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• Learning content for MCSDs: Web Applications and Windows Store Apps using HTML5

  Recently, I started again to learn for various Microsoft certifications. First candidate on my way to MSCD: Web Applications is the Exam 70-480: Programming in HTML5 with JavaScript and CSS3. Motivation to go for a Microsoft exam I guess, this is quite personal but let me briefly describe my intentions to go that exam. First, I'm doing web development since the 1990's. Working with HTML, CSS and Javascript is happening almost daily in my workspace. And honestly, I do not only do 'pure' web development but already integrated several HTML/CSS/Javascript frontend UIs into an existing desktop application (written in Visual FoxPro) inclusive two-way communication and data exchange. Hm, might be an interesting topic for another blog article here... Second, this exam has a very interesting aspect which is listed at the bottom of the exam's details: Credit Toward Certification When you pass Exam 70-480: Programming in HTML5 with JavaScript and CSS3, you complete the requirements for the following certification(s): Programming in HTML5 with JavaScript and CSS3 Specialist Exam 70-480: Programming in HTML5 with JavaScript and CSS3: counts as credit toward the following certification(s): MCSD: Web Applications MCSD: Windows Store Apps using HTML5 So, passing one single exam will earn you specialist certification straight-forward, and opens the path to higher levels of certifications. Preparations and learning path Well, due to a newsletter from Microsoft Learning (MSL) I caught interest in picking up the circumstances and learning materials for this particular exam. As of writing this article there is a promotional / voucher code available which enables you to register for this exam for free! Simply register yourself with or log into your existing account at Prometric, choose the exam for a testing facility near to you and enter the voucher code HTMLJMP (available through 31.03.2013 or while supplies last). Hurry up, there are restrictions... As stated above, I'm already very familiar with web development and the programming flavours involved into this. But of course, it is always good to freshen up your knowledge and reflect on yourself. Microsoft is putting a lot of effort to attract any kind of developers into the 'App Development'. Whether it is for the Windows 8 Store or the Windows Phone 8 Store, doesn't really matter. They simply need more apps. This demand for skilled developers also comes with a nice side-effect: Lots and lots of material to study. During the first couple of hours, I could easily gather high quality preparation material - again for free! Following is just a small list of starting points. If you have more resources, please drop me a message in the comment section, and I'll be glad to update this article accordingly. Developing HTML5 Apps Jump Start This is an accelerated jump start video course on development of HTML5 Apps for Windows 8. There are six modules that are split into two video sessions per module. Very informative and intense course material. This is packed stuff taken from an official preparation course for exam 70-480. Developing Windows Store Apps with HTML5 Jump Start Again, an accelerated preparation video course on Windows 8 Apps. There are six modules with two video sessions each which will catapult you to your exam. This is also related to preps for exam 70-481. Programming Windows 8 Apps with HTML, CSS, and JavaScript Kraig Brockschmidt delves into the ups and downs of Windows 8 App development over 800+ pages. Great eBook to read, study, and to practice the samples - best of all, it's for free. codeSHOW() This is a Windows 8 HTML/JS project with the express goal of demonstrating simple development concepts for the Windows 8 platform. Code, code and more code... absolutely great stuff to study and practice. Microsoft Virtual Academy I already wrote about the MVA in a previous article. Well, if you haven't registered yourself yet, now is the time. The list is not complete for sure, but this might keep you busy for at least one or even two weeks to go through the material. Please don't hesitate to add more resources in the comment section. Right now, I'm already through all videos once, and digging my way through chapter 4 of Kraig's book. Additional material - Pluralsight Apart from those free online resources, I also following some courses from the excellent library of Pluralsight. They already have their own section for Windows 8 development, but of course, you get companion material about HTML5, CSS and Javascript in other sections, too. Introduction to Building Windows 8 Applications Building Windows 8 Applications with JavaScript and HTML Selling Windows 8 Apps HTML5 Fundamentals Using HTML5 and CSS3 HTML5 Advanced Topics CSS3 etc... Interesting to see that Michael Palermo provides his course material on multiple platforms. Fantastic! You might also pay a visit to his personal blog. Hm, it just came to my mind that Aaron Skonnard of Pluralsight publishes so-called '24 hours Learning Paths' based on courses available in the course library. Would be interested to see a combination for Windows 8 App development using HTML5, CSS3 and Javascript in the future. Recommended workspace environment Well, you might have guessed it but this requires Windows 8, Visual Studio 2012 Express or another flavour, and a valid Developers License. Due to an MSDN subscription I working on VS 2012 Premium with some additional tools by Telerik. Honestly, the fastest way to get you up and running for Windows 8 App development is the source code archive of codeSHOW(). It does not only give you all source code in general but contains a couple of SDKs like Bing Maps, Microsoft Advertising, Live ID, and Telerik Windows 8 controls... for free! Hint: Get the Windows Phone 8 SDK as well. Don't worry, while you are studying the material for Windows 8 you will be able to leverage from this knowledge to development for the phone platform, too. It takes roughly one to two hours to get your workspace and learning environment, at least this was my time frame due to slow internet connection and an aged spare machine. ;-) Oh, before I forget to mention it, as soon as you're done, go quickly to the Windows Store and search for ClassBrowserPlus. You might not need it ad hoc for your development using HTML5, CSS and Javascript but I think that it is a great developer's utility that enables you to view the properties, methods and events (along with help text) for all Windows 8 classes. It's always good to look behind the scenes and to explore how it is made. Idea: Start/join a learning group The way you learn new things or intensify your knowledge in a certain technology is completely up to your personal preference. Back in my days at the university, we used to meet once or twice a week in a small quiet room to exchange our progress, questions and problems we ran into. In general, I recommend to any software craftsman to lift your butt and get out to exchange with other developers. Personally, I like this approach, as it gives you new points of view and an insight into others' own experience with certain techniques and how they managed to solve tricky issues. Just keep it relaxed and not too formal after all, and you might a have a good time away from your dull office desk. Give your machine a break, too.

