Trending February 2024 # How Xml Works In Ansible? # Suggested March 2024 # Top 9 Popular

You are reading the article How Xml Works In Ansible? updated in February 2024 on the website Kientrucdochoi.com. We hope that the information we have shared is helpful to you. If you find the content interesting and meaningful, please share it with your friends and continue to follow and support us for the latest updates. Suggested March 2024 How Xml Works In Ansible?

Definition

Ansible XML module, which is a part of the General ansible collection module and it supports the various parameters (described in the syntax section) to read the content of the XML file, add or remove the child elements or values, print the specific child attributes or the nodes, change the attribute values, etc. by providing the correct xpath syntax.

Start Your Free Software Development Course

Web development, programming languages, Software testing & others

Syntax;

For the non-windows target, ansible uses the module syntax community.general.xml, and for the windows target, ansible uses the win_xml module.

Parameters supported by the chúng tôi module.

Parameters:

add_children:

attribute:

The attribute to select when using the parameter value.

This is a string and not pretended with @.

backup:

choices: no (default) / yes

Create the backup file, including the timestamp of the backup. This module doesn’t take the backup automatically; we need to set the backup parameter to yes.

content: attribute/text

choices: attribute / text

count:

choices: no (default) / yes

Search for the given XPath and provide the count of any matches.

input_type:

choices: xml / yaml (default)

Type of the input for the add_children and set_children.

insertafter:

choices: no (default) / yes

It adds the additional child element(s) after the last element given in the Xpath.

Insertbefore:

choices: no (default) / yes

It adds the additional child element(s) before the first element given in the Xpath.

pretty_print:

choices: no (default) / yes

Pretty print xml output.

print_match:

choice: no (default) / yes

Search for the given Xpath and print any output that matches.

path:

aliases: dest / file

Path of the XML file as an input. If the XML string is not specified, then the path is required.

set_children:

To set the child element of the selected element from the given xpath.

state:

choices: absent/present

alias: ensure

Set or remove an xpath selection (node(s), attributes(s)).

value:

Desired state of the selected attribute.

xmlstring:

A string containing xml on which to operate. This parameter is necessary if the path is not provided.

xpath:

A valid xpath expression to describe the item(s) to manipulate, and it operates on the document root (/) by default.

How XML works in Ansible?

To deal with the XML files, we need the ansible XML module, and it doesn’t come with the ansible default installation, but we need to install it.  It is available as a part of the Ansible community.

To install the XML module, we can use the below command. This will install the XML for both the Unix and the Windows operating systems.

ansible-galaxy collection install community.general

For the Windows operating system, you can use the win_xml module, and for the non-windows target, you can use the chúng tôi module

When you work with the XML file, you need to provide the xPath to deal with the XML attributes and the values. You can learn more about the xPath notations from the websites below.

There are also many other websites you can refer to. For this example, we will use the sample XML file from Microsoft.

Playbook example:

Examples

Let us discuss examples of Ansible XML.

Example #1: Ansible XML module to count the number of attribute nodes

In this playbook, we will count the total number of author nodes.

Output:

There are a total of 12 “author” nodes.

Example #2: Remove the specific node with the attribute value

This playbook will remove all the nodes with the book id attribute bk101.

xpath: /catalog/book[@id=’bk101′] state: absent

Output:

Example #3: Playbook to remove attributes

This playbook will remove all the matching attributes. In this case, it will remove the ID attribute.

state: absent

Output:

Once you check the XML output, all the ids will be removed.

Example #4: Adding the new element with the value

This playbook will add the new element “Newbook” with the value “fiction”.

value: ’Fiction’

Output:

Example #5: Playbook to change the attribute value

value: ’ComputerTech’

Output:

XML file output:

Example #6: Ansible playbook to add multiple child elements

This playbook will add the multiple child elements to the specified attributes of the book node.

xpath: /catalog/book[@id=’bk101′] - tag: ’1001′

Output:

XML file output:

If you need to insert before the specific element, then use the insertbefore parameter. For example,

xpath: /catalog/book[@id=’bk101′]/genre[text() = ”Computer”] - tag: ’1001′

XML Output:

And for the insert after some attribute, you need to specify insertafter parameter.

