### Java 8 - Using Functions as Values

The following is a series of posts about "functional programming in Java" which is the result of my understanding by reading the book "Java 8 in Action: Lambdas, Streams, and Functional-style Programming, by Alan Mycroft and Mario Fusco".
1. Why functional programming?
2. Functional programming in Java 8
3. Java 8 - Using Functions as Values
4. Java 8 - Persistent data structure

In general, the phrase "functional-style programming" means the behavior of functions should be like that of mathematical-style functions - no side effects.

In programmers' point of views, functions may be used like other values: passed as arguments, returned as result, and stored in data structures. That means we can use the :: operator to create a method reference, and lambda expressions to directly express function values. For example:
//method reference
Function<String, Integer> strToInt = Integer::parseInt;

//lambda expression
Comparator<Integer> comparator = (a, b) -> a.compareTo(b);

There are two practical techniques to apply in our codebase.

## Higher-order functions

For example:
 Comparator<Apple> c = Comparator.comparing(Apple::getWeight);

Higher-order functions (like Comparator.comparing) that can do at least one of following:
• Take one or more functions as parameter
• Return a function as result
Foo: If so, for what?
Bar: Good question! To compose functions to create a pipeline of operations. It's close to declarative programming.

## Currying

A function of two arguments (x and y, say) is seen instead as a function g of one argument that returns a function also one argument. The value returned by the latter function is the same as the value of the original function, that is, f(x,y) = (g(x))(y).

Brain overload! For example, you want to convert Celsius to Fahrenheit, the formula is f(x) = x *9/5 + 32. Not only this case but we can see the basic pattern of all unit conversion is as follow:
static double converter(double x, double f, double b) {
return x * f + b;
}

This method is a bit too general. Obviously, we can use it to apply for all unit conversion but it would be tedious and you might accidentally mistyped them. There is an better approach:
static DoubleUnaryOperator curriedConverter(double f, double b){
return (double x) -> x * f + b;
}

Instead of passing all the arguments x, f and b all at once to the converter method, you only ask for the arguments f and b and return another function, which given an argument x return x*f + b.

Why is it the better approach? This enables you to reuse the convention logic and create different functions with different convention factors:
DoubleUnaryOperator convertCtoF = curriedConverter(9.0/5, 32);
DoubleUnaryOperator convertUSDtoGBP = curriedConverter(0.6, 0);
DoubleUnaryOperator convertKmtoMi = curriedConverter(0.6214, 0);
Instead of three different method for each conversion factor:
static double convertCtoF(double x, double f, double b) {
return x * f + b;
}

static double convertUSDtoGBP(double x, double f, double b) {
return x * f + b;
}

static double convertUSDtoGBP(double x, double f, double b) {
return x * f + b;
}

Foo: If so, for what?
Bar: It helps you modularize functions and reuse code!

Reference

[1]. Alan Mycroft and Mario Fusco, Java 8 in Action: Lambdas, Streams, and Functional-style Programming. Part 4. Beyond Java 8.

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### AngularJS - Build a custom validation directive for using multiple emails in textarea

AngularJS already supports the built-in validation with text input with type email. Something simple likes the following:
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Note that, there is the $asyncValidators object which handles asynchronous validation, such as making an$http request to the backend.

This is just my implementation on my project. In order to understand that, I supposed you already had experiences with Angular…

### Creating a Chatbot with RiveScript in Java

Motivation"Artificial Intelligence (AI) is considered a major innovation that could disrupt many things. Some people even compare it to the Internet. A large investor firm predicted that some AI startups could become the next Apple, Google or Amazon within five years"
- Prof. John Vu, Carnegie Mellon University.

Using chatbots to support our daily tasks is super useful and interesting. In fact, "Jenkins CI, Jira Cloud, and Bitbucket" have been becoming must-have apps in Slack of my team these days.

There are some existing approaches for chatbots including pattern matching, algorithms, and neutral networks. RiveScript is a scripting language using "pattern matching" as a simple and powerful approach for building up a Chabot.
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Used Technologies and ToolsOracle JDK 1.8.0_151Apache Maven 3.5…

### Styling Sort Icons Using Font Awesome for Primefaces' Data Table

So far, Primefaces has used image sprites for displaying the sort icons. This leads to a problem if we want to make a different style for these icons; for example, I would make the icon "arrow up" more blurry at the first time the table loading because I want to highlight the icon "arrow down". I found a way that I can replace these icons with Font Awesome icons.

We will use "CSS Pseudo-classes" to achieve it. The hardest thing here is that we should handle displaying icons in different cases. There is a case both "arrow up" and "arrow down" showing and other case is only one of these icons is shown.

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Mathematicians like to classify the d

### Applying pipeline “tensorflow_embedding” of Rasa NLU

According to this nice article, there was a new pipeline released using a different approach from the standard one (spacy_sklearn). I wanted to give it a try to see whether it can help with improving bot’s accuracy.

After applying done, I gave an evaluation of “tensorflow_embedding”. It seemed to work better a bit. For example, I defined intents “greet” and “goodbye” with some following messages in my training data.
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