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• Self-signed certificates for a known community

  - by costlow

  Recently announced changes scheduled for Java 7 update 51 (January 2014) have established that the default security slider will require code signatures and the Permissions Manifest attribute. Code signatures are a common practice recommended in the industry because they help determine that the code your computer will run is the same code that the publisher created. This post is written to help users that need to use self-signed certificates without involving a public Certificate Authority. The role of self-signed certificates within a known community You may still use self-signed certificates within a known community. The difference between self-signed and purchased-from-CA is that your users must import your self-signed certificate to indicate that it is valid, whereas Certificate Authorities are already trusted by default. This works for known communities where people will trust that my certificate is mine, but does not scale widely where I cannot actually contact or know the systems that will need to trust my certificate. Public Certificate Authorities are widely trusted already because they abide by many different requirements and frequent checks. An example would be students in a university class sharing their public certificates on a mailing list or web page, employees publishing on the intranet, or a system administrator rolling certificates out to end-users. Managed machines help this because you can automate the rollout, but they are not required -- the major point simply that people will trust and import your certificate. How to distribute self-signed certificates for a known community There are several steps required to distribute a self-signed certificate to users so that they will properly trust it. These steps are: Creating a public/private key pair for signing. Exporting your public certificate for others Importing your certificate onto machines that should trust you Verify work on a different machine Creating a public/private key pair for signing Having a public/private key pair will give you the ability both to sign items yourself and issue a Certificate Signing Request (CSR) to a certificate authority. Create your public/private key pair by following the instructions for creating key pairs.Every Certificate Authority that I looked at provided similar instructions, but for the sake of cohesiveness I will include the commands that I used here: Generate the key pair.keytool -genkeypair -alias erikcostlow -keyalg EC -keysize 571 -validity 730 -keystore javakeystore_keepsecret.jks Provide a good password for this file. The alias "erikcostlow" is my name and therefore easy to remember. Substitute your name of something like "mykey." The sigalg of EC (Elliptical Curve) and keysize of 571 will give your key a good strong lifetime. All keys are set to expire. Two years or 730 days is a reasonable compromise between not-long-enough and too-long. Most public Certificate Authorities will sign something for one to five years. You will be placing your keys in javakeystore_keepsecret.jks -- this file will contain private keys and therefore should not be shared. If someone else gets these private keys, they can impersonate your signature. Please be cautious about automated cloud backup systems and private key stores. Answer all the questions. It is important to provide good answers because you will stick with them for the "-validity" days that you specified above.What is your first and last name?  [Unknown]:  First LastWhat is the name of your organizational unit?  [Unknown]:  Line of BusinessWhat is the name of your organization?  [Unknown]:  MyCompanyWhat is the name of your City or Locality?  [Unknown]:  City NameWhat is the name of your State or Province?  [Unknown]:  CAWhat is the two-letter country code for this unit?  [Unknown]:  USIs CN=First Last, OU=Line of Business, O=MyCompany, L=City, ST=CA, C=US correct?  [no]:  yesEnter key password for <erikcostlow>        (RETURN if same as keystore password): Verify your work:keytool -list -keystore javakeystore_keepsecret.jksYou should see your new key pair. Exporting your public certificate for others Public Key Infrastructure relies on two simple concepts: the public key may be made public and the private key must be private. By exporting your public certificate, you are able to share it with others who can then import the certificate to trust you. keytool -exportcert -keystore javakeystore_keepsecret.jks -alias erikcostlow -file erikcostlow.cer To verify this, you can open the .cer file by double-clicking it on most operating systems. It should show the information that you entered during the creation prompts. This is the file that you will share with others. They will use this certificate to prove that artifacts signed by this certificate came from you. If you do not manage machines directly, place the certificate file on an area that people within the known community should trust, such as an intranet page. Import the certificate onto machines that should trust you In order to trust the certificate, people within your known network must import your certificate into their keystores. The first step is to verify that the certificate is actually yours, which can be done through any band: email, phone, in-person, etc. Known networks can usually do this Determine the right keystore: For an individual user looking to trust another, the correct file is within that user’s directory.e.g. USER_HOME\AppData\LocalLow\Sun\Java\Deployment\security\trusted.certs For system-wide installations, Java’s Certificate Authorities are in JAVA_HOMEe.g. C:\Program Files\Java\jre8\lib\security\cacerts File paths for Mac and Linux are included in the link above. Follow the instructions to import the certificate into the keystore. keytool -importcert -keystore THEKEYSTOREFROMABOVE -alias erikcostlow -file erikcostlow.cer In this case, I am still using my name for the alias because it’s easy for me to remember. You may also use an alias of your company name. Scaling distribution of the import The easiest way to apply your certificate across many machines is to just push the .certs or cacerts file onto them. When doing this, watch out for any changes that people would have made to this file on their machines. Trusted.certs: When publishing into user directories, your file will overwrite any keys that the user has added since last update. CACerts: It is best to re-run the import command with each installation rather than just overwriting the file. If you just keep the same cacerts file between upgrades, you will overwrite any CAs that have been added or removed. By re-importing, you stay up to date with changes. Verify work on a different machine Verification is a way of checking on the client machine to ensure that it properly trusts signed artifacts after you have added your signing certificate. Many people have started using deployment rule sets. You can validate the deployment rule set by: Create and sign the deployment rule set on the computer that holds the private key. Copy the deployment rule set on to the different machine where you have imported the signing certificate. Verify that the Java Control Panel’s security tab shows your deployment rule set. Verifying an individual JAR file or multiple JAR files You can test a certificate chain by using the jarsigner command. jarsigner -verify filename.jar If the output does not say "jar verified" then run the following command to see why: jarsigner -verify -verbose -certs filename.jar Check the output for the term “CertPath not validated.”

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• Ideal programming language learning sequence?

  - by Gulshan

  What do you think? What is the ideal programming language learning sequence which will cover most of the heavily used languages and paradigms today as well as help to grasp common programming basics, ideas and practices? You can even suggest learning sequence for paradigms rather than languages. N.B. : This is port of the question I asked in stackoverflow and was closed for being subjective and argumentative.

