Tutorial by Examples: u

Dim aList as New List(Of String) aList.Add("one") aList.Add("two") aList.Add("three") For Each str As String in aList System.Console.WriteLine(str) Next Produces the following output: one two three Another option, would be to loop through using the ...

Microsoft Access is an Application Generator for developing databases and data-driven applications, primarily for local use. Microsoft Access consists of two main elements: A Relational Database Management System (RDBMS) that combines the Microsoft Jet Database Engine (Access 2003 and earler) or ...

Related to Monads are F# computation expressions (CE). A programmer typically implements a CE to provide an alternative approach to chaining Monads, ie instead of this: let v = m >>= fun x -> n >>= fun y -> return_ (x, y) You can write this: let v = ce { let! x = m ...

Most programming languages, including F#, evaluate computations immediately in accord with a model called Strict Evaluation. However, in Lazy Evaluation, computations are not evaluated until they are needed. F# allows us to use lazy evaluation through both the lazy keyword and sequences. // define ...

F#, like most programming languages, uses Strict Evaluation by default. In Strict Evaluation, computations are executed immediately. In contrast, Lazy Evaluation, defers execution of computations until their results are needed. Moreover, the results of a computation under Lazy Evaluation are cached,...

In Emacs, file has the same meaning as in the operating system, and is used for permanent storage of data. A buffer is the internal representation of a file being edited. Files can be read into buffers using C-x C-f, and buffers can be written to files using C-x C-s (save file at its current locatio...

Emacs's user interface uses terms that were coined early and can be unsettling to users used to a more modern terminology. Frame In Emacs, what is otherwise called a window (the area of the display used by a program) is called a frame. Emacs starts using one frame, though additional frames may b...

Sometimes it is desirable to evaluate a nullable expression in an if-else fashion. The elvis operator, ?:, can be used in Kotlin for such a situation. For instance: val value: String = data?.first() ?: "Nothing here." The expression above returns "Nothing here" if data?.firs...

Attribute values can appear in simple or double quotes. The appropriate character must be escaped. <?xml version="1.0"?> <document quot-attribute="This is a "double quote" and this one is 'simple'" apos-attribute='This is a 'simple quot...

Examples of numeric fields are given: AutoField An auto-incrementing integer generally used for primary keys. from django.db import models class MyModel(models.Model): pk = models.AutoField() Each model gets a primary key field (called id) by default. Therefore, it is not necessary t...

Detailed instructions on getting xquery set up or installed.

In real world, connection and server delays could occur, to simulate delays in development environment Meteor._sleepForMs(ms); could be used Meteor.publish('USER_DATA', function() { Meteor._sleepForMs(3000); // Simulate 3 seconds delay return Meteor.users.find({}); });

select '123' * 2; To make the multiplication with 2 MySQL automatically converts the string 123 into a number. Return value: 246 The conversion to a number starts from left to right. If the conversion is not possible the result is 0 select '123ABC' * 2 Return value: 246 select 'A...

Suppose we want to get all product categories with total sales greater than 20. Here is a query without Common Table Expressions: SELECT category.description, sum(product.price) as total_sales FROM sale LEFT JOIN product on sale.product_id = product.id LEFT JOIN category on product.category_id ...

SELECT x, ... FROM ( SELECT y, ... FROM ... ) AS a JOIN tbl ON tbl.x = a.y WHERE ... This will evaluate the subquery into a temp table, then JOIN that to tbl. Prior to 5.6, there could not be an index on the temp table. So, this was potentially very inefficient: SELECT ... ...

R is full of functions, it is after all a functional programming language, but sometimes the precise function you need isn't provided in the Base resources. You could conceivably install a package containing the function, but maybe your requirements are just so specific that no pre-made function fit...

An anonymous function is, as the name implies, not assigned a name. This can be useful when the function is a part of a larger operation, but in itself does not take much place. One frequent use-case for anonymous functions is within the *apply family of Base functions. Calculate the root mean squ...

TRUNCATE tableName; This will delete all the data and reset AUTO_INCREMENT index. It's much faster than DELETE FROM tableName on a huge dataset. It can be very useful during development/testing. When you truncate a table SQL server doesn't delete the data, it drops the table and recreates it, th...

The following will echo each line in the file C:\scripts\testFile.txt. Blank lines will not be processed. for /F "tokens=*" %%A in (C:\scripts\testFile.txt) do ( echo %%A rem do other stuff here ) More advanced example shows, how derived in FOR loop from a restricted files set...

From command line: cpan -l From a Perl script: use ExtUtils::Installed; my $inst = ExtUtils::Installed->new(); my @modules = $inst->modules();