- tag: ’1001′

Conclusion

XML file is used by the various websites, software, configurations, etc. and ansible uses the various parameters to read the content, copy the XML file, manipulate the XML file as per the requirement which helps when you configure any website or software using XML then you can use the builtin plugin to work with the XML file.

Recommended Articles

This is a guide to Ansible XML. Here we discuss the Definition, syntax, parameters, How XML works in Ansible? with Examples with code implementation. You may also have a look at the following articles to learn more –

You're reading How Xml Works In Ansible?

Learn How Untar Works In Ansible With Examples

Introduction to Ansible untar

Ansible untar module also known as unarchive for Unix OS or win_zip for the windows operating system is used to extract or unpack the archive files or folders on the remote destination by copying the archive file first by default on the remote server and also supports many parameters to deal with the unarchive or win_zip functionality like the owner, dest, exclude and more.

Start Your Free Software Development Course

Web development, programming languages, Software testing & others

Syntax

For the non-windows target unarchive or ansible.builtin.unarchive command uses the below syntax. We have shown the basics parameters

Parameters:

copy: No / Yes (Default)

The default Option is Yes and it copies the files from the local controller to the remote host if specified yes or nothing specified. For working with the remote source need to specify the remote_src and this copy parameter is not helpful there.

src (required):

Source path of the file. If remote_src is ‘yes’ then the source path would be on the remote location otherwise the source path is on the local controller node.

dest (required):

Remote server absolute path where the archive is going to extract.

remote_src: no (Default) / yes

If set ‘yes’ specifies that the source archive path is on the remote computer. For the ‘no’ value the path is on the local controller node.

owner:

name of the user that should own the files/directory after unpack and same replicates (added) to the chown.

group:

Name of the group that should own the files/directory and same replicates (added) to the chown.

exclude:

List of files or directories that need to be excluded from the unpacking.

include:

List of files or directories that need to be included in the unpacking process.

keep_newer: no (default) / yes

If set yes, it replaces the existing files that are newer than the files inside the archive.

mode:

Permissions that the files or directories should have after unpacked (like 644, 777, etc).

For the windows target src, dest, creates parameters remain the same as unarchive module and the additional parameters are as below.

Parameters:

delete_archive: no (default) / yes

Removes the zip file after unzipping.

password

If the Zip file is password encrypted then this parameter is useful and it requires the PSCX module to be installed.

recurse: no (default) / yes

recursively expands the zip file within the src directory.

Setting value ‘yes’ requires the PSCX module to be installed.

Please note: the win_unzip module doesn’t use the remote_src parameter.

How untar works in Ansible?

Ansible unarchive module for non-windows target comes with the ansible-base and so it is included in the Ansible installations. For the windows target, we need to use the win_unzip module. If the module is not available then you can download it from the galaxy.

ansible-galaxy collection install community.windows

Below is the simple playbook for windows untar (unzip).

dest: c:temp7zipInstaller

Output:

The above playbook will unzip the file from the source location to the destination remote servers. If the destination path doesn’t exist it creates the destination path.

You must have noticed here, although the source path is remote, we don’t need to use remote_src because the win_unzip module doesn’t support it and when we use the remote source path for the non-target windows server we must specify the remote_src. For example,

remote_src: yes

Examples

Here are the following examples mention below

Example #1 – unarchive module task for UNIX os.

dest: /tmp/phyes

In this playbook, it will retrieve the chúng tôi file to the destination remote host /tmp/phyes. Before running this task unlike the win_unzip module, you need to make sure that the destination path exists otherwise it will throw an error.

Output:

Example #2 – Exclude files from the archive.

To exclude the certain file from the unpacking we can use h

Code:

exclude: ’Test1 document.txt’

If there are multiple files to exclude then you can provide the list as below.

- ’sourcefile.py’

Example #3 – Include files from the archive

Code:

include: ’Test1 document.txt’

The above playbook will include only the test1 text file and to include the multiple documents, use the below command.

