Implicit classes in Scala do not have to extend AnyVal

Implicit classes in Scala do not have to extend AnyVal

What are implicit classes?

Implicit classes are a feature that allow you to extend the functionality of existing types by adding new methods. They are defined using the implicit keyword and have a single constructor parameter. We can use these class as if they belong to the original type without having to perform explicit type conversion.

Implicit classes are particularly useful for adding utility methods to existing types. They allow you to do this without creating a new type or modifying the original type. You can also use implicit classes to add implicit conversions. It can be helpful in making your code more concise and readable.

Should implicit classes always extend AnyVal in scala?

Implicit classes in Scala do not have to extend AnyVal. They can extend any type that is a subtype of Any. However, if the implicit class is meant to be used as a value type and is simple enough, it may make sense to extend AnyVal to allow for optimized storage and improved performance.

It’s worth noting that an implicit class that extends AnyVal can only have a single constructor parameter and is subject to certain restrictions in terms of its functionality, as it is meant to represent a value type. On the other hand, implicit classes that do not extend AnyVal are treated as normal classes and can have multiple constructor parameters, additional fields, and more complex logic.

So whether or not an implicit class should extend AnyVal depends on the specific use case and the intended behavior of the class.

Examples:

Here’s an example to illustrate the difference between implicit classes that extend AnyVal and those that do not.

Let’s say we want to add a method to the Int type that squares its value. We can define an implicit class that takes an Int value and adds this method:

implicit class IntOps(val x: Int) extends AnyVal {

  def square: Int = x * x

}

In this case, the implicit class extends AnyVal, so it is optimized for use as a value type. We can use this implicit class like this:

scala> 5.square

res0: Int = 25

Now, let’s say we want to add a similar method to the String type that repeats its value a specified number of times. To do this, we can define an implicit class that takes a String value and adds this method:

implicit class StringOps(val s: String) {

  def repeat(n: Int): String = s * n

}

In this case, the implicit class does not extend AnyVal, because it is not meant to be used as a value type. We can treat it as a normal class. We can use this implicit class like this:

scala> "Hello ".repeat(3)

res1: String = Hello Hello Hello 

So, in this example, the implicit class that extends AnyVal is more optimized for performance as a value type, while the implicit class that does not extend AnyVal is treated as a normal class and can handle more complex logic.

Here’s one more example. Let’s say we want to add a method to the Int type that calculates the factorial of a number. We can define an implicit class that takes an Int value and adds this method:

implicit class IntFactorial(val n: Int) {

  def factorial: Int = {

    def fact(x: Int, acc: Int): Int =

      if (x <= 1) acc else fact(x - 1, acc * x)

    fact(n, 1)

  }

}

In this case, the implicit class does not extend AnyVal, because it needs to perform a recursive calculation, which is not possible with value types. We can use this implicit class like this:

cala> 5.factorial

res2: Int = 120

So, in this example, we see that extending AnyVal is not always the right choice, as the more complex logic required by the factorial method makes it more appropriate to use a normal class that does not extend AnyVal.

Conclusion:

In conclusion, whether or not an implicit class in Scala should extend AnyVal depends on the intended use case and behavior of the class. If the implicit class is meant to be used as a simple value type, then extending AnyVal can result in improved performance and optimized storage. On the other hand, if the implicit class requires more complex logic or additional fields, it may make more sense to treat it as a normal class and not extend AnyVal. In either case, implicit classes can be a convenient way to add new methods to existing types in Scala, and the choice of whether to extend AnyVal or not should be based on the specific requirements of each case.

