Tutorial by Examples: r

Accessing members of struct

In Swift, structures use a simple “dot syntax” to access their members. For example: struct DeliveryRange { var range: Double let center: Location } let storeLocation = Location(latitude: 44.9871, longitude: -93.2758) var pizzaRange = DeliveryRange(range: 200...

Swift Language • Structs

Installation or Setup

Installing OPAM OPAM is a package manager for OCaml. It builds and manages compiler versions and OCaml libraries for you easily. The easiest way to install OPAM on your operating system is to use a package manager for your system. e.g apt-get, yum or homebrew. Mac OSX Installation Instructions U...

OCaml • Getting started with OCaml

Get updates when a user's location changes

You can also receive regular updates of the user's location; for example, as they move around while using a mobile device. Location tracking over time can be very sensitive, so be sure to explain to the user ahead of time why you're requesting this permission and how you'll use the data. if (naviga...

JavaScript • Geolocation

Instantiating sun.misc.Unsafe via reflection

public static Unsafe getUnsafe() { try { Field unsafe = Unsafe.class.getDeclaredField("theUnsafe"); unsafe.setAccessible(true); return (Unsafe) unsafe.get(null); } catch (IllegalAccessException e) { // Handle } catch (IllegalArgumentExcept...

Java Language • sun.misc.Unsafe

Simple drop

Drop Table MyTable;

SQL • DROP Table

Check for existence before dropping

MySQL3.19 DROP TABLE IF EXISTS MyTable; PostgreSQL8.x DROP TABLE IF EXISTS MyTable; SQL Server2005 If Exists(Select * From Information_Schema.Tables Where Table_Schema = 'dbo' And Table_Name = 'MyTable') Drop Table dbo.MyTable SQLite3.0 DROP TABLE IF EXI...

SQL • DROP Table

Installation or Setup

Microsoft describes 3 ways of installing WinDbg: as part of the WDK (Windows Driver Kit) as part of the SDK (Software Development Kit) with the installer of the SDK and deselecting everything else but "Debugging Tools for Windows" To get the installer, visit Download the WDK, WinDb...

WinDbg • Getting started with WinDbg

Pitfall - Unnecessary use of Primitive Wrappers can lead to NullPointerExceptions

Sometimes, programmers who are new Java will use primitive types and wrappers interchangeably. This can lead to problems. Consider this example: public class MyRecord { public int a, b; public Integer c, d; } ... MyRecord record = new MyRecord(); record.a = 1; // OK ...

Java Language • Java Pitfalls - Nulls and NullPointerException

Multidex by using MultiDexApplication directly

Use this option if you don't need an Application subclass. This is the simplest option, but this way you can't provide your own Application subclass. If an Application subclass is needed, you will have to switch to one of the other options to do so. For this option, simply specify the fully-quali...

Android • Multidex and the Dex Method Limit

ReactJS component written in Typescript

You can use ReactJS's components easily in TypeScript. Just rename the 'jsx' file extension to 'tsx': //helloMessage.tsx: var HelloMessage = React.createClass({ render: function() { return <div>Hello {this.props.name}</div>; } }); ReactDOM.render(<HelloMessage name=&q...

TypeScript • Using Typescript with React (JS & native)

Block with

and



            
            
If the formatting (white space, new lines, indentation) of the code matters, use the pre element in combination with the code element:
&lt;pre&gt;
    &lt;code&gt;
    x = 42
    if x == 42:
        print &quot;x is …          … 42&quot;
    &lt;/code&gt;
&lt;/pre&gt;

You still have to esc...            

            
            
                
                    
                        HTML
                        •
                        Marking up computer code





    

        

            
            
                
                    Not matching a given string
                
            

            
            
To match something that does not contain a given string, one can use negative lookahead:
Regex syntax: (?!string-to-not-match)
Example:
//not matching &quot;popcorn&quot;
String regexString = &quot;^(?!popcorn).*$&quot;;
System.out.println(&quot;[popcorn] &quot; + (&quot;popcorn&quot;.matches(r...            

