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Articles on Trending Technologies
Technical articles with clear explanations and examples
What is Handle?
A handle is a substring that connects a right-hand side of the production rule in the grammar and whose reduction to the non-terminal on the left-hand side of that grammar rule is a step along with the reverse of a rightmost derivation.Finding Handling at Each StepHandles can be found by the following process −It can scan the input string from left to right until first .> is encountered.It can scan backward until
Read MoreWhat are Precedence Relations in Operator Grammar?
For terminals a and b in an Operator Grammar we can have the following precedence Relations −a =. b(Equal Precedence) − If R.H.S of production is of form α a β b γ, where β can be ε or single non-terminal then a =. b.Here, α and γ can be any strings.Example − In grammar, S → m A c B e dOn Comparing mAcBed with αaβbγα = mA, a = c, β = B, b = e, γ = dΑAβbγmACBedSo, comparing a with c and b with e we get c =.e.We can also make a different combination for ...
Read MoreWhat are LEADING and TRAILING operation of an operator precedence grammar?
LEADINGIf production is of form A → aα or A → Ba α where B is Non-terminal, and α can be any string, then the first terminal symbol on R.H.S isLeading(A) = {a}If production is of form A → Bα, if a is in LEADING (B), then a will also be in LEADING (A).TRAILINGIf production is of form A→ αa or A → αaB where B is Non-terminal, and α can be any string then, TRAILING (A) = {a}If production is of form A → αB. If a is in TRAILING (B), then a will be in TRAILING (A).Algorithm to ...
Read MoreNode.js – Immediate Timer Class
The Immediate Timer class is used for scheduling the functions that we need to call at a certain period of time in future. These tasks can be scheduled by using the Immediate timer class and using the setImmediate() method. The Immediate class has an object for setImmediate() method and it passes the same object to clearImmediate() in case it wants to cancel the scheduled timer function.Given below are the Immediate class ref objects −1. immediate.ref()This method is called if the immediate object is active for too long and did not exit.Syntaximmediate.ref()2. immediate.unref()This object keeps the event loop ‘active’ until False ...
Read MoreNode.js – diffieHellman.getPublicKey() Method
The diffieHellman.getPublicKey() returns the Diffie-Hellman generated public key that is specified by the encoding passed. It will return a string in case the encoding is passed, else it will return a buffer.SyntaxdiffieHellman.getPublicKey([encoding])Parametersencoding – This parameter specifies the encoding of the return value.Example 1Create a file with the name "publicKey.js" and copy the following code snippet. After creating the file, use the command "node publicKey.js" to run this code.// diffieHellman.getPublicKey() Demo Example // Importing the crypto module const crypto = require('crypto') // Initializing the diffieHellman const dh = crypto.createDiffieHellman(512); // Taking default publicKey as null let publicKey = ...
Read MoreNode.js – Timeout-hasRef() & Timeout-refresh() methods
The Timeout object is internally created and is returned from the setTimeout() and setInterval() method. You can use this object and pass it to either clearTimeout() or clearInterval() methods in order to cancel the scheduled actionsFollowing are the timeout class ref objects that can be used to control the default behaviour1. timeout.hasRef()This method keeps the node event loop active as long as its value is True.Syntaxtimeout.hasRef()2. timeout.refresh()This method refreshes the timer’s start time to the current time and reschedules the timer to its callback where the previously specified duration will be adjusted to the current time. This method helps in ...
Read MoreWhat is Operator Precedence Parsing?
Operator Precedence Parsing is also a type of Bottom-Up Parsing that can be used to a class of Grammars known as Operator Grammar.A Grammar G is Operator Grammar if it has the following properties −Production should not contain ϵ on its right side.There should not be two adjacent non-terminals at the right side of production.Example1 − Verify whether the following Grammar is operator Grammar or not.E → E A E |(E)|idA → +| − | ∗SolutionNo, it is not an operator Grammar as it does not satisfy property 2 of operator Grammar.As it contains two adjacent Non-terminals on R.H.S of ...
Read MoreNode.js – process.channel Property
When a node process is spawned with an IPC channel, the process.channel property provides the reference to that IPC channel. If no IPC channel exists, this property is then undefined.Syntaxprocess.channelExample 1Create two files "channel.js" and "util.js" and copy the following code snippets. After creating the files, use the commands "node channels.js" and "node util.js" to run the codes.channel.js// process.channel Property Demo Example // Importing the process modules const cp = require('child_process'); // Getting reference to the child const process = cp.fork(`${__dirname}/util.js`); // Sending the below message to child process.send({ msg: 'Welcome to Tutorials Point' }); console.log(process.channel)util.js// ...
Read MoreNode.js – dnsPromises.resolve4() Method
The dnsPromises.resolve4() method uses the DNS protocol to resolve IPv4 addresses (A records) for the hostname. A promise is resolved with an array of IP addresses when True.The difference between the dnsPromises and dns module is that dnsPromises provides an alternative way to asynchronous DNS methods that return Promise objects instead of callbacks.Syntaxdns.resolve4(hostname, [options])Parametershostname – This parameter takes input for hostname to be resolved.options – It can have the following options −ttl – This defines the Time-To-Live (TTL) for each record. Callback receives an array of addresses like this – { address: ‘1.2.3.4’, ttl:60 }Example 1Create a file "resolve4.js" and ...
Read MoreNode.js – dns.resolveNaptr() Method
The dns.resolveNaptr() method uses the DNS protocol to resolve regular expression based words (NAPTR records) for the hostname. The addresses argument passed to the callback function will contain an array of objects with the following properties −flagsserviceregexpreplacementorderpreferenceSyntaxdns.resolveNaptr(hostname, callback)Parametershostname – This parameter takes input for the hostname to be resolved.callback – This function will catch errors, if any.Records – Returns NAPTR records for the hostname.Example 1Create a file "resolveNaptr.js" and copy the following code snippet. After creating the file, use the command "node resolveNaptr.js" to run this code.// dns.resolveNaptr() Demo Example // Importing the dns module const dns = require('dns'); ...
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