Original article source at: https://blog.knoldus.com/

#scala #classes 

What is GEEK

Buddha Community

Superdom: Better and Simpler ES6 DOM Manipulation

Superdom

You have dom. It has all the DOM virtually within it. Use that power:

// Fetch all the page links
let links = dom.a.href;

// Links open in a new tab
dom.a.target = '_blank';

Only for modern browsers

Getting started

Simply use the CDN via unpkg.com:

<script src="https://unpkg.com/superdom@1"></script>

Or use npm or bower:

npm|bower install superdom --save

Select

It always returns an array with the matched elements. Get all the elements that match the selector:

// Simple element selector into an array
let allLinks = dom.a;

// Loop straight on the selection
dom.a.forEach(link => { ... });

// Combined selector
let importantLinks = dom['a.important'];

There are also some predetermined elements, such as id, class and attr:

// Select HTML Elements by id:
let main = dom.id.main;

// by class:
let buttons = dom.class.button;

// or by attribute:
let targeted = dom.attr.target;
let targeted = dom.attr['target="_blank"'];

Generate

Use it as a function or a tagged template literal to generate DOM fragments:

// Not a typo; tagged template literals
let link = dom`<a href="https://google.com/">Google</a>`;

// It is the same as
let link = dom('<a href="https://google.com/">Google</a>');

Delete elements

Delete a piece of the DOM

// Delete all of the elements with the class .google
delete dom.class.google;   // Is this an ad-block rule?

Attributes

You can easily manipulate attributes right from the dom node. There are some aliases that share the syntax of the attributes such as html and text (aliases for innerHTML and textContent). There are others that travel through the dom such as parent (alias for parentNode) and children. Finally, class behaves differently as explained below.

Get attributes

The fetching will always return an array with the element for each of the matched nodes (or undefined if not there):

// Retrieve all the urls from the page
let urls = dom.a.href;     // #attr-list
  // ['https://google.com', 'https://facebook.com/', ...]

// Get an array of the h2 contents (alias of innerHTML)
let h2s = dom.h2.html;     // #attr-alias
  // ['Level 2 header', 'Another level 2 header', ...]

// Get whether any of the attributes has the value "_blank"
let hasBlank = dom.class.cta.target._blank;    // #attr-value
  // true/false

You also use these:

• html (alias of innerHTML): retrieve a list of the htmls
• text (alias of textContent): retrieve a list of the htmls
• parent (alias of parentNode): travel up one level
• children: travel down one level

Set attributes

// Set target="_blank" to all links
dom.a.target = '_blank';     // #attr-set

dom.class.tableofcontents.html = `
  <ul class="tableofcontents">
    ${dom.h2.map(h2 => `
      <li>
        <a href="#${h2.id}">
          ${h2.innerHTML}
        </a>
      </li>
    `).join('')}
  </ul>
`;

Remove an attribute

To delete an attribute use the delete keyword:

// Remove all urls from the page
delete dom.a.href;

// Remove all ids
delete dom.a.id;

Classes

It provides an easy way to manipulate the classes.

Get classes

To retrieve whether a particular class is present or not:

// Get an array with true/false for a single class
let isTest = dom.a.class.test;     // #class-one

For a general method to retrieve all classes you can do:

// Get a list of the classes of each matched element
let arrays = dom.a.class;     // #class-arrays
  // [['important'], ['button', 'cta'], ...]

// If you want a plain list with all of the classes:
let flatten = dom.a.class._flat;     // #class-flat
  // ['important', 'button', 'cta', ...]

// And if you just want an string with space-separated classes:
let text = dom.a.class._text;     // #class-text
  // 'important button cta ...'

Add a class

// Add the class 'test' (different ways)
dom.a.class.test = true;    // #class-make-true
dom.a.class = 'test';       // #class-push

Remove a class

// Remove the class 'test'
dom.a.class.test = false;    // #class-make-false

Manipulate

Did we say it returns a simple array?

dom.a.forEach(link => link.innerHTML = 'I am a link');

But what an interesting array it is; indeed we are also proxy'ing it so you can manipulate its sub-elements straight from the selector:

// Replace all of the link's html with 'I am a link'
dom.a.html = 'I am a link';

Of course we might want to manipulate them dynamically depending on the current value. Just pass it a function:

// Append ' ^_^' to all of the links in the page
dom.a.html = html => html + ' ^_^';

// Same as this:
dom.a.forEach(link => link.innerHTML = link.innerHTML + ' ^_^');

Note: this won't work dom.a.html += ' ^_^'; for more than 1 match (for reasons)

Or get into genetics to manipulate the attributes:

dom.a.attr.target = '_blank';