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• Learning how to integrate JavaScript with other languages

  - by beacon

  After learning JavaScript syntax, what are some good resources for learning about integrating JavaScript with other languages (HTML, XML, CSS, PHP) to create real, useful applications? I'm most interested in reading articles or other people's code - not so interested in books. Basically, I'm looking to move from programming puzzle-solvers to programming complex applications and could use some advice.

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• Ideal programming language learning sequence? [closed]

  - by Gulshan

  What do you think? What is the ideal programming language learning sequence which will cover most of the heavily used languages and paradigms today as well as help to grasp common programming basics, ideas and practices? You can even suggest learning sequence for paradigms rather than languages. N.B. : This is port of the question I asked in stackoverflow and was closed for being subjective and argumentative.

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• Learning How to SEO

  Like anything, learning is a series of small steps that allow you to gain knowledge and information. In the case of Search Engine Optimization the steps will provide you with a skill that can advance your website in the search engine results pages while increasing your business bottom line. So there are advantages to learning how to SEO your own website and the outcome can be profitable.

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• Python: nonblocking read from stdout of threaded subprocess

  - by sberry2A

  I have a script (worker.py) that prints unbuffered output in the form... 1 2 3 . . . n where n is some constant number of iterations a loop in this script will make. In another script (service_controller.py) I start a number of threads, each of which starts a subprocess using subprocess.Popen(stdout=subprocess.PIPE, ...); Now, in my main thread (service_controller.py) I want to read the output of each thread's worker.py subprocess and use it to calculate an estimate for the time remaining till completion. I have all of the logic working that reads the stdout from worker.py and determines the last printed number. The problem is that I can not figure out how to do this in a non-blocking way. If I read a constant bufsize then each read will end up waiting for the same data from each of the workers. I have tried numerous ways including using fcntl, select + os.read, etc. What is my best option here? I can post my source if needed, but I figured the explanation describes the problem well enough. Thanks for any help here. EDIT Adding sample code I have a worker that starts a subprocess. class WorkerThread(threading.Thread): def __init__(self): self.completed = 0 self.process = None self.lock = threading.RLock() threading.Thread.__init__(self) def run(self): cmd = ["/path/to/script", "arg1", "arg2"] self.process = subprocess.Popen(cmd, stdout=subprocess.PIPE, bufsize=1, shell=False) #flags = fcntl.fcntl(self.process.stdout, fcntl.F_GETFL) #fcntl.fcntl(self.process.stdout.fileno(), fcntl.F_SETFL, flags | os.O_NONBLOCK) def get_completed(self): self.lock.acquire(); fd = select.select([self.process.stdout.fileno()], [], [], 5)[0] if fd: self.data += os.read(fd, 1) try: self.completed = int(self.data.split("\n")[-2]) except IndexError: pass self.lock.release() return self.completed I then have a ThreadManager. class ThreadManager(): def __init__(self): self.pool = [] self.running = [] self.lock = threading.Lock() def clean_pool(self, pool): for worker in [x for x in pool is not x.isAlive()]: worker.join() pool.remove(worker) del worker return pool def run(self, concurrent=5): while len(self.running) + len(self.pool) > 0: self.clean_pool(self.running) n = min(max(concurrent - len(self.running), 0), len(self.pool)) if n > 0: for worker in self.pool[0:n]: worker.start() self.running.extend(self.pool[0:n]) del self.pool[0:n] time.sleep(.01) for worker in self.running + self.pool: worker.join() and some code to run it. threadManager = ThreadManager() for i in xrange(0, 5): threadManager.pool.append(WorkerThread()) threadManager.run() I have stripped out a log of the other code in hopes to try to pinpoint the issue.