            
            
                
                    
                        Java Language
                        •
                        Regular Expressions
                        
                    
                    
                
            
        
    




    

        

            
            
                
                    Integration Tests
                
            

            
            
lib.rs:
pub fn to_test(output: bool) -&gt; bool {
    output
}

Each file in the tests/ folder is compiled as single crate.
tests/integration_test.rs
extern crate test_lib;
use test_lib::to_test;

#[test]
fn test_to_test(){
    assert_eq!(to_test(true), true);
}


            

            
            
                
                    
                        Rust
                        •
                        Tests
                        
                    
                    
                
            
        
    




    

        

            
            
                
                    char
                
            

            
            
A char is single letter stored inside a variable. It is built-in value type which takes two bytes of memory space. It represents System.Char data type found in mscorlib.dll which is implicitly referenced by every C# project when you create them.
There are multiple ways to do this.

char c = 'c';
...            

            
            
                
                    
                        C# Language
                        •
                        Keywords
                        
                    
                    
                
            
        
    




    

        

            
            
                
                    Column selection of a group
                
            

            
            
When you do a groupby you can select either a single column or a list of columns:
In [11]: df = pd.DataFrame([[1, 1, 2], [1, 2, 3], [2, 3, 4]], columns=[&quot;A&quot;, &quot;B&quot;, &quot;C&quot;])

In [12]: df
Out[12]:
   A  B  C
0  1  1  2
1  1  2  3
2  2  3  4

In [13]: g = df.groupby(...            

            
            
                
                    
                        pandas
                        •
                        Grouping Data
                        
                    
                    
                
            
        
    




    

        

            
            
                
                    Custom string interpolators
                
            

            
            
It is possible to define custom string interpolators in addition to the built-in ones.
my&quot;foo${bar}baz&quot;

Is expanded by the compiler to:
new scala.StringContext(&quot;foo&quot;, &quot;baz&quot;).my(bar)

scala.StringContext has no my method, therefore it can be provided by implicit c...            

            
            
                
                    
                        Scala Language
                        •
                        String Interpolation
                        
                    
                    
                
            
        
    




    

        

            
            
                
                    Databinding in Fragment
                
            

            
            
Data Model
public class Item {
    private String name;

    public String getName() {
        return name;
    }

    public void setName(String name){
        this.name = name;
    }

}

Layout XML
&lt;?xml version=&quot;1.0&quot; encoding=&quot;utf-8&quot;?&gt;
&lt;layout xmlns:an...            

            
            
                
                    
                        Android
                        •
                        Data Binding Library
                        
                    
                    
                
            
        
    




    

        

            
            
                
                    Parsing JSON property to enum with Gson
                
            

            
            
If you want to parse a String to enum with Gson:

{&quot;status&quot; : &quot;open&quot;}

public enum Status {
    @SerializedName(&quot;open&quot;)
    OPEN,
    @SerializedName(&quot;waiting&quot;)
    WAITING,
    @SerializedName(&quot;confirm&quot;)
    CONFIRM,
    @SerializedName(&...            

            
            
                
                    
                        Android
                        •
                        Gson
                        
                    
                    
                
            
        
    




    

        

            
            
                
                    Show Size of All Tables in Current Database 
                
            

            
            
SELECT
    s.name + '.' + t.NAME AS TableName,
    SUM(a.used_pages)*8 AS 'TableSizeKB'  --a page in SQL Server is 8kb
FROM sys.tables t
    JOIN sys.schemas s on t.schema_id = s.schema_id
    LEFT JOIN sys.indexes i ON t.OBJECT_ID = i.object_id
    LEFT JOIN sys.partitions p ON i.object_id = ...            

            
            
                
                    
                        Microsoft SQL Server
                        •
                        Retrieve information about the database
                        
                    
                    
                
            
        
    




    

        

            
            
                
                    Installation or Setup
                
            

            
            
Since JUnit is a Java library, all you have to do to install it is to add a few JAR files into the classpath of your Java project and you're ready to go.
You can download these two JAR files manually: junit.jar &amp; hamcrest-core.jar.
If you're using Maven, you can simply add in a dependency into...            

            
            
                
                    
                        junit
                        •
                        Getting started with junit