// Only to external sites:
let isOwnPage = el => /^https?\:\/\/mypage\.com/.test(el.getAttribute('href'));
dom.a.attr.target = (prev, i, element) => isOwnPage(element) ? '' : '_blank';

Events

You can also handle and trigger events:

// Handle click events for all <a>
dom.a.on.click = e => ...;

// Trigger click event for all <a>
dom.a.trigger.click;

Testing

We are using Jest as a Grunt task for testing. Install Jest and run in the terminal:

grunt watch

Download Details:

Author: franciscop
Source Code: https://github.com/franciscop/superdom 
License: MIT license

#javascript #es6 #dom 

Implicit classes in Scala do not have to extend AnyVal

Implicit classes in Scala do not have to extend AnyVal

What are implicit classes?

Implicit classes are a feature that allow you to extend the functionality of existing types by adding new methods. They are defined using the implicit keyword and have a single constructor parameter. We can use these class as if they belong to the original type without having to perform explicit type conversion.

Implicit classes are particularly useful for adding utility methods to existing types. They allow you to do this without creating a new type or modifying the original type. You can also use implicit classes to add implicit conversions. It can be helpful in making your code more concise and readable.

Should implicit classes always extend AnyVal in scala?

Implicit classes in Scala do not have to extend AnyVal. They can extend any type that is a subtype of Any. However, if the implicit class is meant to be used as a value type and is simple enough, it may make sense to extend AnyVal to allow for optimized storage and improved performance.

It’s worth noting that an implicit class that extends AnyVal can only have a single constructor parameter and is subject to certain restrictions in terms of its functionality, as it is meant to represent a value type. On the other hand, implicit classes that do not extend AnyVal are treated as normal classes and can have multiple constructor parameters, additional fields, and more complex logic.

So whether or not an implicit class should extend AnyVal depends on the specific use case and the intended behavior of the class.

Examples:

Here’s an example to illustrate the difference between implicit classes that extend AnyVal and those that do not.

Let’s say we want to add a method to the Int type that squares its value. We can define an implicit class that takes an Int value and adds this method:

implicit class IntOps(val x: Int) extends AnyVal {

  def square: Int = x * x

}

In this case, the implicit class extends AnyVal, so it is optimized for use as a value type. We can use this implicit class like this:

scala> 5.square

res0: Int = 25

Now, let’s say we want to add a similar method to the String type that repeats its value a specified number of times. To do this, we can define an implicit class that takes a String value and adds this method:

implicit class StringOps(val s: String) {

  def repeat(n: Int): String = s * n

}

In this case, the implicit class does not extend AnyVal, because it is not meant to be used as a value type. We can treat it as a normal class. We can use this implicit class like this:

scala> "Hello ".repeat(3)

res1: String = Hello Hello Hello 

So, in this example, the implicit class that extends AnyVal is more optimized for performance as a value type, while the implicit class that does not extend AnyVal is treated as a normal class and can handle more complex logic.

Here’s one more example. Let’s say we want to add a method to the Int type that calculates the factorial of a number. We can define an implicit class that takes an Int value and adds this method:

implicit class IntFactorial(val n: Int) {

  def factorial: Int = {

    def fact(x: Int, acc: Int): Int =

      if (x <= 1) acc else fact(x - 1, acc * x)

    fact(n, 1)

  }

}

In this case, the implicit class does not extend AnyVal, because it needs to perform a recursive calculation, which is not possible with value types. We can use this implicit class like this:

cala> 5.factorial

res2: Int = 120

So, in this example, we see that extending AnyVal is not always the right choice, as the more complex logic required by the factorial method makes it more appropriate to use a normal class that does not extend AnyVal.

Conclusion:

In conclusion, whether or not an implicit class in Scala should extend AnyVal depends on the intended use case and behavior of the class. If the implicit class is meant to be used as a simple value type, then extending AnyVal can result in improved performance and optimized storage. On the other hand, if the implicit class requires more complex logic or additional fields, it may make more sense to treat it as a normal class and not extend AnyVal. In either case, implicit classes can be a convenient way to add new methods to existing types in Scala, and the choice of whether to extend AnyVal or not should be based on the specific requirements of each case.