- ’sourcefile.py’

Example #4 – using multiple parameters together.

Code:

owner: ansibleadmin

In the above playbook, it will include only 2 files, keep_newer parameter will not replace the existing files that are newer than files from the archive, remote_src indicates the remote source and it will set the owner permission on the files and it will keep the file permission 0644.

Conclusion

Untar or unarchive or unzip modules are very useful when we write the playbook. It makes it easier to extract the files or folders on the destination server without using any third-party software and in addition, it uses various parameters like we don’t need to copy the file before extracting, adding permissions after extract, etc.

Recommended Articles

This is a guide to  Ansible untar. Here we discuss How untar works in Ansible and Examples along with the codes and outputs. You may also look at the following articles to learn more –

Guide On How Does Ansible Synchronize Works

Introduction to Ansible Synchronize

Web development, programming languages, Software testing & others

Explaining the Ansible Synchronize

Ansible synchronizes work like rsync in many ways. But we must remember the below points while using it in our environments. These will explain this module and show its limitations:

To work with this module, rsync must be installed on both source and target systems.

By default, the source of files is localhost i.e. the controller machine and destination of files is the machine where the connection is made to transfer files. This default feature can be changed by using parameter delegate_to, which allows you to change your source from localhost to some other host. Thus you can copy files from a remote machine to another remote machine.

On synchronize source machine, file’s permissions are of the user who is running the tasks on localhost or remote_user in the case when delegate_to is used.

On synchronize destination machine, the file’s permission will be of remote_user on destination host or of become_user if become=yes is given in parameters, but to elevate the permission, password less sudo should be set up, as rsync itself does not give a way to pass sudo credentials.

Currently, we have only below few connection types to work with Ansible synchronize viz are ssh, paramiko, local, and docker.

Always give the full path of the destination host location, as there may be cases where you used sudo, but files will be copied to remote_user home directory.

Linux rsync limitations related to hard links are also applied here.

Ansible synchronizes module forces -delay-updates to avoid the broken state in case of connection failure.

How does Ansible Synchronize Works?

Ansible synchronize user below parameters and their acceptable values are listed as below. Using the combination of these parameters, we can decide the behavior and output of Ansible synchronize.

archive: The acceptable values are yes and no. The default value is set to yes. This mirrors the rsync flag, enable recursive, links, perm, group, owner, time flag.

hecksum: The acceptable values are yes and no. The default value is set to no. This is used to skip based on checksum.

compress: The acceptable values are yes and no. The default value is set to yes. This is used to compress files during transfer to speed up the transfer.

copy_links: The acceptable values are yes and no. The default value is set to no. This is used to copy the referenced items rather than links.

delete: The acceptable values are yes and no. The default value is set to no. This is used to delete files in dest location, which does not exist on the source somehow when the transfer is completed. This works when recursive=yes is set.

dest: The absolute or relative path on the destination machine. Which will be synced from the source.

src: The absolute or relative path on the source machine. Which will be synced from the destination.

dirs: The acceptable values are yes and no. The default value is set to no. This is used to transfer directories without recursive.

dest_port: Port number of ssh on destination.

link_dest: Default value is null. This is used to add a destination to hard links against during the rsync.

links: This is used to copy syslinks as syslinks, not referenced items.

mode: Acceptable values are push and pull. The default value is push.

owner: The acceptable values are yes and no. This is used to preserve owner.

rsync_path: This is used to specify the rsync command path on remote hosts.

times: To preserve the modification times. The acceptable values are yes and no.

Examples of Ansible Synchronize

Now by using examples, we will try to learn about Ansible synchronize, which you might have to use in day to day operations. We will take some examples, but before going there, we first understand our lab, we used for testing purpose. Here we have an Ansible control server named ansible-controller and few remote hosts named host- remote, host-one, and host-two. We will create playbooks and run Ansible commands on the ansible- controller node and see the results on the remote hosts.

