Tutorial by Examples: a

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

The Data.Vector Module

The Data.Vector module provided by the vector is a high performance library for working with arrays. Once you've imported Data.Vector, it's easy to start using a Vector: Prelude> import Data.Vector Prelude Data.Vector> let a = fromList [2,3,4] Prelude Data.Vector> a fromList [2,3,4]...

Haskell Language • Vectors

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

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

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

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

Advanced Insertion Commands and Shortcuts

Here is a quick reference for advanced insertion, formatting, and filtering commands/shortcuts. Command/ShortcutResultg + ? + mPerform rot13 encoding, on movement mn + ctrl + a+n to number under cursorn + ctrl + x-n to number under cursorg + q+ mFormat lines of movement m to fixed width:rce wCenter...

vim • Inserting text

Finding information about a crash

When your app crashes, Xcode will enter the debugger and show you more information about the crash: The most important parts are: The red arrow The red arrow displays which line of code crashed & why it crashed. The debugger console Many crashes log more information to the debugger consol...

iOS • Debugging Crashes