Tutorial by Examples: al

By default, Django renders ForeignKey fields as a <select> input. This can cause pages to be load really slowly if you have thousands or tens of thousand entries in the referenced table. And even if you have only hundreds of entries, it is quite uncomfortable to look for a particular entry amo...

In a non-strict-mode scope, when a variable is assigned without being initialized with the var, const or the let keyword, it is automatically declared in the global scope: a = 12; console.log(a); // 12 In strict mode however, any access to an undeclared variable will throw a reference error: &...

If you have a string that contains Python literals, such as strings, floats etc, you can use ast.literal_eval to evaluate its value instead of eval. This has the added feature of allowing only certain syntax. >>> import ast >>> code = """(1, 2, {'foo': 'bar'})&quot...

It is not possible to use eval or exec to execute code from untrusted user securely. Even ast.literal_eval is prone to crashes in the parser. It is sometimes possible to guard against malicious code execution, but it doesn't exclude the possibility of outright crashes in the parser or the tokenizer....

Detailed instructions on getting forms set up or installed.

First of all, you cannot "install" Java EE. Java EE consists of a number of specifications. You can install implementations of those specifications however. Depending on your needs, there are lots of possibilities. To install most (or all) of the specifications, you can choose a Java EE...

You can choose between major distributions of LaTeX: TeX Live (Windows, Linux, and OS X), the standard, cross-platform distribution. MacTeX (Mac) A packaged version of TeX Live made for OS X with some Mac-specific tools MiKTeX (Windows) A separate distribution entirely that All distributions...

If a covariant type appears as an output, the containing type is covariant. Producing a producer of Ts is like producing Ts. interface IReturnCovariant<out T> { IEnumerable<T> GetTs(); } If a contravariant type appears as an output, the containing type is contravariant. Produc...

With ASP.NET Core 1.0, the MVC and Web API framework have been merged into one framework called ASP.NET Core MVC. This is a good thing, since MVC and Web API share a lot of functionality, yet there always were subtle differences and code duplication. However, merging these two into framework one ...

LOOP AT itab INTO wa. ENDLOOP. FIELD-SYMBOLS <fs> LIKE LINE OF itab. LOOP AT itab ASSIGNING <fs>. ENDLOOP. LOOP AT itab ASSIGNING FIELD-SYMBOL(<fs>). ENDLOOP. LOOP AT itab REFERENCE INTO dref. ENDLOOP. LOOP AT itab TRANSPORTING NO FIELDS. ENDLOOP. Conditional L...

To make a custom pipe available application wide, During application bootstrap, extending PLATFORM_PIPES. import { bootstrap } from '@angular/platform-browser-dynamic'; import { provide, PLATFORM_PIPES } from '@angular/core'; import { AppComponent } from './app.component'; import { MyPipe }...

Detailed instructions on getting WSO2 set up or installed. Almost all the WSO2 Products can be started using the wso2server.sh/bat files that can be found in the <Product_Home>/bin folder of each product. When you run the sh/bat script it will star the particular WSO2 product with default set...

A topological ordering, or a topological sort, orders the vertices in a directed acyclic graph on a line, i.e. in a list, such that all directed edges go from left to right. Such an ordering cannot exist if the graph contains a directed cycle because there is no way that you can keep going right ...

Detailed instructions on getting magento2 set up or installed.

emptyList = [] singletonList = [0] -- = 0 : [] listOfNums = [1, 2, 3] -- = 1 : 2 : [3] listOfStrings = ["A", "B", "C"]

Sometimes you want to destructure key under a map which might not be present in the map, but you want a default value for the destructured value. You can do that this way: (def my-map {:a 3 :b 4}) (let [{a :a b :b :keys [c d] :or {a 1 c 2}} my-map] (println ...

Predicates that reason about instantiations are called meta-logical. Examples are: var/1 ground/1 integer/1 These predicates are outside the realm of pure monotonic logic programs, because they break properties like commutativity of conjunction. Other predicates that are meta-logical includ...

Predicates that reason about all solutions are extra-logical. These are for example: setof/3 findall/3 bagof/3

The MEDIAN function since Oracle 10g is an easy to use aggregation function: SELECT MEDIAN(SAL) FROM EMP It returns the median of the values Works on DATETIME values too. The result of MEDIAN is computed by first ordering the rows. Using N as the number of rows in the group, Oracle calcula...

Following code will release the lock. There will be no problem. Behind the scenes lock statement works as try finally lock(locker) { throw new Exception(); } More can be seen in the C# 5.0 Specification: A lock statement of the form lock (x) ... where x is an expression of a referenc...