In this example, we will do the synchronization of files from source machine viz. Ansible controller node to the remote host. We have a set of files under /var/tmp/sync_folder on the Ansible controller node which will be transferred to remote host via Ansible synchronize module. For this we have a playbook like below:

src: /var/tmp/sync_folder dest: /var/tmp/

ansible-playbook ansible_synchronize.yaml

ls -l

In this example, we will do the synchronization of files from one remote host to another remote host. For this we have a playbook like below:

src: /var/tmp/sync_folder dest: /var/tmp/ delegate_to: host-two

On the remote machine, we can cross-check to confirm the files have been transferred.

ls -l

Conclusion

As we saw, Ansible synchronize is powerful but easy to use the module, but we must also acknowledge that this is not the replacement of rsync in Linux systems. So keeping in mind, you must also remember all the limitations mentioned above in this article to avoid unexpected outcomes. So learn it first and then use it carefully.

Recommended Articles

This is a guide to Ansible Synchronize. Here we also discuss the Introduction and how does ansible synchronize works along with examples and its code implementation. You may also have a look at the following articles to learn more –

How Does Date Function Work In Xml With Examples?

Definition on XML Date

XML Date is defined as a data type to specify the date in the XML Documents. According to W3C XML Schema, a date is a period of one day in its time zone. The date rule could be customized according to the requirements where sometimes it is necessary to do some date operations or parse dates to a specific format provided time zone should be specified if not local time is used. And the date format is defined by date pattern Strings by assigning letters from A to Z.

Start Your Free Software Development Course

Web development, programming languages, Software testing & others

In this article, we have used a Class XML Gregorian Calendar for the data Utilities.

Syntax

The XML format for Date is given in the following formats

CCYY-MM-DD

Where the data type specifies Year, Month, and Day. It’s a finite-length sequence of characters with yy-mm-dd. The four-digit numeric represents a year, the negative value is restricted, and the year 0000 is neglected. And there is a symbol ‘- ‘separator between this format; finally, two-digit numerals signify month and date.

The element declaration is illustrated as

The current date on Xpath is defined as

xs:date fn:current-date() How does Date function work in XML?

Generally, this Date function includes Data types like

xs:dateTime (CCYY-MM-DDThh:mm:ss)

xs:date (CCYY-MM-DD)

xs:time (hh:mm:ss)

xs:gYearMonth (CCYY-MM)

xs:gYear (CCYY)

xs:gMonthDay (–MM-DD)

xs:gMonth (–MM–)

xs:gDay (—DD)

and XML formatter prefers to use Simple Date Format, and it is not thread-safe. Also, this constructor is not supported in all the local files. The format comes like this:

public SimpleDateFormat(String pattern, DateFormatSymbols formatSymbols)

The Gregorian Calendar is specified as

2011-11-21

2011-11-21 +02:00

2011-11-21 Z

2011-11-21+00:00

2011-11-21

2011-02-03

The value of the datetime given is parsed by the XML parser, which converts the datetime value declared in the input XML to the value of the local time zone format. Thus, even a daylight-saving option could be made.

Using the Current date() function to display the current date of that day. This function is called without passing any parameters. As a result, it returns the date manipulated from the System time, i.e., gives out a constant value. Let’s see a simple working code of the XSD file.

<xsl: stylesheet version=”2.0″ The current date today is:

And in Xpath, we have like

And Few functions on Date are dateTime (), year-from-dateTime (), year-from-date(date), month-from-date(date) , day-from-date(date).

Next, for the sample XML schema, the customization of XML date and time is specified as

public class Client { @XmlElement(name = "dob") @XmlSchemaType(name = "date") protected XMLGregorianCalendar dateOfBirth; public XMLGregorianCalendar getDateOfBirth() {return dateOfBirth;} public void setDateOfBirth(XMLGregorianCalendar value) {this.dateOfBirth = value; } } Examples

Now let’s see how this function works well in XSLT and java.

