Tutorial by Examples: ed

let x = true match x with | true -> printfn "x is true" yields a warning C:\Program Files (x86)\Microsoft VS Code\Untitled-1(2,7): warning FS0025: Incomplete pattern matches on this expression. For example, the value 'false' may indicate a case not covered by the pattern(s). ...

Incorrect usage: In the following snippet, the last match will never be used: let x = 4 match x with | 1 -> printfn "x is 1" | _ -> printfn "x is anything that wasn't listed above" | 4 -> printfn "x is 4" prints x is anything that wasn't listed abov...

Jagged arrays are arrays that instead of primitive types, contain arrays (or other collections). It's like an array of arrays - each array element contains another array. They are similar to multidimensional arrays, but have a slight difference - as multidimensional arrays are limited to a fixed nu...

The MasterType directive assigns a class name to the Master property of a page, to make it strongly typed. The basic syntax of MasterType directive is: <%@ MasterType attribute="value"[attribute="value" ...] %>

The Page directive defines the attributes specific to the page file for the page parser and the compiler. The basic syntax of Page directive is: <%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" Trace="tr...

The OutputCache directive controls the output caching policies of a web page or a user control. The basic syntax of OutputCache directive is: <%@ OutputCache Duration="15" VaryByParam="None" %>

This example show how you can check if a service already exists (i.e., is installed on the machine) or not. This code requires only the lowest privileges necessary, so each process can perform the check, no matter what level of security it is running at. #define UNICODE #define _UNICODE #include ...

int x = INT_MAX + 1; // x can be anything -> Undefined behavior If during the evaluation of an expression, the result is not mathematically defined or not in the range of representable values for its type, the behavior is undefined. (C++11 Standard paragraph 5/4) This is one of the mo...

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....

<div class="navbar navbar-inverse navbar-fixed-top"> <div class="container"> <div class="navbar-header"> <!--- vvv Hamburger icon that gets shown when window reaches a certain scale vvv ---> <button type...

The case modifier causes the Scala compiler to automatically generate common boilerplate code for the class. Implementing this code manually is tedious and a source of errors. The following case class definition: case class Person(name: String, age: Int) ... will have the following code automati...

Predicates that produce side effects leave the realm of pure logic. These are for example: writeq/1 read/1 format/2 Side effects are phenomena that cannot be reasoned about within the program. For example, deletion of a file or output on the system terminal.

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...

Sometimes, we may open a file which we do not have permission to write in Vim without using sudo. Use this command to save a read-only file edited in Vim. :w !sudo tee > /dev/null % Which you could map to :w!! in your .vimrc: cmap w!! w !sudo tee > /dev/null % You will be presented a ...

There are many situation where you want to draw an image that is rotated, scaled, and translated. The rotation should occur around the center of the image. This is the quickest way to do so on the 2D canvas. These functions a well suited to 2D games where the expectation is to render a few hundred e...

pg_dump -Fc -f DATABASE.pgsql DATABASE The -Fc selects the "custom backup format" which gives you more power than raw SQL; see pg_restore for more details. If you want a vanilla SQL file, you can do this instead: pg_dump -f DATABASE.sql DATABASE or even pg_dump DATABASE > DATABA...

Angular 2.0.0-rc.4 In this example we'll create a "Hello World!" app with only one root component (AppComponent) for the sake of simplicity. Prerequisites: Node.js v5 or later npm v3 or later Note: You can check versions by running node -v and npm -v in the console/terminal. ...

Think about a situation where we need to callback a function with arguments. std::function used with std::bind gives a very powerful design construct as shown below. class A { public: std::function<void(int, const std::string&)> m_CbFunc = nullptr; void foo() { ...