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While the math.sqrt function is provided for the specific case of square roots, it's often convenient to use the exponentiation operator (**) with fractional exponents to perform nth-root operations, like cube roots. The inverse of an exponentiation is exponentiation by the exponent's reciprocal. S...

To access entities declared in a module from another program unit (module, procedure or program), the module must be used with the use statement. module shared_data implicit none integer :: iarray(4) = [1, 2, 3, 4] real :: rarray(4) = [1., 2., 3., 4.] end module program test !...

At some point in your use of Django, you may find yourself wanting to interact with tables which have already been created, or with database views. In these cases, you would not want Django to manage the tables through its migrations. To set this up, you need to add only one variable to your model's...

Literal format strings were introduced in PEP 498 (Python3.6 and upwards), allowing you to prepend f to the beginning of a string literal to effectively apply .format to it with all variables in the current scope. >>> foo = 'bar' >>> f'Foo is {foo}' 'Foo is bar' This works wi...

The background-position property is used to specify the starting position for a background image or gradient .myClass { background-image: url('path/to/image.jpg'); background-position: 50% 50%; } The position is set using an X and Y co-ordinate and be set using any of the units used withi...

This assumes that you have read the documentation about starting a new Django project. Let us assume that the main app in your project is named td (short for test driven). To create your first test, create a file named test_view.py and copy paste the following content into it. from django.test impo...

Detailed instructions on getting couchbase set up or installed.

Getting the Constructor Object You can obtain Constructor class from the Class object like this: Class myClass = ... // get a class object Constructor[] constructors = myClass.getConstructors(); Where the constructors variable will have one Constructor instance for each public constructor decl...

Many C interfaces such as SDL2 have their own deletion functions. This means that you cannot use smart pointers directly: std::unique_ptr<SDL_Surface> a; // won't work, UNSAFE! Instead, you need to define your own deleter. The examples here use the SDL_Surface structure which should be fre...

To demystify Template Haskell, suppose you have data Example a = Example { _foo :: Int, _bar :: a } then makeLenses 'Example produces (more or less) foo :: Lens' (Example a) Int bar :: Lens (Example a) (Example b) a b There's nothing particularly magical going on, though. You can write ...

A Lens' s a means that you can always find an a within any s. A Prism' s a means that you can sometimes find that s actually just is a but sometimes it's something else. To be more clear, we have _1 :: Lens' (a, b) a because any tuple always has a first element. We have _Just :: Prism' (Maybe a) a...

A Traversal' s a shows that s has 0-to-many as inside of it. toListOf :: Traversal' s a -> (s -> [a]) Any type t which is Traversable automatically has that traverse :: Traversal (t a) a. We can use a Traversal to set or map over all of these a values > set traverse 1 [1..10] [1,1,1,...

main.go: package main import ( "fmt" ) func main() { fmt.Println(Sum(4,5)) } func Sum(a, b int) int { return a + b } main_test.go: package main import ( "testing" ) // Test methods start with `Test` func TestSum(t *testing.T) { go...

If you want to measure benchmarks add a testing method like this: sum.go: package sum // Sum calculates the sum of two integers func Sum(a, b int) int { return a + b } sum_test.go: package sum import "testing" func BenchmarkSum(b *testing.B) { for i := 0; i < ...

This type of testing is popular technique for testing with predefined input and output values. Create a file called main.go with content: package main import ( "fmt" ) func main() { fmt.Println(Sum(4, 5)) } func Sum(a, b int) int { return a + b } After you r...

This type of tests make sure that your code compiles properly and will appear in the generated documentation for your project. In addition to that, the example tests can assert that your test produces proper output. sum.go: package sum // Sum calculates the sum of two integers func Sum(a, b in...

You can use Optional Chaining in order to call a method, access a property or subscript an optional. This is done by placing a ? between the given optional variable and the given member (method, property or subscript). struct Foo { func doSomething() { print("Hello World!") ...

SelectorDescription*Universal selector (all elements)divTag selector (all <div> elements).blueClass selector (all elements with class blue).blue.redAll elements with class blue and red (a type of Compound selector)#headlineID selector (the element with "id" attribute set to headline)...

Here is a simple model that we will use to run a few test queries: class MyModel(models.Model): name = models.CharField(max_length=10) model_num = models.IntegerField() flag = models.NullBooleanField(default=False) Get a single model object where the id/pk is 4: (If there are no...

Context processor to determine the template based on group membership(or any query/logic). This allows our public/regular users to get one template and our special group to get a different one. myapp/context_processors.py def template_selection(request): site_template = 'template_public.html...