Tutorial by Examples: l

The Symbol.for method allows you to register and look up global symbols by name. The first time it is called with a given key, it creates a new symbol and adds it to the registry. let a = Symbol.for('A'); The next time you call Symbol.for('A'), the same symbol will be returned instead of a new o...

For more complex applications, flat execution profiles may be difficult to follow. This is why many profiling tools also generate some form of annotated callgraph information. gperf2dot converts text output from many profilers (Linux perf, callgrind, oprofile etc.) into a callgraph diagram. You can...

Google Perf Tools also provides a CPU profiler, with a slightly friendlier interface. To use it: Install Google Perf Tools Compile your code as usual Add the libprofiler profiler library to your library load path at runtime Use pprof to generate a flat execution profile, or a callgraph diagram...

The | can be used to have a single case statement match against multiple inputs to yield the same result: def f(str: String): String = str match { case "foo" | "bar" => "Matched!" case _ => "No match." } f("foo") // res0: String = M...

Given the following List of tuples: val pastries = List(("Chocolate Cupcake", 2.50), ("Vanilla Cupcake", 2.25), ("Plain Muffin", 3.25)) Pattern matching can be used to handle each element differently: pastries foreach { pa...

Bootstrapping Magento by calling: require_once 'app/Mage.php'; Mage::app(); // Your code This is the simplest way but not really the Magento way because we're not using class that extends Mage_Shell_Abstract - the class which when extended provides us with tools to parse command line arguments...

Magento way File resides in shell/custom.php <?php require_once' abstract.php'; class Stackoverflow_Shell_Custom extends Mage_Shell_Abstract { protected $_argname = array(); public function __construct() { parent::__construct(); // Time limit to infinity ...

The std::nth_element algorithm takes three iterators: an iterator to the beginning, nth position, and end. Once the function returns, the nth element (by order) will be the nth smallest element. (The function has more elaborate overloads, e.g., some taking comparison functors; see the above link for...

.exr -1 gives you details about the last exception thrown. !analyze -v usually does a good job as well. For .NET, the command !pe of the SOS extension shows details about the .NET exception that was thrown.

Hosted XSLT 2.0 Setup To run XSLT 2.0 in the browser, use one of the following XSLT 2.0 as a service hosts: XSLT Fiddle W3C XSLT Servlet Online XSLT Test Tool

Print the path to the active developer directory (selected Xcode) xcode-select -p Select a different version of Xcode, e.g. Beta sudo xcode-select -s /Applications/Xcode-beta.app Reset to the default version of Xcode sudo xcode-select -r This is equivalent to running sudo xcode-select -s /Appl...

Ref returns and ref locals are useful for manipulating and returning references to blocks of memory instead of copying memory without resorting to unsafe pointers. Ref Return public static ref TValue Choose<TValue>( Func<bool> condition, ref TValue left, ref TValue right) { ...

The keyword partial can be used during type definition of class, struct, or interface to allow the type definition to be split into several files. This is useful to incorporate new features in auto generated code. File1.cs namespace A { public partial class Test { public string...

array_flip function will exchange all keys with its elements. $colors = array( 'one' => 'red', 'two' => 'blue', 'three' => 'yellow', ); array_flip($colors); //will output array( 'red' => 'one', 'blue' => 'two', 'yellow' => 'three' )

When pasting text through a terminal emulator, the auto-indent feature may destroy the indentation of the pasted text. For example: function () { echo 'foo' echo 'bar' echo 'baz' } will be pasted as: function () { echo 'foo' echo 'bar' echo 'baz' ...

When static_cast is used to convert T D::* to T B::*, the member pointed to must belong to a class that is a base class or derived class of B. Otherwise the behavior is undefined. See Derived to base conversion for pointers to members

The following uses of pointer arithmetic cause undefined behavior: Addition or subtraction of an integer, if the result does not belong to the same array object as the pointer operand. (Here, the element one past the end is considered to still belong to the array.) int a[10]; int* p1 = &a...

For the built-in shift operator, the right operand must be nonnegative and strictly less than the bit width of the promoted left operand. Otherwise, the behavior is undefined. const int a = 42; const int b = a << -1; // UB const int c = a << 0; // ok const int d = a << 32; // ...

In this example, a destructor is explicitly invoked for an object that will later be automatically destroyed. struct S { ~S() { std::cout << "destroying S\n"; } }; int main() { S s; s.~S(); } // UB: s destroyed a second time here A similar issue occurs when a st...

Example from the Standard, [temp.inst]/17: template<class T> class X { X<T>* p; // OK X<T*> a; // implicit generation of X<T> requires // the implicit instantiation of X<T*> which requires // the implicit instantiation of X<T**&...