Original article source at: https://blog.knoldus.com/

#scala #classes 

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Let's Talk About Implicit

I hope from the above picture you can get an idea of “how an implicit can be useful”. This is just a single use case and if you are more interested in knowing about Implicit then this blog is for you. In this blog, I am going to discuss Implicit in Scala. I hope this will be useful to you. So, let’s talk about implicit

What Is Implicit?

The literal meaning of implicit is “Something that is suggested or implied”. We can see it as something that is not directly or that someone understands themselves. In Scala also, the implicit has pretty much similar meaning. Before going into much detail, I’ll take a simple example and explain how the compiler implements it.

#java #tutorial #scala #implicit #implicits #implicit conversions

Should Implicit Classes Always Extend AnyVal?

What are implicit classes?

Implicit classes are a feature that allow you to extend the functionality of existing types by adding new methods. They are defined using the implicit keyword and have a single constructor parameter. We can use these class as if they belong to the original type without having to perform explicit type conversion.

Implicit classes are particularly useful for adding utility methods to existing types. They allow you to do this without creating a new type or modifying the original type. You can also use implicit classes to add implicit conversions. It can be helpful in making your code more concise and readable.

Should implicit classes always extend AnyVal in scala?

Implicit classes in Scala do not have to extend AnyVal. They can extend any type that is a subtype of Any. However, if the implicit class is meant to be used as a value type and is simple enough, it may make sense to extend AnyVal to allow for optimized storage and improved performance.

It’s worth noting that an implicit class that extends AnyVal can only have a single constructor parameter and is subject to certain restrictions in terms of its functionality, as it is meant to represent a value type. On the other hand, implicit classes that do not extend AnyVal are treated as normal classes and can have multiple constructor parameters, additional fields, and more complex logic.

So whether or not an implicit class should extend AnyVal depends on the specific use case and the intended behavior of the class.

Examples:

Here’s an example to illustrate the difference between implicit classes that extend AnyVal and those that do not.

Let’s say we want to add a method to the Int type that squares its value. We can define an implicit class that takes an Int value and adds this method:

implicit class IntOps(val x: Int) extends AnyVal {

  def square: Int = x * x

}

In this case, the implicit class extends AnyVal, so it is optimized for use as a value type. We can use this implicit class like this:

scala> 5.square

res0: Int = 25

Now, let’s say we want to add a similar method to the String type that repeats its value a specified number of times. To do this, we can define an implicit class that takes a String value and adds this method:

implicit class StringOps(val s: String) {

  def repeat(n: Int): String = s * n

}

In this case, the implicit class does not extend AnyVal, because it is not meant to be used as a value type. We can treat it as a normal class. We can use this implicit class like this:

scala> "Hello ".repeat(3)

res1: String = Hello Hello Hello 

So, in this example, the implicit class that extends AnyVal is more optimized for performance as a value type, while the implicit class that does not extend AnyVal is treated as a normal class and can handle more complex logic.

Here’s one more example. Let’s say we want to add a method to the Int type that calculates the factorial of a number. We can define an implicit class that takes an Int value and adds this method:

implicit class IntFactorial(val n: Int) {

  def factorial: Int = {

    def fact(x: Int, acc: Int): Int =

      if (x <= 1) acc else fact(x - 1, acc * x)

    fact(n, 1)

  }

}

In this case, the implicit class does not extend AnyVal, because it needs to perform a recursive calculation, which is not possible with value types. We can use this implicit class like this:

scala> 5.factorial

res2: Int = 120

So, in this example, we see that extending AnyVal is not always the right choice, as the more complex logic required by the factorial method makes it more appropriate to use a normal class that does not extend AnyVal.

Conclusion:

In conclusion, whether or not an implicit class in Scala should extend AnyVal depends on the intended use case and behavior of the class. If the implicit class is meant to be used as a simple value type, then extending AnyVal can result in improved performance and optimized storage. On the other hand, if the implicit class requires more complex logic or additional fields, it may make more sense to treat it as a normal class and not extend AnyVal. In either case, implicit classes can be a convenient way to add new methods to existing types in Scala, and the choice of whether to extend AnyVal or not should be based on the specific requirements of each case.

Original article source at: https://blog.knoldus.com/

#classes #scala