Tutorial by Examples: v

Variables inside single quotes ' don't get expanded by POSIX compatible shells, so using a shell variable in a sed substitution requires the use of double quotes " instead of single quotes ': $ var="he" $ echo "hello" | sed "s/$var/XX/" XXllo $ var="he&q...

./mongo localhost:27017/mydb myjsfile.js Explanation: This operation executes the myjsfile.js script in a mongo shell that connects to the mydb database on the mongod instance accessible via the localhost interface on port 27017. localhost:27017 is not mandatory as this is the default port mongo...

When a column name matches a reserved keyword, standard SQL requires that you enclose it in double quotation marks: SELECT "ORDER", ID FROM ORDERS Note that it makes the column name case-sensitive. Some DBMSes have proprietary ways of quoting names. For example, SQL Serve...

asp:ListView introduced in ASP.NET WebForms framework 3.5 is the most flexible of all DataPresentation Controls in the framework. An example of Grouping using ListView (which will come handy as an image gallery) Objective: To display three images in a row using asp:ListView Markup <asp:ListVie...

Some convenience functions to manipulate data.frames are subset(), transform(), with() and within(). subset The subset() function allows you to subset a data.frame in a more convenient way (subset also works with other classes): subset(mtcars, subset = cyl == 6, select = c("mpg", "...

To catch a long click and use it you need to provide appropriate listener to button: View.OnLongClickListener listener = new View.OnLongClickListener() { public boolean onLongClick(View v) { Button clickedButton = (Button) v; String buttonText = clickedButton.getText().toStri...

Using environment variables is a widely used way to setting an app's config depending on it environment, as stated in The Twelve-Factor App. As configurations are likely to change between deployment environments, this is a very interesting way to modify the configuration without having to dig in th...

The things Array contains values of Any type. let things: [Any] = [1, "Hello", 2, true, false, "World", 3] We can extract values of a given type and create a new Array of that specific type. Let's say we want to extract all the Int(s) and put them into an Int Array in a safe ...

You can create a new hash with the keys or values modified, indeed you can also add or delete keys, using inject (AKA, reduce). For example to produce a hash with stringified keys and upper case values: fruit = { name: 'apple', color: 'green', shape: 'round' } # => {:name=>"apple",...

// The Option type can either contain Some value or None. fn find(value: i32, slice: &[i32]) -> Option<usize> { for (index, &element) in slice.iter().enumerate() { if element == value { // Return a value (wrapped in Some). return Some(index);...

Here is an example of a service that greets people by the given name, and keeps track of how many users it encountered. See usage below. %% greeter.erl %% Greets people and counts number of times it did so. -module(greeter). -behaviour(gen_server). %% Export API Functions -export([start_link/0...

If the variable contains a value of an immutable type (e.g. a string) then it is okay to assign a default value like this class Rectangle(object): def __init__(self, width, height, color='blue'): self.width = width self.height = height self.color = color d...

The virtualenvwrapper utility simplifies working with virtual environments and is especially useful if you are dealing with many virtual environments/projects. Instead of having to deal with the virtual environment directories yourself, virtualenvwrapper manages them for you, by storing all virtual...

When Fortran was originally developed memory was at a premium. Variables and procedure names could have a maximum of 6 characters, and variables were often implicitly typed. This means that the first letter of the variable name determines its type. variables beginning with i, j, ..., n are intege...

Python 3.x3.3 Use yield from if you want to yield all values from another iterable: def foob(x): yield from range(x * 2) yield from range(2) list(foob(5)) # [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1] This works with generators as well. def fibto(n): a, b = 1, 1 while True: ...

Given this setup code: var dict = new Dictionary<int, string>() { { 1, "First" }, { 2, "Second" }, { 3, "Third" } }; You may want to read the value for the entry with key 1. If key doesn't exist getting a value will throw KeyNotFoundException,...

The module cmath includes additional functions to use complex numbers. import cmath This module can calculate the phase of a complex number, in radians: z = 2+3j # A complex number cmath.phase(z) # 0.982793723247329 It allows the conversion between the cartesian (rectangular) and polar repr...

This a basic example aimed at new users. It does not focus on explaining the difference between char and cellstring. It might happen that you want to get rid of the ' in your strings, although you never added them. In fact, those are artifacts that the command window uses to distinguish between ...

Option Explicit Sub LoopAllSheets() Dim sht As Excel.Worksheet ' declare an array of type String without committing to maximum number of members Dim sht_Name() As String Dim i As Integer ' get the number of worksheets in Active Workbook , and put it as the maximum number of members in t...

Shift Use .shift to remove the first item of an array. For example: var array = [1, 2, 3, 4]; array.shift(); array results in: [2, 3, 4] Pop Further .pop is used to remove the last item from an array. For example: var array = [1, 2, 3]; array.pop(); array results in: [1, 2] Bot...