidelines

Using an iDevice? (Best option)

Use an iPod or an iPad without a SIM card
Use an iPhone
Do not jailbreak
Always upgrade to new iOS versions
Use Brave browser

Need Secure chat?

📂 Persistent "pipes" in Linux

In a project I'm working on I ran into the requirement of having some sort of persistent FIFO buffer or pipe in Linux, i.e. something file-like that could accept writes from a process and persist it to disk until a second process reads (and acknowledges) it. The persistence should be both across process restarts as well as OS restarts.

AFAICT unfortunately in the Linux world such a primitive does not exist (named pipes/FIFOs do not persist

A monad is a fancy word for a generic type of the form MyMonad<T> (a generic type of arity 1).

A monad is special because it adds 'special powers' to the T that it wraps. These 'special powers' won't sound very special to an imperative programmer, so you have to squint to see them but bear with me.

IEnumerable<T> is a monad that gives values of type T the special power of nondeterminism, or the ability to 'be' multiple values at once.
Nullable<T> is a monad that gives values of type T the special power of nullability, or the ability to be absent.
Task<T> is a monad that gives values of type T the special power of asynchronicity, or the ability to be used before they are computed.

The trick with monads comes when you want to play with the T values, because they are inside another type. C# introduced language changes to make dealing with values inside these monads easier:

Here's my own list of the interesting stuff announced during this year's WWDC, collected from the keynotes, various Apple docs, blog posts and tweets.

If you're planning to watch the videos, I really recommend this Mac app that helps you download and watch them: https://github.com/insidegui/WWDC.

OS X El Capitan

http://www.apple.com/osx/elcapitan-preview/

split view - two apps side by side on full screen

Introduction to scalaz-stream

Every application ever written can be viewed as some sort of transformation on data. Data can come from different sources, such as a network or a file or user input or the Large Hadron Collider. It can come from many sources all at once to be merged and aggregated in interesting ways, and it can be produced into many different output sinks, such as a network or files or graphical user interfaces. You might produce your output all at once, as a big data dump at the end of the world (right before your program shuts down), or you might produce it more incrementally. Every application fits into this model.

The scalaz-stream project is an attempt to make it easy to construct, test and scale programs that fit within this model (which is to say, everything). It does this by providing an abstraction around a "stream" of data, which is really just this notion of some number of data being sequentially pulled out of some unspecified data source. On top of this abstraction, sca

CSS Layout Debugger

A tweet-sized debugger for visualizing your CSS layouts. Outlines every DOM element on your page a random (valid) CSS hex color.

One-line version to paste in your DevTools

Use $$ if your browser aliases it:

~ 108 byte version

	/// Observes a run loop to detect any stalling or blocking that occurs.
	///
	/// This class is thread-safe.
	@interface GHRunLoopWatchdog : NSObject

	/// Initializes the receiver to watch the specified run loop, using a default
	/// stalling threshold.
	- (id)initWithRunLoop:(CFRunLoopRef)runLoop;

	/// Initializes the receiver to detect when the specified run loop blocks for

	@interface UIWindow (resize)
	-(void)_adjustSizeClassesAndResizeWindowToFrame:(CGRect)frame;
	@end

	typedef enum _UICustomRes
	{
	UICustomResiPadTwoThirds,
	UICustomResiPadHalf,
	UICustomResiPadOneThird,
	UICustomResiPhone47,