Tutorial by Examples: l

In Normal Mode, commands can be entered by direct key combinations (typing u to undo the last change, for example). These commands often have equivalents in 'ex' mode, accessed by typing a colon :, which drops you into a single-line buffer at the bottom of the Vim window. In 'ex' mode, after typing...

The Repeat command, executed with the dot or period key (.), is more useful than it first appears. Once learned, you will find yourself using it often. Command:Description.Repeat the last change10.Repeat the last change 10 times So then, for a very simple example, if you make a change to line 1 by...

C++11 A keyword denoting a null pointer constant. It can be converted to any pointer or pointer-to-member type, yielding a null pointer of the resulting type. Widget* p = new Widget(); delete p; p = nullptr; // set the pointer to null after deletion Note that nullptr is not itself a pointer. ...

For booleans, SQLite uses integers 0 and 1: sqlite> SELECT 2 + 2 = 4; 1 sqlite> SELECT 'a' = 'b'; 0 sqlite> SELECT typeof('a' = 'b'); integer > CREATE TABLE Users ( Name, IsAdmin ); > INSERT INTO Users VALUES ('root', 1); > INSERT INTO Users VALUES ('john', 0); > S...

SQLite uses dynamic typing and ignores declared column types: > CREATE TABLE Test ( Col1 INTEGER, Col2 VARCHAR(2), -- length is ignored, too Col3 BLOB, Col4, -- no type required Col5 FLUFFY BUNNIES -- use whatever you want ); > ...

You can define a method to accept an arbitrary number of keyword arguments using the double splat (**) operator: def say(**args) puts args end say foo: "1", bar: "2" # {:foo=>"1", :bar=>"2"} The arguments are captured in a Hash. You can manip...

By "class", we mean a type that was defined using the class or struct keyword (but not enum struct or enum class). Even an empty class still occupies at least one byte of storage; it will therefore consist purely of padding. This ensures that if p points to an object of an empty class...

This is very similar to using an Application subclass and overriding the attachBaseContext() method. However, using this method, you don't need to override attachBaseContext() as this is already done in the MultiDexApplication superclass. Extend MultiDexApplication instead of Application: package...

Automapper can be installed from nuget running the following command in Package Manager Console: Install-Package AutoMapper Then it can be included in different files within the project it has been installed to by using directives: using AutoMapper;

Unlike a parallel for-loop (parfor), which takes the iterations of a loop and distributes them among multiple threads, a single program, multiple data (spmd) statement takes a series of commands and distributes them to all the threads, so that each thread performs the command and stores the results....

Using Alternatives Many Linux distributions use the alternatives command for switching between different versions of a command. You can use this for switching between different versions of Java installed on a machine. In a command shell, set $JDK to the pathname of a newly installed JDK; e.g....

Given a DataFrame with MultiIndex columns # build an example DataFrame midx = pd.MultiIndex(levels=[['zero', 'one'], ['x','y']], labels=[[1,1,0,],[1,0,1,]]) df = pd.DataFrame(np.random.randn(2,3), columns=midx) In [2]: df Out[2]: one zero y x ...

Start with a standard DataFrame df = pd.DataFrame(np.random.randn(2,3), columns=['a','b','c']) In [91]: df Out[91]: a b c 0 -0.911752 -1.405419 -0.978419 1 0.603888 -1.187064 -0.035883 Now to change to MultiIndex, create a MultiIndex object and assign it to df....

MultiIndex can also be used to create DataFrames with multilevel columns. Just use the columns keyword in the DataFrame command. midx = pd.MultiIndex(levels=[['zero', 'one'], ['x','y']], labels=[[1,1,0,],[1,0,1,]]) df = pd.DataFrame(np.random.randn(6,4), columns=midx) In [86]: df Out[86]: ...

Dependencies can be added for specific product flavors in a similar fashion as build configurations. android { ... productFlavors { flavor1 { //... } flavor2 { //... } } } dependencies { flavor1Compile 'com.and...

There are many ways to print the classical "Hello world!" message in VHDL. The simplest of all is probably something like: -- File hello_world.vhd entity hello_world is end entity hello_world; architecture arc of hello_world is begin assert false report "Hello world!&quo...

es = Elasticsearch(hosts=hosts, sniff_on_start=True, sniff_on_connection_fail=True, sniffer_timeout=60, sniff_timeout=10, retry_on_timeout=True)

If you need to copy a database from one server to another, you have two options: Option 1: Store the dump file in the source server Copy the dump file to your destination server Load the dump file into your destination server On the source server: mysqldump [options] > dump.sql On th...

To remove all elements from a Map, use the .clear() method: map.clear(); Example: const map = new Map([[1, 2], [3, 4]]); console.log(map.size); // 2 map.clear(); console.log(map.size); // 0 console.log(map.get(1)); // undefined

To remove an element from a map use the .delete() method. map.delete(key); Example: const map = new Map([[1, 2], [3, 4]]); console.log(map.get(3)); // 4 map.delete(3); console.log(map.get(3)); // undefined This method returns true if the element existed and has been removed, otherwise fal...