Tutorial by Examples: ed

Use 403 Forbidden when a client has requested a resource that is inaccessible due to existing access controls. For example, if your app has an /admin route that should only be accessible to users with administrative rights, you can use 403 when a normal user requests the page. GET /admin HTTP/1.1 ...

In order to efficiently handle cycle detection, we consider each node as part of a tree. When adding an edge, we check if its two component nodes are part of distinct trees. Initially, each node makes up a one-node tree. algorithm kruskalMST'(G: a graph) sort G's edges by their value MST ...

The above forest methodology is actually a disjoint-set data structure, which involves three main operations: subalgo makeSet(v: a node): v.parent = v <- make a new tree rooted at v subalgo findSet(v: a node): if v.parent == v: return v return findSet(v.parent...

We can do two things to improve the simple and sub-optimal disjoint-set subalgorithms: Path compression heuristic: findSet does not need to ever handle a tree with height bigger than 2. If it ends up iterating such a tree, it can link the lower nodes directly to the root, optimizing future trav...

The DOM (Document Object Model) is the programming interface for HTML and XML documents, it defines the logical structure of documents and the way a document is accessed and manipulated. The main implementers of the DOM API are web browsers. Specifications are standardized by the W3C and the WHATW...

Use associated type when there is a one-to-one relationship between the type implementing the trait and the associated type. It is sometimes also known as the output type, since this is an item given to a type when we apply a trait to it. Creation trait GetItems { type First; // ^~~~ d...

<div tabindex="2">Second</div> <div tabindex="1">First</div> Positive values will insert the element at the tabbing order position of its respective value. Elements without preference (i.e. tabindex="0" or native elements such as button and a...

We can optimize a simple xor function for only architectures that support unaligned reads/writes by creating two files that define the function and prefixing them with a build constraint (for an actual example of the xor code which is out of scope here, see crypto/cipher/xor.go in the standard libra...

The hashlib module allows creating message digest generators via the new method. These generators will turn an arbitrary string into a fixed-length digest: import hashlib h = hashlib.new('sha256') h.update(b'Nobody expects the Spanish Inquisition.') h.digest() # ==> b'.\xdf\xda\xdaVR[\x12\...

This method looks for the existence of browser specific things. This would be more difficult to spoof, but is not guaranteed to be future proof. // Opera 8.0+ var isOpera = (!!window.opr && !!opr.addons) || !!window.opera || navigator.userAgent.indexOf(' OPR/') >= 0; // Firefox 1.0+ ...

#include <stdio.h> #include <stdlib.h> int main (void) { int * pdata; size_t n; printf ("Enter the size of the array: "); fflush(stdout); /* Make sure the prompt gets printed to buffered stdout. */ if (1 != scanf("%zu", &n)) /* If zu is n...

Whitespace is handled by the lexical analyzer before being parsed. The lexical analyzer uses a stack to store indentation levels. At the beginning, the stack contains just the value 0, which is the leftmost position. Whenever a nested block begins, the new indentation level is pushed on the stack, ...

Creating a custom directive with isolated scope will separate the scope inside the directive from the outside scope, in order to prevent our directive from accidentally change the data in the parent scope and restricting it from reading private data from the parent scope. To create an isolated scop...

Functions in python are first-class objects. They can be defined in any scope def fibonacci(n): def step(a,b): return b, a+b a, b = 0, 1 for i in range(n): a, b = step(a, b) return a Functions capture their enclosing scope can be passed around like any other...

Below won't work on a Windows machine $file = $request->file('file_upload'); $sampleName = 'UserUpload'; $destination = app_path() . '/myStorage/'; $fileName = $sampleName . '-' . date('Y-m-d-H:i:s') . '.' . $file->getClientOriginalExtension(); $file->move($destination, $fileName); ...

This query gets all books with ratings greater than or equal to zero and less than six. all_books = Book.objects.filter(ratings_range_contained_by=(0, 6))

the timedelta module comes in handy to compute differences between times: from datetime import datetime, timedelta now = datetime.now() then = datetime(2016, 5, 23) # datetime.datetime(2016, 05, 23, 0, 0, 0) Specifying time is optional when creating a new datetime object delta = now-then ...

To generate a list (tree view) of currently installed packages, use npm list ls, la and ll are aliases of list command. la and ll commands shows extended information like description and repository. Options The response format can be changed by passing options. npm list --json json - Sh...

Removing duplicate values in a list can be done by converting the list to a set (that is an unordered collection of distinct objects). If a list data structure is needed, then the set can be converted back to a list using the function list(): names = ["aixk", "duke", "edik&...

MySQL's DELETE statement can use the JOIN construct, allowing also to specify which tables to delete from. This is useful to avoid nested queries. Given the schema: create table people ( id int primary key, name varchar(100) not null, gender char(1) not null ); insert people (id,na...