Example#1 – Simple XML file displays the date

chúng tôi

Output:

Example#2

Educ.java

import java.time.LocalDateTime; import java.time.ZoneId; import java.time.ZonedDateTime; import java.time.format.DateTimeFormatter; import java.util.Date; import java.util.GregorianCalendar; import javaxxml.datatype.DatatypeConfigurationException; import javaxxml.datatype.DatatypeFactory; import javaxxml.datatype.XMLGregorianCalendar; public class Educ { private final static String TIMESTAMP_PATTERN = "MM/dd/yyyy hh:mm a z"; private final static DateTimeFormatter DATE_TIME_FORMATTER = DateTimeFormatter.ofPattern(TIMESTAMP_PATTERN); public static void main(String[] args) throws DatatypeConfigurationException { GregorianCalendar c = new GregorianCalendar(); c.setTime(new Date()); XMLGregorianCalendar xc = DatatypeFactory.newInstance() .newXMLGregorianCalendar(c); ZonedDateTime zon = xc.toGregorianCalendar().toZonedDateTime(); System.out.println( DATE_TIME_FORMATTER.format(zon) ); ZonedDateTime zond = zon.withZoneSameInstant(ZoneId.of("UTC")); System.out.println( DATE_TIME_FORMATTER.format(zond) ); } }

Explanation:

Output:

Example#3 – Showing java code to convert Date Object to String Value Using Gregorian Calendar

Rule.java

import java.time.LocalDateTime; import java.time.ZoneId; import java.time.ZonedDateTime; import java.time.format.DateTimeFormatter; import java.util.Date; import java.text.DateFormat; import java.text.SimpleDateFormat; import java.util.GregorianCalendar; import javaxxml.datatype.DatatypeConfigurationException; import javaxxml.datatype.DatatypeFactory; import javaxxml.datatype.XMLGregorianCalendar; public class Rule { public static void main(String[] args) throws DatatypeConfigurationException { GregorianCalendar gca = new GregorianCalendar(); gca.setTime(new Date()); XMLGregorianCalendar xgc = DatatypeFactory.newInstance().newXMLGregorianCalendar(gca); System.out.println(convertXmlGregorianToString(xgc)); } public static String convertXmlGregorianToString(XMLGregorianCalendar xgc) { DateFormat datef = new SimpleDateFormat("MM/dd/yyyy hh:mm a z"); GregorianCalendar gCalendar = xgc.toGregorianCalendar(); Date dd = gCalendar.getTime(); String dStr = datef.format(dd); return dStr; } } 

Explanation:

The above java code converts an XML file document into java code by converting their data objects to display date. It uses simple packages like Date Format and Simple Date Format.

Output:

Example#4 – Using a Style sheet to give out the date.

.xsl

chúng tôi

Explanation:

Here we have used an XML file with various elements, and XSLT is created,

Output:

Example#5 – Xml date using C#

Code:

using System; using System.IO; using System.Xml; public class test { public static void Main() { Int16 cid = 3252; String oID = "3524f5"; DateTime orderDate = new DateTime(); orderDate = DateTime.Now; Double price = 20.95; XmlTextWriter writer = new XmlTextWriter (Console.Out); writer.Formatting = Formatting.Indented; writer.WriteStartElement("order"); writer.WriteAttributeString("date", XmlConvert.ToString(orderDate, "yyyy-MM-dd")); writer.WriteAttributeString("time", XmlConvert.ToString(orderDate, "HH:mm:ss")); writer.WriteElementString("orderID", oID); writer.WriteElementString("custID", XmlConvert.ToString(cid)); writer.WriteElementString("price", XmlConvert.ToString(price)); writer.WriteEndElement(); writer.Close(); } }

Explanation:

The above code automatically generates the current date from the System, which is shown below. The XML is written using the writer methods, where it starts from the root element ‘order.’

Output:

Conclusion

Therefore this article shows how to apply Date Format value types in java and also taught us the customization formats by changing the different settings as explained in the working sections.

Recommended Articles

This is a guide to XML Date. Here we discuss how the XML date function works well in XSLT and java, along with different examples and its code implementation. You may also have a look at the following articles to learn more –

How To Create An Xml Sitemap

A step-by-step Guide to producing chúng tôi to help Google crawl your content

An XML (Extensible Mark-up Language) sitemap is a form of markup language and is consisted of tags that define pages that should be indexed by search engines.

