Tutorial by Examples: le

The and-operator (&&) and the or-operator (||) employ short-circuiting to prevent unnecessary work if the outcome of the operation does not change with the extra work. In x && y, y will not be evaluated if x evaluates to false, because the whole expression is guaranteed to be false....

Dates don't exist in isolation. It is common that you will need to find the amount of time between dates or determine what the date will be tomorrow. This can be accomplished using timedelta objects import datetime today = datetime.date.today() print('Today:', today) yesterday = today - date...

C++11 The type std::tuple can bundle any number of values, potentially including values of different types, into a single return object: std::tuple<int, int, int, int> foo(int a, int b) { // or auto (C++14) return std::make_tuple(a + b, a - b, a * b, a / b); } In C++17, a braced init...

var fs = require('fs'); // Save the string "Hello world!" in a file called "hello.txt" in // the directory "/tmp" using the default encoding (utf8). // This operation will be completed in background and the callback // will be called when it is either done or fail...

Use the filesystem module for all file operations: const fs = require('fs'); With Encoding In this example, read hello.txt from the directory /tmp. This operation will be completed in the background and the callback occurs on completion or failure: fs.readFile('/tmp/hello.txt', { encoding: '...

project/jni/main.c #include <stdio.h> #include <unistd.h> int main(void) { printf("Hello world!\n"); return 0; } project/jni/Android.mk LOCAL_PATH := $(call my-dir) include $(CLEAR_VARS) LOCAL_MODULE := hello_world LOCAL_SRC_FILES := main.c include $(BU...

In ECMAScript 6, when using the module syntax (import/export), each file becomes its own module with a private namespace. Top-level functions and variables do not pollute the global namespace. To expose functions, classes, and variables for other modules to import, you can use the export keyword. /...

Given that the module from the Defining a Module section exists in the file test.js, you can import from that module and use its exported members: import {doSomething, MyClass, PI} from './test' doSomething() const mine = new MyClass() mine.test() console.log(PI) The somethingPrivate()...

Opening a file is done in the same way for all 3 file streams (ifstream, ofstream, and fstream). You can open the file directly in the constructor: std::ifstream ifs("foo.txt"); // ifstream: Opens file "foo.txt" for reading only. std::ofstream ofs("foo.txt"); // ...

There are several ways to read data from a file. If you know how the data is formatted, you can use the stream extraction operator (>>). Let's assume you have a file named foo.txt which contains the following data: John Doe 25 4 6 1987 Jane Doe 15 5 24 1976 Then you can use the following...

There are several ways to write to a file. The easiest way is to use an output file stream (ofstream) together with the stream insertion operator (<<): std::ofstream os("foo.txt"); if(os.is_open()){ os << "Hello World!"; } Instead of <<, you can also ...

Explicitly closing a file is rarely necessary in C++, as a file stream will automatically close its associated file in its destructor. However, you should try to limit the lifetime of a file stream object, so that it does not keep the file handle open longer than necessary. For example, this can be ...

In addition to importing named members from a module or a module's default export, you can also import all members into a namespace binding. import * as test from './test' test.doSomething() All exported members are now available on the test variable. Non-exported members are not available, j...

Let's say you've got a list of restaurants -- maybe you read it from a file. You care about the unique restaurants in the list. The best way to get the unique elements from a list is to turn it into a set: restaurants = ["McDonald's", "Burger King", "McDonald's", &qu...

Counter is a dict sub class that allows you to easily count objects. It has utility methods for working with the frequencies of the objects that you are counting. import collections counts = collections.Counter([1,2,3]) the above code creates an object, counts, which has the frequencies of all ...

collections.defaultdict(default_factory) returns a subclass of dict that has a default value for missing keys. The argument should be a function that returns the default value when called with no arguments. If there is nothing passed, it defaults to None. >>> state_capitals = collections.d...

$ git branch -d dev Deletes the branch named dev if its changes are merged with another branch and will not be lost. If the dev branch does contain changes that have not yet been merged that would be lost, git branch -d will fail: $ git branch -d dev error: The branch 'dev' is not fully merged...

To remove an element inside an array, e.g. the element with the index 1. $fruit = array("bananas", "apples", "peaches"); unset($fruit[1]); This will remove the apples from the list, but notice that unset does not change the indexes of the remaining elements. So $fr...

Boolean is a type, having two values, denoted as true or false. This code sets the value of $foo as true and $bar as false: $foo = true; $bar = false; true and false are not case sensitive, so TRUE and FALSE can be used as well, even FaLsE is possible. Using lower case is most common and recom...

# Length of a string $ var='12345' $ echo "${#var}" 5 Note that it's the length in number of characters which is not necessarily the same as the number of bytes (like in UTF-8 where most characters are encoded in more than one byte), nor the number of glyphs/graphemes (some of which ...