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• C# Toolbox: Debug-able, Self-Installable Windows Service Template Redux

  - by James Michael Hare

  I had written a pair of posts before about creating a debug-able and self-installing windows service template in C#.  This is a template I began creating to ease creating windows services and to take some of the mundane tasks out of the coding effort.  The original posts were here: C# Windows Services (1 of 2) - Debug-able Windows Services C# Windows Services (2 of 2) - Self-Installing Windows Services But at the time, though I gave the code samples I didn't have a downloadable for of the template on the blog.  After getting many requests for the actual source, I zipped it up and am posting it with this blog entry.  Click on the link below to download the archive.  The password on the archive is, imaginatively enough, password.  Hope you enjoy and please feel free to comment and suggest changes! Debug-able, Self-Installing Windows Service Template download Enjoy! Tweet Technorati Tags: C#,Windows Service,Toolbox

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• Can I avoid a threaded UDP socket in Python dropping data?

  - by 666craig

  First off, I'm new to Python and learning on the job, so be gentle! I'm trying to write a threaded Python app for Windows that reads data from a UDP socket (thread-1), writes it to file (thread-2), and displays the live data (thread-3) to a widget (gtk.Image using a gtk.gdk.pixbuf). I'm using queues for communicating data between threads. My problem is that if I start only threads 1 and 3 (so skip the file writing for now), it seems that I lose some data after the first few samples. After this drop it looks fine. Even by letting thread 1 complete before running thread 3, this apparent drop is still there. Apologies for the length of code snippet (I've removed the thread that writes to file), but I felt removing code would just prompt questions. Hope someone can shed some light :-) import socket import threading import Queue import numpy import gtk gtk.gdk.threads_init() import gtk.glade import pygtk class readFromUDPSocket(threading.Thread): def __init__(self, socketUDP, readDataQueue, packetSize, numScans): threading.Thread.__init__(self) self.socketUDP = socketUDP self.readDataQueue = readDataQueue self.packetSize = packetSize self.numScans = numScans def run(self): for scan in range(1, self.numScans + 1): buffer = self.socketUDP.recv(self.packetSize) self.readDataQueue.put(buffer) self.socketUDP.close() print 'myServer finished!' class displayWithGTK(threading.Thread): def __init__(self, displayDataQueue, image, viewArea): threading.Thread.__init__(self) self.displayDataQueue = displayDataQueue self.image = image self.viewWidth = viewArea[0] self.viewHeight = viewArea[1] self.displayData = numpy.zeros((self.viewHeight, self.viewWidth, 3), dtype=numpy.uint16) def run(self): scan = 0 try: while True: if not scan % self.viewWidth: scan = 0 buffer = self.displayDataQueue.get(timeout=0.1) self.displayData[:, scan, 0] = numpy.fromstring(buffer, dtype=numpy.uint16) self.displayData[:, scan, 1] = numpy.fromstring(buffer, dtype=numpy.uint16) self.displayData[:, scan, 2] = numpy.fromstring(buffer, dtype=numpy.uint16) gtk.gdk.threads_enter() self.myPixbuf = gtk.gdk.pixbuf_new_from_data(self.displayData.tostring(), gtk.gdk.COLORSPACE_RGB, False, 8, self.viewWidth, self.viewHeight, self.viewWidth * 3) self.image.set_from_pixbuf(self.myPixbuf) self.image.show() gtk.gdk.threads_leave() scan += 1 except Queue.Empty: print 'myDisplay finished!' pass def quitGUI(obj): print 'Currently active threads: %s' % threading.enumerate() gtk.main_quit() if __name__ == '__main__': # Create socket (IPv4 protocol, datagram (UDP)) and bind to address socketUDP = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) host = '192.168.1.5' port = 1024 socketUDP.bind((host, port)) # Data parameters samplesPerScan = 256 packetsPerSecond = 1200 packetSize = 512 duration = 1 # For now, set a fixed duration to log data numScans = int(packetsPerSecond * duration) # Create array to store data data = numpy.zeros((samplesPerScan, numScans), dtype=numpy.uint16) # Create queue for displaying from readDataQueue = Queue.Queue(numScans) # Build GUI from Glade XML file builder = gtk.Builder() builder.add_from_file('GroundVue.glade') window = builder.get_object('mainwindow') window.connect('destroy', quitGUI) view = builder.get_object('viewport') image = gtk.Image() view.add(image) viewArea = (1200, samplesPerScan) # Instantiate & start threads myServer = readFromUDPSocket(socketUDP, readDataQueue, packetSize, numScans) myDisplay = displayWithGTK(readDataQueue, image, viewArea) myServer.start() myDisplay.start() gtk.gdk.threads_enter() gtk.main() gtk.gdk.threads_leave() print 'gtk.main finished!'