In this simple way we can easily identify if companies have a chúng tôi and if the values in the tags, for each page, are properly implemented. These are some important tips that you need to consider when deciding whether to use XML Sitemaps.

The XML optimisation will help us boost the indexation process of the site amongst search engine spiders by highlighting new and priority content.

However, XML sitemaps are not essential since Google robots (spiders) will access different content by following links between pages and they will return to access new content. Google can’t rely on every site having a sitemap.

An XML Sitemap helps search engine spiders understand which pages are more important than others by setting a priority.

It is important to update the chúng tôi every time we create a new page in our website.

An XML sitemap can help you review which pages on different sections of a site are indexed or unavailable using Google Webmaster Tools.

Ideally we need to generate a sitemap for all pages of the site, by editing their priority and frequency. According to how important each page is in terms of Frequency (e.g. Daily, Weekly, Monthly etc.) and Priority (e.g. 0.75, 0.64, 0.25 etc.) the respective amendments should be made.

 Why suggest Frequency and Priority of each Page? Because in this way search engine spiders will be able to understand which page is actually more important than the other and in this way they will be able to allocate their (namely search engine spiders) budget by crawling more often the pages that are actually important, rather than spending their budget to less important pages.

The Sitemap HTML (not XML) includes links; it is designed for users (it’s actually a page within the website) who want to navigate through the website.

According to Google, there isn’t a guarantee that all pages will be crawled and indexed, but Google uses all the data that we provide them (e.g. last modification date, priority, frequency) in order to know more for the website’s structure.

We need to ensure that the URLs are clean and descriptive.

If we have multi-lingual websites, then we will need to generate the chúng tôi in each language respectively as in the Dell site.

Without any further ado, we can now review the step-by-step process in order to generate a sitemap.

STEP 1 – Use of chúng tôi Generator

STEP 2 – Download the XML Sitemap

Once we choose to download the un-compressed XML Sitemap we will have this chúng tôi ready (as we see on the screenshot below)  that we will need to further edit (Priority and Frequency) . 

STEP 3 – Selecting the right editing tool

In order to start modifying the current Frequency and Priority, all we need to is to start using the NotePad ++. It’s a user-friendly software that can be installed on the desktop of our computers and facilitate our life regarding the editing of the sitemap.xml.

All we have to do now is to save the current form of the chúng tôi on our desktop on a folder and start working on the Notepad ++ in order to edit the Frequency and Priority of each page.

STEP 4 –  chúng tôi Editing

Important Tip:

For our case study, we have deliberately deleted a tag. In this case the final chúng tôi will appear like this (please review the screenshot below) and we will probably need to review again the chúng tôi until we spot the problem.

An extra tip for multilingual websites

STEP 5 – Finalising the Sitemap XML

After the editing of the chúng tôi (you can see the final version of the chúng tôi below), the next step is the implementation of the chúng tôi in the source code. Depending on our coding skills we can either implement it ourselves or a developer can implement it instead.

Implementation of chúng tôi on Google Webmaster Tools

Once the chúng tôi is implemented by the development team, we will have to submit each language version of the website on Google Webmaster Tools (and on Bing Webmaster Tools).

Where are we going to find the respective Sitemap section?

Afterwards, just fill out the respective field and you are ready to submit the website to Google Webmaster Tools.

Important Tip – Implementation of chúng tôi on Google Webmaster Tools for multilingual websites

Arrange our Site Settings (the Geographic Target, or Geotarget) in each language version (e.g. com/de for Germany, com/ru for Russia, com/fr for France, com/it for Italy).

Create a separate chúng tôi one for each language version.

I hope these steps give you an idea of how sitemaps can be setup if you have heard about them, but wondered how to set them up.

Learn How Does Either Works In Haskell?

Introduction to Haskell either

In Haskell either is used to represent the possibility of two values. Either is used to represent two values that can be correct or error. It has two constructors also which are named Left and Right. These constructors also represent and show some purpose either in Haskell. Here Left constructor will show the error value, while on the other hand Right constructor will show the correct value. In the coming section of the tutorial, we will see how this function works in Haskell in more detail, and also we will see its implementation and usage while doing programming in Haskell.

