Tutorial by Examples: com

While composer provides a system to manage dependencies for PHP projects (e.g. from Packagist), it can also notably serve as an autoloader, specifying where to look for specific namespaces or include generic function files. It starts with the composer.json file: { // ... "autoload&q...

While many people think that ^ means the start of a string, it actually means start of a line. For an actual start of string anchor use, \A. The string hello\nworld (or more clearly) hello world Would be matched by the regular expressions ^h, ^w and \Ah but not by \Aw

PowerShell comparison operators are comprised of a leading dash (-) followed by a name (eq for equal, gt for greater than, etc...). Names can be preceded by special characters to modify the behavior of the operator: i # Case-Insensitive Explicit (-ieq) c # Case-Sensitive Explicit (-ceq) Case-I...

// Execute a command a capture standard out. exec.Command creates the command // and then the chained Output method gets standard out. Use CombinedOutput() // if you want both standard out and standerr output out, err := exec.Command("echo", "foo").Output() if err != nil { ...

cmd := exec.Command("sleep", "5") // Does not wait for command to complete before returning err := cmd.Start() if err != nil { log.Fatal(err) } // Wait for cmd to Return err = cmd.Wait() log.Printf("Command finished with error: %v", err)

A popular form of data analysis is split-apply-combine, in which you split your data into groups, apply some sort of processing on each group, and then combine the results. Let's consider a data analysis where we want to obtain the two cars with the best miles per gallon (mpg) for each cylinder cou...

The filter or map functions should often be replaced by list comprehensions. Guido Van Rossum describes this well in an open letter in 2005: filter(P, S) is almost always written clearer as [x for x in S if P(x)], and this has the huge advantage that the most common usages involve predicates tha...

The module cmath includes additional functions to use complex numbers. import cmath This module can calculate the phase of a complex number, in radians: z = 2+3j # A complex number cmath.phase(z) # 0.982793723247329 It allows the conversion between the cartesian (rectangular) and polar repr...

Python has built-in support for complex arithmetic. The imaginary unit is denoted by j: z = 2+3j # A complex number w = 1-7j # Another complex number Complex numbers can be summed, subtracted, multiplied, divided and exponentiated: z + w # (3-4j) z - w # (1+10j) z * w # (23-11j) z / w # (...

This a basic example aimed at new users. It does not focus on explaining the difference between char and cellstring. It might happen that you want to get rid of the ' in your strings, although you never added them. In fact, those are artifacts that the command window uses to distinguish between ...

Key Value Coding is integrated into NSObject using NSKeyValueCoding protocol. What this means? It means that any id object is capable of calling valueForKey method and its various variants like valueForKeyPath etc. ' It also means that any id object can invoke setValue method and its various vari...

Long vectors with long runs of the same value can be significantly compressed by storing them in their run-length encoding (the value of each run and the number of times that value is repeated). As an example, consider a vector of length 10 million with a huge number of 1's and only a small number o...

A React component can be defined as an ES6 class that extends the base React.Component class. In its minimal form, a component must define a render method that specifies how the component renders to the DOM. The render method returns React nodes, which can be defined using JSX syntax as HTML-like ta...

The for clause of a list comprehension can specify more than one variable: [x + y for x, y in [(1, 2), (3, 4), (5, 6)]] # Out: [3, 7, 11] [x + y for x, y in zip([1, 3, 5], [2, 4, 6])] # Out: [3, 7, 11] This is just like regular for loops: for x, y in [(1,2), (3,4), (5,6)]: print(x+y) ...

Two std::strings can be compared lexicographically using the operators ==, !=, <, <=, >, and >=: std::string str1 = "Foo"; std::string str2 = "Bar"; assert(!(str1 < str2)); assert(str > str2); assert(!(str1 <= str2)); assert(str1 >= str2); assert...

Given the following HTML file: index.html <!DOCTYPE html> <html> <head> <meta charset="utf-8" /> <title>React Tutorial</title> <script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.2.1/react.js"></script>...

Composer tracks which versions of packages you have installed in a file called composer.lock, which is intended to be committed to version control, so that when the project is cloned in the future, simply running composer install will download and install all the project's dependencies. Composer de...

A lot of the power of ReactJS is its ability to allow nesting of components. Take the following two components: var React = require('react'); var createReactClass = require('create-react-class'); var CommentList = reactCreateClass({ render: function() { return ( <div className...

Given the following history, imagine you make a change that you want to squash into the commit bbb2222 A second commit: $ git log --oneline --decorate ccc3333 (HEAD -> master) A third commit bbb2222 A second commit aaa1111 A first commit 9999999 Initial commit Once you've made your change...

git cherry-pick <commit-A>..<commit-B> will place every commit after A and up to and including B on top of the currently checked-out branch. git cherry-pick <commit-A>^..<commit-B> will place commit A and every commit up to and including B on top of the currently checked-out...