If you are already using bcoin as part of your bitcoin infrastructure and need to sign transactions on a Ledger, you have come to the right place.

We’ve found that Bledger, which is found in bcoin’s open source library, works well to connect to the ledger hardware wallet.

Linked List

As of writing this, this is currently implemented in Swift 1.0. May not work on Swift 2.0+ .

In computer science, a linked list is a data structure consisting of a group of nodes which together represent a sequence. It is a way to associate related content. There are two major operations for linked list; insert and remove. We will go over both of these operations and it’s implementation in Swift.


Each node has a value(data) and a reference to the next node. The reference is typically a pointer or a memory address where the next value can be found…

A stack is an abstract data type or collection that helps organizes data in a particular order. This concept is based on the idea that information can be organized in a similar way on things work in the real world. The operations for adding an entity to the stack is known as push and the removal known as pop.


Think of a stack of dishes. The first dish placed on the table, while the next dish is placed on top of the first dish. Then the 3rd dish is placed on the 2nd dish, and so on and so forth…

As someone coming from a web development background, learning iOS development can a bit challenging. One concept I’ve seen those who are new to iOS get confused with is the difference between UIImage, CIImage, and CGImage.

From a high level view, there is a difference because all of UIKit, CoreImage, and CoreGraphics does fundamentally different things that there can not be a unified image format. These frameworks, however, work together well. The conversion are optimized and as fast as possible.


Apple describes a UIImage object as a high-level way to display image data. You can create images from files, from…


An optional in Swift is basically a constant or variable that can hold a value OR no value. The value can or cannot be nil. It is denoted by appending a “?” after the type declaration. For example:

var tweet: String?

The tweet string is now declared as an optional.

This is a big impact on the language Swift itself because what that means is that anything non-optional types can never be nil. As someone coming from a different language like Javascript and Ruby, this was a weird concept to grasp. However, it is actually very powerful when used. …

Let’s learn together

Randall Leung

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