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• Can I avoid a threaded UDP socket in Pyton dropping data?

  - by 666craig

  First off, I'm new to Python and learning on the job, so be gentle! I'm trying to write a threaded Python app for Windows that reads data from a UDP socket (thread-1), writes it to file (thread-2), and displays the live data (thread-3) to a widget (gtk.Image using a gtk.gdk.pixbuf). I'm using queues for communicating data between threads. My problem is that if I start only threads 1 and 3 (so skip the file writing for now), it seems that I lose some data after the first few samples. After this drop it looks fine. Even by letting thread 1 complete before running thread 3, this apparent drop is still there. Apologies for the length of code snippet (I've removed the thread that writes to file), but I felt removing code would just prompt questions. Hope someone can shed some light :-) import socket import threading import Queue import numpy import gtk gtk.gdk.threads_init() import gtk.glade import pygtk class readFromUDPSocket(threading.Thread): def __init__(self, socketUDP, readDataQueue, packetSize, numScans): threading.Thread.__init__(self) self.socketUDP = socketUDP self.readDataQueue = readDataQueue self.packetSize = packetSize self.numScans = numScans def run(self): for scan in range(1, self.numScans + 1): buffer = self.socketUDP.recv(self.packetSize) self.readDataQueue.put(buffer) self.socketUDP.close() print 'myServer finished!' class displayWithGTK(threading.Thread): def __init__(self, displayDataQueue, image, viewArea): threading.Thread.__init__(self) self.displayDataQueue = displayDataQueue self.image = image self.viewWidth = viewArea[0] self.viewHeight = viewArea[1] self.displayData = numpy.zeros((self.viewHeight, self.viewWidth, 3), dtype=numpy.uint16) def run(self): scan = 0 try: while True: if not scan % self.viewWidth: scan = 0 buffer = self.displayDataQueue.get(timeout=0.1) self.displayData[:, scan, 0] = numpy.fromstring(buffer, dtype=numpy.uint16) self.displayData[:, scan, 1] = numpy.fromstring(buffer, dtype=numpy.uint16) self.displayData[:, scan, 2] = numpy.fromstring(buffer, dtype=numpy.uint16) gtk.gdk.threads_enter() self.myPixbuf = gtk.gdk.pixbuf_new_from_data(self.displayData.tostring(), gtk.gdk.COLORSPACE_RGB, False, 8, self.viewWidth, self.viewHeight, self.viewWidth * 3) self.image.set_from_pixbuf(self.myPixbuf) self.image.show() gtk.gdk.threads_leave() scan += 1 except Queue.Empty: print 'myDisplay finished!' pass def quitGUI(obj): print 'Currently active threads: %s' % threading.enumerate() gtk.main_quit() if __name__ == '__main__': # Create socket (IPv4 protocol, datagram (UDP)) and bind to address socketUDP = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) host = '192.168.1.5' port = 1024 socketUDP.bind((host, port)) # Data parameters samplesPerScan = 256 packetsPerSecond = 1200 packetSize = 512 duration = 1 # For now, set a fixed duration to log data numScans = int(packetsPerSecond * duration) # Create array to store data data = numpy.zeros((samplesPerScan, numScans), dtype=numpy.uint16) # Create queue for displaying from readDataQueue = Queue.Queue(numScans) # Build GUI from Glade XML file builder = gtk.Builder() builder.add_from_file('GroundVue.glade') window = builder.get_object('mainwindow') window.connect('destroy', quitGUI) view = builder.get_object('viewport') image = gtk.Image() view.add(image) viewArea = (1200, samplesPerScan) # Instantiate & start threads myServer = readFromUDPSocket(socketUDP, readDataQueue, packetSize, numScans) myDisplay = displayWithGTK(readDataQueue, image, viewArea) myServer.start() myDisplay.start() gtk.gdk.threads_enter() gtk.main() gtk.gdk.threads_leave() print 'gtk.main finished!'

