Tutorial by Examples: n

Function Documentation

C-h f runs the function describe-function, which displays information on the usage and purpose of a given function. This is especially useful for functions that do not have a mapped key binding that can be used for documentation lookup via C-h k.

emacs • Help Within Emacs

Atomic Blocks with Software Transactional Memory

Another powerful & mature concurrency tool in Haskell is Software Transactional Memory, which allows for multiple threads to write to a single variable of type TVar a in an atomic manner. TVar a is the main type associated with the STM monad and stands for transactional variable. They're used m...

Haskell Language • Concurrency

Filtering a Vector

Filter odd elements: Prelude Data.Vector> Data.Vector.filter odd y fromList [1,3,5,7,9,11] :: Data.Vector.Vector

Haskell Language • Vectors

Mapping (`map`) and Reducing (`fold`) a Vector

Vectors can be map'd and fold'd,filter'd andzip`'d: Prelude Data.Vector> Data.Vector.map (^2) y fromList [0,1,4,9,16,25,36,49,64,81,100,121] :: Data.Vector.Vector Reduce to a single value: Prelude Data.Vector> Data.Vector.foldl (+) 0 y 66

Haskell Language • Vectors

Working on Multiple Vectors

Zip two arrays into an array of pairs: Prelude Data.Vector> Data.Vector.zip y y fromList [(0,0),(1,1),(2,2),(3,3),(4,4),(5,5),(6,6),(7,7),(8,8),(9,9),(10,10),(11,11)] :: Data.Vector.Vector

Haskell Language • Vectors

Filtering hashes

select returns a new hash with key-value pairs for which the block evaluates to true. { :a => 1, :b => 2, :c => 3 }.select { |k, v| k != :a && v.even? } # => { :b => 2 } When you will not need the key or value in a filter block, the convention is to use an _ in that place:...

Ruby Language • Hashes

Set Operations on Hashes

Intersection of Hashes To get the intersection of two hashes, return the shared keys the values of which are equal: hash1 = { :a => 1, :b => 2 } hash2 = { :b => 2, :c => 3 } hash1.select { |k, v| (hash2.include?(k) && hash2[k] == v) } # => { :b => 2 } Union (...

Ruby Language • Hashes

The Answer

Vim knows The Answer: :help 42 Vim will open the usr_42.txt document from the manual and show the following text: What is the meaning of life, the universe and everything? 42 Douglas Adams, the only person who knew what this question really was about is now dead, unfortunately. So now you m...

vim • Easter Eggs

Compile and sign schema

Cleaning and compiling code for iPhone, on project MyProject for schema Qa: xcrun xcodebuild clean \ -workspace "MyProject.xcworkspace" \ -scheme "YourScheme" \ -sdk iphoneos \ -configuration Debug \ archive \ -archivePath builds/MyProject.xcarchive...

Xcode • Command Line Tools

Memory management rules when using manual reference counting.

These rules apply only if you use manual reference counting! You own any object you create By calling a method whose name begins with alloc, new, copy or mutableCopy. For example: NSObject *object1 = [[NSObject alloc] init]; NSObject *object2 = [NSObject new]; NSObject *object3 = [object2 ...

Objective-C Language • Memory Management

One View, Multiple Forms

Here is a quick example of using multiple forms in one Django view. from django.contrib import messages from django.views.generic import TemplateView from .forms import AddPostForm, AddCommentForm from .models import Comment class AddCommentView(TemplateView): post_form_class = AddPo...

Django • Class based views

Install packages

To install a new package, e.g. aeson: cabal install aeson

Haskell Language • Cabal

Working with sandboxes

A Haskell project can either use the system wide packages or use a sandbox. A sandbox is an isolated package database and can prevent dependency conflicts, e. g. if multiple Haskell projects use different versions of a package. To initialize a sandbox for a Haskell package go to its directory and r...

Haskell Language • Cabal

Managing Open Split Windows (Keyboard Shortcuts)

After you have opened a split window in vim (as demonstrated by many examples under this tag) then you will likely want to control windows quickly. Here is how to control split windows using keyboard shortcuts. Move to split Above/Below: Ctrl + w and k Ctrl + w and j Move to split Left/Right...

vim • Split windows

Window Object Properties

The Window Object contains the following properties. PropertyDescriptionwindow.closedWhether the window has been closedwindow.lengthNumber of <iframe> elements in windowwindow.nameGets or sets the name of the windowwindow.innerHeightHeight of windowwindow.innerWidthWidth of windowwindow.scree...

JavaScript • BOM (Browser Object Model)

Sending HTML Email Using mail()

<?php $to = '[email protected]'; $subject = 'Sending an HTML email using mail() in PHP'; $message = '<html><body>This paragraph is bold.This text is italic.</body></html>'; $headers =...

PHP • Sending Email

Obtain class that satisfies generic parameter at runtime

Many unbound generic parameters, like those used in a static method, cannot be recovered at runtime (see Other Threads on Erasure). However there is a common strategy employed for accessing the type satisfying a generic parameter on a class at runtime. This allows for generic code that depends on ac...

Java Language • Generics

Denying access from IPs to files/directories

# Deny access to a directory from the IP 255.0.0.0 <Directory /path/to/directory> order allow,deny deny from 255.0.0.0 allow from all </Directory> # Deny access to a file from the IP 255.0.0.0 <FilesMatch "^\.ht"> order allow,deny deny fro...

Hypertext Access file • Denying Access

Easy way: python-social-auth

python-social-auth is a framework that simplifies the social authentication and authorization mechanism. It contains many social backends (Facebook, Twitter, Github, LinkedIn, etc.) INSTALL First we need to install the python-social-auth package with pip install python-social-auth or download ...

Django • Django and Social Networks

Installation or Setup

Synopsis A fully functional demo of Firebase v3 Web authentication viewable here. Sign in with Facebook, Github, Google, Twitter, password based, and anonymous accounts. The code, available on Github, is easy to read and follow and is well documented. The focus is on the fully functional authent...

firebase-authentication • Getting started with firebase-authentication