Tutorial by Examples: e

Register beans only when a property or value is specified

A spring bean can be configured such that it will register only if it has a particular value or a specified property is met. To do so, implement Condition.matches to check the property/value: public class PropertyCondition implements Condition { @Override public boolean matches(ConditionC...

spring • Conditional bean registration in Spring

Keep it simple

Do not overcomplicate simple tasks. Most of the time you will need only: algebraic datatypes structural recursion monad-like api (map, flatMap, fold) There is plenty of complicated stuff in Scala, such as: Cake pattern or Reader Monad for Dependency Injection. Passing arbitrary values as...

Scala Language • Best Practices

Don't pack too much in one expression.

Find meaningful names for computation units. Use for comprehensions or map to combine computations together. Let's say you have something like this: if (userAuthorized.nonEmtpy) { makeRequest().map { case Success(respone) => someProcessing(..) if (resendToUser) { ...

Scala Language • Best Practices

Prefer a Functional Style, Reasonably

By default: Use val, not var, wherever possible. This allows you to take seamless advantage of a number of functional utilities, including work distribution. Use recursion and comprehensionss, not loops. Use immutable collections. This is a corrolary to using val whenever possible. Focus on da...

Scala Language • Best Practices

HTML 5 Doctype

HTML5 is not based on SGML, and therefore does not require a reference to a DTD. HTML 5 Doctype declaration: <!DOCTYPE html> Case Insensitivity Per the W3.org HTML 5 DOCTYPE Spec: A DOCTYPE must consist of the following components, in this order: A string that is an ASCII case-inse...

HTML • Doctypes

Slice a file

The blob.slice() method is used to create a new Blob object containing the data in the specified range of bytes of the source Blob. This method is usable with File instances too, since File extends Blob. Here we slice a file in a specific amount of blobs. This is useful especially in cases where yo...

JavaScript • File API, Blobs and FileReaders

Working with stub entities

Say we have Products and Categorys in a many-to-many relationship: public class Product { public Product() { Categories = new HashSet<Category>(); } public int ProductId { get; set; } public string ProductName { get; set; } public virtual ICollection&lt...

Entity Framework • Optimization Techniques in EF

flatMap Operator

The flatMap operator help you to transform one event to another Observable (or transform an event to zero, one, or more events). It's a perfect operator when you want to call another method which return an Observable public Observable<String> perform(int i) { // ... } Observabl...

rx-java • Operators

NSLog and BOOL type

There is no format specifier to print boolean type using NSLog. One way to print boolean value is to convert it to a string. BOOL boolValue = YES; NSLog(@"Bool value %@", boolValue ? @"YES" : @"NO"); Output: 2016-07-30 22:53:18.269 Test[4445:64129] Bool value YES ...

Objective-C Language • Logging

Sums of Fibonacci Numbers

The Fibonacci numbers are defined inductively as F0 = 0 F1 = 1 Fn+2 = Fn + Fn+1 The sum of the first n+1 Fibonacci numbers is given by F0 + F1 + F2 + ... + Fn = Fn+2 - 1. This summation arises, among other places, in the analysis of Fibonacci heaps, where it's used to provide a lower b...

math • Common summations in computer science

Performing batch updates

You can animate complex changes to your collection view using the performBatchUpdates method. Inside the update block, you can specify several modifications to have them animate all at once. collecitonView.performBatchUpdates({ // Perform updates }, nil) Inside the update block, you can pe...

iOS • UICollectionView

Upload an image or a video to S3 using AWS SDK

Before starting with the example I'd recommend to create a Singleton with a delegate class member so you could achieve a use case of uploading a file in the background and let the user keep using your app while the files are being uploaded even when the app is the background. Let's start, first, we...

iOS • AWS SDK

Wrap simple value into a promise using $q.when()

If all you need is to wrap the value into a promise, you don't need to use the long syntax like here: //OVERLY VERBOSE var defer; defer = $q.defer(); defer.resolve(['one', 'two']); return defer.promise; In this case you can just write: //BETTER return $q.when(['one', 'two']); $q.when ...

AngularJS • Angular promises with $q service

Emacs Tutorial

C-h t runs the function help-with-tutorial, which opens a buffer containing a tutorial on the basic editing functionality of emacs, including moving around in text, and working with files, buffers, and windows.

emacs • Help Within Emacs

Available Functions and Key Bindings

Pressing C-h a will run the emacs function apropos-command which makes emacs prompt for words (or a regexp) to search for. It will then show a buffer containing a list of names and descriptions related to that topic, including key bindings for each of the functions available via keystrokes. Pressin...

emacs • Help Within Emacs

Key Binding Documentation

C-h k runs the function describe-key, which looks up the function mapped to the key strokes provided, and presents a description of the function which will be run when these keys are pressed. C-h c runs the function describe-key-briefly, which only displays the function name mapped to given key seq...

emacs • Help Within Emacs

Function Documentation

C-h f runs the function describe-function, which displays information on the usage and purpose of a given function. This is especially useful for functions that do not have a mapped key binding that can be used for documentation lookup via C-h k.

emacs • Help Within Emacs

Atomic Blocks with Software Transactional Memory

Another powerful & mature concurrency tool in Haskell is Software Transactional Memory, which allows for multiple threads to write to a single variable of type TVar a in an atomic manner. TVar a is the main type associated with the STM monad and stands for transactional variable. They're used m...

Haskell Language • Concurrency

The Data.Vector Module

The Data.Vector module provided by the vector is a high performance library for working with arrays. Once you've imported Data.Vector, it's easy to start using a Vector: Prelude> import Data.Vector Prelude Data.Vector> let a = fromList [2,3,4] Prelude Data.Vector> a fromList [2,3,4]...

Haskell Language • Vectors

Filtering a Vector

Filter odd elements: Prelude Data.Vector> Data.Vector.filter odd y fromList [1,3,5,7,9,11] :: Data.Vector.Vector

Haskell Language • Vectors