Start Your Free Software Development Course

Web development, programming languages, Software testing & others

In this section we will see the syntax for either in Haskell, which is given by their official documentation, let’s have a closer look at the syntax of it for better understanding see below;

data Either a b

As you can see in the above line of syntax we have its basic definition with us. Here we are using either keyword followed by two values ‘a’ and ‘b’. Let’s have a look at the practice syntax for either, which will be more helpful to get a better idea for either in Haskell for beginners to see below;

Example:

let variable_name = Your_constructor "value if any" :: Either a basic How does either work in Haskell?

As we already know that either is used to represent two values which can be either correct or error. It also contains two constructors which further used to represent these values in Haskell either. So by the use of either, we can represent our value which is either correct or error. In this section we will first see its definition by the Haskell documentation to get a better idea, let’s get started to see below;

Method signature:

As you can see in the above line of definition for either in Haskell, is given by the Haskell official documentation. This is available inside the Data library, so we can use it as Data.eithe in Haskell. Also if we can see this closely we have two values here ‘a’ and ‘b’. These values are represented by the Left and Right constructor which will turn represent the value as correct and error. After the ‘=’ operator in the above definition, we are trying to represent the ‘a’ value by the Left constructor, and ‘b’ values is represented by the Right constructor. Below we will see the detailed description of both these constructors for better understanding see below;

Available Constructor:

1. Left: As per the official documentation of the Haskell, and as per the convention Left constructor in either is used to represent the error value. Below see the syntax to use it for better understanding see below;

Example:

Left a

1. Right: As per the official documentation of Haskell, and as per the convention Right constructor in either is used to represent the correct value. Below see the syntax to use it for better understanding see below;

Example:

Right a

1. isRight: This method is used to check whether we have passed the right value or not. It will return us the Boolean true or false. If the value if Right value then it will return true else it will return false. Below see the definition of the method as per the Haskell documentation for better understanding see below;

Example:

Now we will see one practice syntax how we can use this while programming in Haskell;

Example:

isRight (Right "your value ")

As you can see in the above line of code we are using the isRight method followed by the Right value passed inside the bracket. In this way, you can use it to evaluate the result of the passed value.

2. isLeft: This method is used to check whether we have passed the left value or not. It will return us the Boolean true or false. If the value is Left value then it will return true else it will return false. Below see the definition of the method as per the Haskell documentation for better understanding see below;

Example:

Example:

isLeft (Left "your value ")

As you can see in the above line of code we are using the isLeft method followed by the Left value passed inside the bracket. In this way, you can use it to evaluate the result of the passed value.

Examples

1. In this example we are trying to identify the value as string or int by using the either Left and Right constructor available. Remember if you want to use either while programming does not forget to import this in your program otherwise it will not work.

Example:

import Data.Either main = do print("Demo to show wokring of either in Haskell !!") print("Using either to evaluate the value either instance of string or inte using either in Haskell !!") let val1 = Left "Hello" :: Either String Int let val2 = Right 100 :: Either String Int let val3 = Left "Hellow world" :: Either String Int let val4 = Left "I m string !!" :: Either String Int let val5 = Right 900 :: Either String Int let val6 = Left "I am another string" :: Either String Int let val7 = Right 500 :: Either String Int print("Printing the result after either evalution !!") print("result one is :: ", val1) print("result two is :: ", val2) print("result three is :: ", val3) print("result four is :: ", val4) print("result five is :: ", val5) print("result six is :: ", val6) print("result seven is :: ", val7)

Output:

Conclusion

By the use of either in Haskell we can easily identify the passing value is correct or error. We also have so many methods available which can be used either to get the result fast for passing Right and Left value in Haskell. Mainly it is used to show the possibility between the two values either a or b.

Recommended Articles

We hope that this EDUCBA information on “Haskell either” was beneficial to you. You can view EDUCBA’s recommended articles for more information.

Update the detailed information about How Xml Works In Ansible? on the Kientrucdochoi.com website. We hope the article's content will meet your needs, and we will regularly update the information to provide you with the fastest and most accurate information. Have a great day!