Tutorial by Examples: ch

The =~ operator attempts to match a regular expression (set apart by /) to a string: my $str = "hello world"; print "Hi, yourself!\n" if $str =~ /^hello/; /^hello/ is the actual regular expression. The ^ is a special character that tells the regular expression to start with ...

(Collects a certain number of total items from 2-3 inputs and groups them into a Tuple of collections of data items) BatchedJoinBlock<T1, T2,…> is in a sense a combination of BatchBlock and JoinBlock<T1, T2,…>. Whereas JoinBlock<T1, T2,…> is used to aggregate one input from each ...

(Groups a certain number of sequential data items into collections of data items) BatchBlock combines N single items into one batch item, represented as an array of elements. An instance is created with a specific batch size, and the block then creates a batch as soon as it’s received that number o...

Conceptually, integrate 3rd party REST APIs can be as simple as adding the http package and making a call to the external endpoint. meteor add http HTTP.get('http://foo.net/api/bar/');

We can also use macros for making code easier to read and write. For example we can implement macros for implementing the foreach construct in C for some data structures like singly- and doubly-linked lists, queues, etc. Here is a small example. #include <stdio.h> #include <stdlib.h>...

Microbenchmark is useful for estimating the time taking for otherwise fast procedures. For example, consider estimating the time taken to print hello world. system.time(print("hello world")) # [1] "hello world" # user system elapsed # 0 0 0 This i...

4.0 Instead of the ForEach-Object cmdlet, the here is also the possibility to use a ForEach method directly on object arrays like so (1..10).ForEach({$_ * $_}) or - if desired - the parentheses around the script block can be omitted (1..10).ForEach{$_ * $_} Both will result in the output ...

A branch is just a pointer to a commit, so you can freely move it around. To make it so that the branch is referring to the commit aabbcc, issue the command git reset --hard aabbcc Please note that this will overwrite your branch's current commit, and as so, its entire history. You might loose s...

This example shows how Stopwatch can be used to benchmark a block of code. using System; using System.Diagnostics; public class Benchmark : IDisposable { private Stopwatch sw; public Benchmark() { sw = Stopwatch.StartNew(); } public voi...

In order to check whether a value is NaN, isnull() or notnull() functions can be used. In [1]: import numpy as np In [2]: import pandas as pd In [3]: ser = pd.Series([1, 2, np.nan, 4]) In [4]: pd.isnull(ser) Out[4]: 0 False 1 False 2 True 3 False dtype: bool Note that n...

// Checks a string to see if it is a palindrome bool function IsPalindrome(string input) { if (input.size() <= 1) { return true; } else if (input[0] == input[input.size() - 1]) { return IsPalindrome(input.substr(1,input.size() - 2)); } else { r...

One of the most useful queries for end users of large RDBMS's is a search of an information schema. Such a query allows users to rapidly find database tables containing columns of interest, such as when attempting to relate data from 2 tables indirectly through a third table, without existing knowl...

There are use cases when you might want to rename your app directory to something else. In Laravel4 you could just change a config entry, here's one way to do it in Laravel5. In this example we'll be renaming the app directory to src. Override Application class The directories name app is hardcod...

Implementing two-way-data-binding, to achieve the result from the previous example, could be done with two core functions: $digest is called after a user interaction (binding DOM=>variable) $watch sets a callback to be called after variable changes (binding variable=>DOM) note: this is ...

CSS resets take separate approaches to browser defaults. Eric Meyer’s Reset CSS has been around for a while. His approach nullifies many of the browser elements that have been known to cause problems right off the back. The following is from his version (v2.0 | 20110126) CSS Reset. html, body, di...

Elixir matches a function call to its body based on the value of its arguments. defmodule Math do def factorial(0): do: 1 def factorial(n): do: n * factorial(n - 1) end Here, factorial of positive numbers matches the second clause, while factorial(0) matches the first. (ignoring negat...

To clone a specific branch of a repository, type --branch <branch name> before the repository url: git clone --branch <branch name> <url> [directory] To use the shorthand option for --branch, type -b. This command downloads entire repository and checks out <branch name>. ...

template<class InputIterator, class Function> Function for_each(InputIterator first, InputIterator last, Function f); Effects: Applies f to the result of dereferencing every iterator in the range [first, last) starting from first and proceeding to last - 1. Parameters: first, last -...

To change password of current user just type: sudo passwd It will ask you to enter your current password: [sudo] password for <user>: And then you will be asked to enter new password: Enter new UNIX password: And finally you will be asked to re-enter your password: Retype new UNIX...

As we know that we should use synchronized keyword to make execution of a method or block exclusive. But few of us may not be aware of one more important aspect of using synchronized and volatile keyword: apart from making a unit of code atomic, it also provides read / write barrier. What is this re...