First, the famous inverse sqrt routine famous by its use in John Carmack’s game Doom. Credited to Greg Walsh. 32  Bit float magic number – 0x5f3759df. Works using a trick with float number binary representation:

float InvSqrt(float x)
{
  union {
    float f;
    int i;
  } tmp;
  tmp.f = x;
  tmp.i = 0x5f3759df - (tmp.i >> 1);
  float y = tmp.f;
  return y * (1.5f - 0.5f * x * y * y);
}

Its commonly used for vector normalization, since you multiply each vector component with InvSqrt, but can be used for other purposes. More info:
Chris Lomont, http://www.lomont.org/Math/Papers/2003/InvSqrt.pdf

Another good link for fast sqrt routines:
http://ilab.usc.edu/wiki/index.php/Fast_Square_Root

//TODO fast pow and fast log routines and one more VERY fast approximation of sqrt

… to be more detailed and continued … happy coding

The goal of Appirater class is to encourage your satisfied user’s to rate your app.

Appirater integration in your application is really easy. When you add it, every time the user launches your app, Appirater will see if they’ve used the app for 30 days and launched it at least 15 times. If they have, they’ll be asked to rate the app, and then be taken to your app’s review page in the App Store. If you release a new version of your app, Appirater will again wait until the new version has been used 15 times for 30 days and then prompt the user again for another review. Optionally, you can adjust the days to wait, and the launch number.

Checkout the class at:

• Developer page
• GitHub repository

You can use any content: url, image, piece of text, or file and just say “hey ShareKit, share this“,  ShareKit will present the user with a list of services that support the content they are sharing, handle logging them into the service, prompt for any additional information such as a caption, and display an activity indicator while uploading.

Really easy to integrate and use.

You can use multiple or just individual services (Facebook, Twitter, Delicious, Google reader etc.).

You can find more info on:

• Developer website
• Framework website
• GitHub repository

Tapku Software (The author of Attic, Super Research Idea Generator and Time Keeper Pro iPhone apps) has released an iPhone UI class library called Tapku Library.

TapkuLibrary is a collection of iPhone classes intended for broad use in applications. The framework contains set of classes to create user interface elements in your app, like coverflow, charting and calendar. It also includes new TableView cells, helper classes for easily creating http POST requests and class for detecting shake events using accelerometer.

Some of the classes are not yet that good. CoverFlow for example has bad physics, and has some slowdowns, but it will be improved over time. I’m sure you will find some usage for the classes, at least you can use them as a starting point when developing your own app, to speed up development process.

Library is open source, licensed under the Apache License, Version 2.0. You can get it on its github repository: http://github.com/devinross/tapkulibrary

UICallOutView is a private class in UIKit that produces “annotation views” used in Maps application.

Hendrik Holtmann (The author of iPhone app eCurrency) did fine work porting mono touch class, MonoTouchCalloutView, made by Ed Anuff.

You can download the class with example project included here:
http://dl.dropbox.com/u/363242/CallOutView.zip

Original blog post: http://www.eidac.de/?p=183