Tutorial by Examples: u

Generate a table of dates using CTE

DECLARE @startdate CHAR(8), @numberDays TINYINT SET @startdate = '20160101' SET @numberDays = 10; WITH CTE_DatesTable AS ( SELECT CAST(@startdate as date) AS [date] UNION ALL SELECT DATEADD(dd, 1, [date]) FROM CTE_DatesTable WHERE DATEADD(dd, 1, [date]) <= DateAdd(DAY, @nu...

Using calc()

The calc() function is the part of a new syntax in CSS3 in which you can calculate (mathematically) what size/position your element occupies by using a variety of values like pixels, percentages, etc. Note:- Whenever you use this function, always take care of the space between two values calc(100% -...

When to use Currying

Currying is the technique of translating the evaluation of a function that takes multiple arguments into evaluating a sequence of functions, each with a single argument. This is normally useful when for example: different arguments of a function are calculated at different times. (Example 1) di...

PEP8 rules for Imports

Some recommended PEP8 style guidelines for imports: Imports should be on separate lines: from math import sqrt, ceil # Not recommended from math import sqrt # Recommended from math import ceil Order imports as follows at the top of the module: Standard libr...

Typical workflow of a neural network

The typical workflow of training and using neural networks, regardless of the library used, goes like this: Training Data Getting the training data: the X variable is the input, and the Y variable is the output. The simplest thing to do is to learn a logic gate, where X is a vector or two number...

Getting the Constants of an Enumeration

Giving this enumeration as Example: enum Compass { NORTH(0), EAST(90), SOUTH(180), WEST(270); private int degree; Compass(int deg){ degree = deg; } public int getDegree(){ return degree; } } In Java an enum class is like any other c...

Gauss's sum: 1 + 2 + 3 + ... + n

The sum 1 + 2 + 3 + ... + n Simplifies to n(n+1) / 2. Notice that this quantity is Θ(n2). This shortcut arises frequently in the analysis of algorithms like insertion sort or selection sort. Numbers of the form n(n+1)/2 are called the triangular numbers.

Sums of Powers of Two: 1 + 2 + 4 + 8 + 16 + ...

The sum 20 + 21 + 22 + ... + 2n-1 simplifies to 2n - 1. This explains why the maximum value that can be stored in an unsigned 32-bit integer is 232 - 1.

Sum of a geometric series: r^0 + r^1 + r^2 + ...

The sum of the geometric series r0 + r1 + r2 + ... + rn-1 In the case where r ≠ 1, simplifies to (rn - 1) / (r - 1). If r < 1, this sum is bounded from above by 1 / (1 - r). If r = 1, this sum is rn.

Adding a spinner to your activity

In /res/values/strings.xml: <string-array name="spinner_options"> <item>Option 1</item> <item>Option 2</item> <item>Option 3</item> </string-array> In layout XML: <Spinner android:id="@+id/spinnerName" ...

Basics of texturing

A texture is a form of data storage that allows convenient access not just to particular data entries, but also to sample points mixing (interpolating) multiple entries together. In OpenGL textures can be used for many things, but most commonly it's mapping an image to a polygon (for example a tria...

Update an existing model

$user = User::find(1); $user->name = 'abc'; $user->save(); You can also update multiple attributes at once using update, which does not require using save afterwards: $user = User::find(1); $user->update(['name' => 'abc', 'location' => 'xyz']); You can also update a model(s)...

Throw 404 if entity not found

If you want to automatically throw an exception when searching for a record that isn't found on a modal, you can use either Vehicle::findOrFail(1); or Vehicle::where('make', 'ford')->firstOrFail(); If a record with the primary key of 1 is not found, a ModelNotFoundException is thrown. W...

A View Bound to Existing HTML

Assuming this HTML in the page: <body> <div id="myPage"> </div> </body> A view can be bound to it with: var MyPageView = Backbone.View.extend( { "el": "#myPage", "template": _.template( "<p>This is m...

View's initialize function

initialize is called by Backbone right after a View is constructed. Optional parameters The initialize function receives any arguments passed to the view's constructor. Commonly, the options hash that is used to pass the view's default options: ['model', 'collection', 'el', 'id', 'attributes', 'c...

Gem installation from github/filesystem

You can install a gem from github or filesystem. If the gem has been checked out from git or somehow already on the file system, you could install it using gem install --local path_to_gem/filename.gem Installing gem from github. Download the sources from github mkdir newgem cd newgem git clon...

Defining Variadic Functions

A Clojure function can be defined to take an arbitrary number of arguments, using the symbol & in its argument list. All remaining arguments are collected as a sequence. (defn sum [& args] (apply + args)) (defn sum-and-multiply [x & args] (* x (apply + args))) Calling: =&gt...

Single & Multiple line comments

Comments are programmer-readable annotations that are ignored at runtime. Their purpose is to make source code easier to understand. Single line comments The # character is used to add single line comments. #!/usr/bin/ruby -w # This is a single line comment. puts "Hello World!" Whe...

Use CStr to convert a numeric type to a string

Const zipCode As Long = 10012 Dim zipCodeText As String 'Convert the zipCode number to a string of digit characters zipCodeText = CStr(zipCode) 'zipCodeText = "10012"

Use Format to convert and format a numeric type as a string

Const zipCode As long = 10012 Dim zeroPaddedNumber As String zeroPaddedZipCode = Format(zipCode, "00000000") 'zeroPaddedNumber = "00010012"

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