Tutorial by Examples: r

Recovering from a lost commit

In case you have reverted back to a past commit and lost a newer commit you can recover the lost commit by running git reflog Then find your lost commit, and reset back to it by doing git reset HEAD --hard <sha1-of-commit>

Git • Recovering

Restore a deleted file after a commit

In case you have accidentally commited a delete on a file and later realized that you need it back. First find the commit id of the commit that deleted your file. git log --diff-filter=D --summary Will give you a sorted summary of commits which deleted files. Then proceed to restore the file b...

Git • Recovering

Restore file to a previous version

To restore a file to a previous version you can use reset. git reset <sha1-of-commit> <file-name> If you have already made local changes to the file (that you do not require!) you can also use the --hard option

Git • Recovering

Recover a deleted branch

To recover a deleted branch you need to find the commit which was the head of your deleted branch by running git reflog You can then recreate the branch by running git checkout -b <branch-name> <sha1-of-commit> You will not be able to recover deleted branches if git's garbage col...

Git • Recovering

Getting Started with CardView

CardView is a member of the Android Support Library, and provides a layout for cards. To add CardView to your project, add the following line to your build.gradle dependencies. compile 'com.android.support:cardview-v7:25.1.1' A number of the latest version may be found here In your layout you ...

Android • CardView

Joining an array of strings into a new one

var parts = new[] { "Foo", "Bar", "Fizz", "Buzz"}; var joined = string.Join(", ", parts); //joined = "Foo, Bar, Fizz, Buzz"

C# Language • Common String Operations

Hello World XML

SELECT 'Hello World' FOR XML PATH('example') <example>Hello World</example>

Microsoft SQL Server • FOR XML PATH

Specifying structure using XPath expressions

SELECT 'XPath example' AS 'head/title', 'This example demonstrates ' AS 'body/p', 'https://www.w3.org/TR/xpath/' AS 'body/p/a/@href', 'XPath expressions' AS 'body/p/a' FOR XML PATH('html') <html> <head> <title>XPath example</title> &...

Microsoft SQL Server • FOR XML PATH

Padding a string to a fixed length

string s = "Foo"; string paddedLeft = s.PadLeft(5); // paddedLeft = " Foo" (pads with spaces by default) string paddedRight = s.PadRight(6, '+'); // paddedRight = "Foo+++" string noPadded = s.PadLeft(2); // noPadded = "Foo" (original string...

C# Language • Common String Operations

Working with string messages

var wsHost = "ws://my-sites-url.com/path/to/echo-web-socket-handler"; var ws = new WebSocket(wsHost); var value = "an example message"; //onmessage : Event Listener - Triggered when we receive message form server ws.onmessage = function(message) { if (message === value...

JavaScript • WebSockets

Reducing values

5.1 The reduce() method applies a function against an accumulator and each value of the array (from left-to-right) to reduce it to a single value. Array Sum This method can be used to condense all values of an array into a single value: [1, 2, 3, 4].reduce(function(a, b) { return a + b; }); ...

JavaScript • Arrays

Class lambdas and capture of this

A lambda expression evaluated in a class' member function is implicitly a friend of that class: class Foo { private: int i; public: Foo(int val) : i(val) {} // definition of a member function void Test() { auto lamb = [](Foo &foo, int val) ...

C++ • Lambdas

Simulating variable-length lookbehind with \K

Some regex flavors (Perl, PCRE, Oniguruma, Boost) only support fixed-length lookbehinds, but offer the \K feature, which can be used to simulate variable-length lookbehind at the start of a pattern. Upon encountering a \K, the matched text up to this point is discarded, and only the text matching th...

Regular Expressions • Lookahead and Lookbehind

Newlines and control characters

A newline can be included in a single-string or double-quoted string. Note that backslash-newline does not result in a newline, the line break is ignored. newline1=' ' newline2=" " newline3=$'\n' empty=\ echo "Line${newline1}break" echo "Line${newline2}break" ...

Bash • Quoting

Double quotes for variable and command substitution

Variable substitutions should only be used inside double quotes. calculation='2 * 3' echo "$calculation" # prints 2 * 3 echo $calculation # prints 2, the list of files in the current directory, and 3 echo "$(($calculation))" # prints 6 Outside of doubl...

Bash • Quoting

Quoting literal text

All the examples in this paragraph print the line !"#$&'()*;<=>? @[\]^`{|}~ A backslash quotes the next character, i.e. the next character is interpreted literally. The one exception is a newline: backslash-newline expands to the empty string. echo \!\"\#\$\&\'\*\;\...

Bash • Quoting

Installing a TypeHandler

The above type handler can be installed into SqlMapper using the AddTypeHandler method. SqlMapper.AddTypeHandler<IHtmlString>(new IHtmlStringTypeHandler()); Type inference allows you to omit the generic type parameter: SqlMapper.AddTypeHandler(new IHtmlStringTypeHandler()); There's als...

Dapper.NET • Type Handlers

Bitwise OR

The | operator will perform a binary "or," where a bit is copied if it exists in either operand. That means: # 0 | 0 = 0 # 0 | 1 = 1 # 1 | 0 = 1 # 1 | 1 = 1 # 60 = 0b111100 # 30 = 0b011110 60 | 30 # Out: 62 # 62 = 0b111110 bin(60 | 30) # Out: 0b111110

Python Language • Bitwise Operators

Bitwise XOR (Exclusive OR)

The ^ operator will perform a binary XOR in which a binary 1 is copied if and only if it is the value of exactly one operand. Another way of stating this is that the result is 1 only if the operands are different. Examples include: # 0 ^ 0 = 0 # 0 ^ 1 = 1 # 1 ^ 0 = 1 # 1 ^ 1 = 0 # 60 = 0b1111...

Python Language • Bitwise Operators

Bitwise Right Shift

The >> operator will perform a bitwise "right shift," where the left operand's value is moved right by the number of bits given by the right operand. # 8 = 0b1000 8 >> 2 # Out: 2 # 2 = 0b10 bin(8 >> 2) # Out: 0b10 Performing a right bit shift of 1 is equivalent...

Python Language • Bitwise Operators