Tutorial by Examples: e

Python follows PEMDAS rule. PEMDAS stands for Parentheses, Exponents, Multiplication and Division, and Addition and Subtraction. Example: >>> a, b, c, d = 2, 3, 5, 7 >>> a ** (b + c) # parentheses 256 >>> a * b ** c # exponent: same as `a * (b ** c)` 7776 >>...

When performance is a concern, invoking a method via reflection (i.e. via the MethodInfo.Invoke method) is not ideal. However, it is relatively straightforward to obtain a more performant strongly-typed delegate using the Delegate.CreateDelegate function. The performance penalty for using reflecti...

In order to be able to use a class as the key in a map, all that is required of the key is that it be copiable and assignable. The ordering within the map is defined by the third argument to the template (and the argument to the constructor, if used). This defaults to std::less<KeyType>, w...

What we have is a list of credit cards and we'd like to calculate the premiums for all those cards that the credit card company has to pay out. The premiums themselves depend on the total number of credit cards, so that the company adjust them accordingly. We already have a function that calculate...

IMP is a C type referring to the implementation of a method, also known as an implementation pointer. It is a pointer to the start of a method implementation. Syntax: id (*IMP)(id, SEL, …) IMP is defined by: typedef id (*IMP)(id self,SEL _cmd,…); To access this IMP, the message “methodForSe...

When creating a timer, you can set the userInfo parameter to include information that you want to pass to the function you call with the timer. By taking a timer as a parameter in said function, you can access the userInfo property. NSDictionary *dictionary = @{ @&quo...

The HTTP message body can be compressed (since HTTP/1.1). Either by the server compresses the request and adds a Content-Encoding header, or by a proxy does and adds a Transfer-Encoding header. A client may send an Accept-Encoding request header to indicate which encodings it accepts. The most com...

Gson gson = new Gson(); //Create a Gson object MyType target = new MyType(); //This is the object you want to convert to JSON String json = gson.toJson(target); // serializes target to Json MyType target2 = gson.fromJson(json, MyType.class); // deserializes json into target2

Sometimes auto may behave not quite as was expected by a programmer. It type deduces the expression, even when type deduction is not the right thing to do. As an example, when proxy objects are used in the code: std::vector<bool> flags{true, true, false}; auto flag = flags[0]; flags.push_...

A _ character in a LIKE clause pattern matches a single character. Query SELECT username FROM users WHERE users LIKE 'admin_'; Result +----------+ | username | +----------+ | admin1 | | admin2 | | admin- | | adminA | +----------+

While using decorator syntax (with the @) is convenient, it also a bit concealing. You can use properties directly, without decorators. The following Python 3.x example shows this: class A: p = 1234 def getX (self): return self._x def setX (self, value): self._x =...

Multi-Editing allows the user to edit text at several locations simultaneously. Multi-Editing is disabled by default: it can be enabled (resp. disabled) in Preferences > Editing by checking (resp. unchecking) the related checkbox. To use Multi-Editing, the user can Ctrl Click on the differe...

Column Editing enables the user to edit text on several lines as a vertical square zone. This feature is enabled by default. There are 3 ways to select a zone to edit: Maintain Alt+Shift and use Up/Down/Left/Right to select the zone to edit with direction keys Maintain Alt+Shift and click on t...

The fact that the garbage collection will clean up does not mean that you should wait for the garbage collection cycle to clean up. In particular you should not wait for garbage collection to close file handles, database connections and open network connections. for example: In the following code...

Any String can be evaluated at runtime. class Example def self.foo :foo end end eval "Example.foo" #=> :foo

Ruby keeps track of local variables and self variable via an object called binding. We can get binding of a scope with calling Kernel#binding and evaluate string inside a binding via Binding#eval. b = proc do local_variable = :local binding end.call b.eval "local_variable" #=&gt...

The instance_eval method is available on all objects. It evaluates code in the context of the receiver: object = Object.new object.instance_eval do @variable = :value end object.instance_variable_get :@variable # => :value instance_eval sets self to object for the duration of the co...

Many languages feature a with statement that allows programmers to omit the receiver of method calls. with can be easily emulated in Ruby using instance_eval: def with(object, &block) object.instance_eval &block end The with method can be used to seamlessly execute methods on object...

It is possible to compress an HTTP response message body more than once. The encoding names should then be separated by a comma in the order in which they were applied. For example, if a message has been compressed via deflate and then gzip, the header should look like: Content-Encoding: deflate, g...

The client first sends a request with an Accept-Encoding header that indicates it supports gzip: GET / HTTP/1.1\r\n Host: www.google.com\r\n Accept-Encoding: gzip, deflate\r\n \r\n The server may then send a response with a compressed response body and a Content-Encoding header that specifies...