Tutorial by Examples: st

When a user subscribes to a channel, you may want to set state for that newly subscribed user. While there is a subscribe with state API, there are some scenarios where this is not the most optimal/reliable technique (like during a disconnect/reconnect situation - the state will be lost and not rein...

var='0123456789abcdef' # Define a zero-based offset $ printf '%s\n' "${var:3}" 3456789abcdef # Offset and length of substring $ printf '%s\n' "${var:3:4}" 3456 4.2 # Negative length counts from the end of the string $ printf '%s\n' "${var:3:-5}" 3456789a...

cat < file.txt Output is same as cat file.txt, but it reads the contents of the file from standard input instead of directly from the file. printf "first line\nSecond line\n" | cat -n The echo command before | outputs two lines. The cat command acts on the output to add line num...

One of the most common tasks is retrieving an existing element from the DOM to manipulate. Most commonly these methods are executed on document, because it is the root node, but all these methods work on any HTML element in the tree. They will only return children from the node it is executed on. R...

The class template std::shared_ptr defines a shared pointer that is able to share ownership of an object with other shared pointers. This contrasts to std::unique_ptr which represents exclusive ownership. The sharing behavior is implemented through a technique known as reference counting, where the...

Instances of std::weak_ptr can point to objects owned by instances of std::shared_ptr while only becoming temporary owners themselves. This means that weak pointers do not alter the object's reference count and therefore do not prevent an object's deletion if all of the object's shared pointers are ...

A std::vector can be initialized in several ways while declaring it: C++11 std::vector<int> v{ 1, 2, 3 }; // v becomes {1, 2, 3} // Different from std::vector<int> v(3, 6) std::vector<int> v{ 3, 6 }; // v becomes {3, 6} // Different from std::vector<int> v{3, ...

You can iterate over a std::vector in several ways. For each of the following sections, v is defined as follows: std::vector<int> v; Iterating in the Forward Direction C++11 // Range based for for(const auto& value: v) { std::cout << value << "\n"; } /...

There are several ways to use a std::vector as a C array (for example, for compatibility with C libraries). This is possible because the elements in a vector are stored contiguously. C++11 std::vector<int> v{ 1, 2, 3 }; int* p = v.data(); In contrast to solutions based on previous C++ st...

To mark text as inserted, use the <ins> tag: <ins>New Text</ins> To mark text as deleted, use the <del> tag: <del>Deleted Text</del> To strike through text, use the <s> tag: <s>Struck-through text here</s>

Standard Collections Java Collections framework A simple way to construct a List from individual data values is to use java.utils.Arrays method Arrays.asList: List<String> data = Arrays.asList("ab", "bc", "cd", "ab", "bc", "cd"); ...

If you are using the PASSWORD_DEFAULT method to let the system choose the best algorithm to hash your passwords with, as the default increases in strength you may wish to rehash old passwords as users log in <?php // first determine if a supplied password is valid if (password_verify($plaintex...

password_verify() is the built-in function provided (as of PHP 5.5) to verify the validity of a password against a known hash. <?php if (password_verify($plaintextPassword, $hashedPassword)) { echo 'Valid Password'; } else { echo 'Invalid Password.'; } ?> All supported hashi...

Unlike classes, which are passed by reference, structures are passed through copying: first = "Hello" second = first first += " World!" // first == "Hello World!" // second == "Hello" String is a structure, therefore it's copied on assignment. Structu...

Add the following target in your build.xml <!-- Bootstrap ivy --> <target name="ivy.bootstrap" description="Download Apache Ivy"> <!-- Define the version to use --> <property name="ivy.version">2.4.0</property> <!-- ...

Lazy stored properties have values that are not calculated until first accessed. This is useful for memory saving when the variable's calculation is computationally expensive. You declare a lazy property with lazy: lazy var veryExpensiveVariable = expensiveMethod() Often it is assigned to a retu...

Mathematical operations on values other than numbers return NaN. "a" + 1 "b" * 3 "cde" - "e" [1, 2, 3] * 2 An exception: Single-number arrays. [2] * [3] // Returns 6 Also, remember that the + operator concatenates strings. "a" + "b&...

Generally, Math functions that are given non-numeric arguments will return NaN. Math.floor("a") The square root of a negative number returns NaN, because Math.sqrt does not support imaginary or complex numbers. Math.sqrt(-1)

window.isNaN() The global function isNaN() can be used to check if a certain value or expression evaluates to NaN. This function (in short) first checks if the value is a number, if not tries to convert it (*), and then checks if the resulting value is NaN. For this reason, this testing method may ...

Following ways can be used for joining lists without modifying source list(s). First approach. Has more lines but easy to understand List<String> newList = new ArrayList<String>(); newList.addAll(listOne); newList.addAll(listTwo); Second approach. Has one less line but less readab...