Tutorial by Examples: g

The "right-left" rule is a completely regular rule for deciphering C declarations. It can also be useful in creating them. Read the symbols as you encounter them in the declaration... * as "pointer to" - always on the left side [] as "array of" ...

A goto statement transfers control to the statement with the corresponding label within the same function. Executing the goto statement must not cause any variables to come into scope that were not already in scope at the point of the goto. for example see the standard library source code: https:/...

WeakMap object allows you to store key/value pairs. The difference from Map is that keys must be objects and are weakly referenced. This means that if there aren't any other strong references to the key, the element in WeakMap can be removed by garbage collector. WeakMap constructor has an optional...

To get a value associated to the key, use the .get() method. If there's no value associated to the key, it returns undefined. const obj1 = {}, obj2 = {}; const weakmap = new WeakMap([[obj1, 7]]); console.log(weakmap.get(obj1)); // 7 console.log(weakmap.get(obj2)); // undefined

To assign a value to the key, use the .set() method. It returns the WeakMap object, so you can chain .set() calls. const obj1 = {}, obj2 = {}; const weakmap = new WeakMap(); weakmap.set(obj1, 1).set(obj2, 2); console.log(weakmap.get(obj1)); // 1 console.log(weakmap.get(obj2)); // 2 ...

To check if an element with a specified key exits in a WeakMap, use the .has() method. It returns true if it exits, and otherwise false. const obj1 = {}, obj2 = {}; const weakmap = new WeakMap([[obj1, 7]]); console.log(weakmap.has(obj1)); // true console.log(weakmap.has(obj2)); // false...

To remove an element with a specified key, use the .delete() method. It returns true if the element existed and has been removed, otherwise false. const obj1 = {}, obj2 = {}; const weakmap = new WeakMap([[obj1, 7]]); console.log(weakmap.delete(obj1)); // true console.log(weakmap.has(obj...

To use SQL syntax with model, that would transfer result to proper instantions, you should use directly one of Phalcon\Mvc\Model\Resultset classes: $users = new \Application\Models\Users(); // bitwise operation on `flag` field $sql = 'SELECT * FROM phorum.users WHERE (15 & (1 <&...

Recommendation Because the symbols i and j can represent significantly different things in MATLAB, their use as loop indices has split the MATLAB user community since ages. While some historic performance reasons could help the balance lean to one side, this is no longer the case and now the choice...

You could use "SP_HELPINDEX Table_Name", but Kimberly Tripp has a stored procedure (that can be found here), which is better example, as it shows more about the indexes, including columns and filter definition, for example: Usage: USE Adventureworks EXEC sp_SQLskills_SQL2012_helpindex ...

In the above example, if we want to send out HTML content as message in the email, then create a HTML file by going to File -> New -> HTML file Now you can see a HTML file besides your gs file as follows : Now, update the getMessage() method from above example as follows : function getMes...

A simple PL/pgSQL function: CREATE FUNCTION active_subscribers() RETURNS bigint AS $$ DECLARE -- variable for the following BEGIN ... END block subscribers integer; BEGIN -- SELECT must always be used with INTO SELECT COUNT(user_id) INTO subscribers FROM users WHERE subscribed...

You can iterate over the contents of a dictionary with dict for, which is similar to foreach: set theDict {abcd {ab cd} bcde {ef gh} cdef {ij kl}} dict for {theKey theValue} $theDict { puts "$theKey -> $theValue" } This produces this output: abcd -> ab cd bcde -> ef gh c...

Sometimes you need to match a literal (sub-)string with a regular expression despite that substring containing RE metacharacters. While yes, it's possible to write code to insert appropriate backslashes to make that work (using string map) it is easiest to just prefix the pattern with ***=, which ma...

Marshal class contains a function named PtrToStructure, this function gives us the ability of reading structures by an unmanaged pointer. PtrToStructure function got many overloads, but they all have the same intention. Generic PtrToStructure: public static T PtrToStructure<T>(IntPtr ptr); ...

SYS_REFCURSOR can be used as a return type when you need to easily handle a list returned not from a table, but more specifically from a function: function returning a cursor CREATE OR REPLACE FUNCTION list_of (required_type_in IN VARCHAR2) RETURN SYS_REFCURSOR IS v_ SYS_REFCURSOR; BEGIN...

Declare the cursor to scan a list of records Open it Fetch current record into variables (this increments position) Use %notfound to detect end of list Don't forget to close the cursor to limit resources consumption in current context -- DECLARE CURSOR curCols IS -- select column name a...

You can override the default vmoptions with your own personal settings by choosing Help > Edit Custom VM Options from the toolbar. This will create a local copy of the file which you are free to edit. For example, if you double the value set for Xmx, the maximum size of the memory allocation poo...

This example shows the base of almost any XSLT transformation and the most fundamental XSLT design pattern. Producing as output an XML document that is identical to the source XML document. Source XML document: <t>Hello, World!</t> XSLT transformation: <xsl:stylesheet version=&q...

A downcast can be used to make use of a subclass's code and data inside of a function taking a parameter of its superclass. class Rat { var color = "white" } class PetRat: Rat { var name = "Spot" } func nameOfRat(🐭: Rat) -> String { guard let petRat = ...