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• Update Rule in Temporal difference

  - by Betamoo

  The update rule TD(0) Q-Learning: Q(t-1) = (1-alpha) * Q(t-1) + (alpha) * (Reward(t-1) + gamma* Max( Q(t) ) ) Then take either the current best action (to optimize) or a random action (to explorer) Where MaxNextQ is the maximum Q that can be got in the next state... But in TD(1) I think update rule will be: Q(t-2) = (1-alpha) * Q(t-2) + (alpha) * (Reward(t-2) + gamma * Reward(t-1) + gamma * gamma * Max( Q(t) ) ) My question: The term gamma * Reward(t-1) means that I will always take my best action at t-1 .. which I think will prevent exploring.. Can someone give me a hint? Thanks

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• I'm making a simulated tv

  - by Jam

  I need to make a tv that shows the user the channel and the volume, and shows whether or not the television is on. I have the majority of the code made, but for some reason the channels won't switch. I'm fairly unfamiliar with how properties work, and I think that's what my problem here is. Help please. class Television(object): def __init__(self, __channel=1, volume=1, is_on=0): self.__channel=__channel self.volume=volume self.is_on=is_on def __str__(self): if self.is_on==1: print "The tv is on" print self.__channel print self.volume else: print "The television is off." def toggle_power(self): if self.is_on==1: self.is_on=0 return self.is_on if self.is_on==0: self.is_on=1 return self.is_on def get_channel(self): return channel def set_channel(self, choice): if self.is_on==1: if choice>=0 and choice<=499: channel=self.__channel else: print "Invalid channel!" else: print "The television isn't on!" channel=property(get_channel, set_channel) def raise_volume(self, up=1): if self.is_on==1: self.volume+=up if self.volume>=10: self.volume=10 print "Max volume!" else: print "The television isn't on!" def lower_volume(self, down=1): if self.is_on==1: self.volume-=down if self.volume<=0: self.volume=0 print "Muted!" else: print "The television isn't on!" def main(): tv=Television() choice=None while choice!="0": print \ """ Television 0 - Exit 1 - Toggle Power 2 - Change Channel 3 - Raise Volume 4 - Lower Volume """ choice=raw_input("Choice: ") print if choice=="0": print "Good-bye." elif choice=="1": tv.toggle_power() tv.__str__() elif choice=="2": change=raw_input("What would you like to change the channel to?") tv.set_channel(change) tv.__str__() elif choice=="3": tv.raise_volume() tv.__str__() elif choice=="4": tv.lower_volume() tv.__str__() else: print "\nSorry, but", choice, "isn't a valid choice." main() raw_input("Press enter to exit.")

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• How to learn Haskell

  - by anderstornvig

  For a few days I've tried to wrap my head around the functional programming paradigm in Haskell. I've done this by reading tutorials and watching screencasts, but nothing really seems to stick. Now, in learning various imperative/OO languages (like C, Java, PHP), excercises have been a good way for me to go. But since I don't really know what Haskell is capable of and because there are many new concepts to utilize, I haven't known where to start. So, how did you learn Haskell? What made you really "break the ice"? Also, any good ideas for beginning excercises?

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• What are the disadvantages of self-encapsulation?

  - by Dave Jarvis

  Background Tony Hoare's billion dollar mistake was the invention of null. Subsequently, a lot of code has become riddled with null pointer exceptions (segfaults) when software developers try to use (dereference) uninitialized variables. In 1989, Wirfs-Brock and Wikerson wrote: Direct references to variables severely limit the ability of programmers to re?ne existing classes. The programming conventions described here structure the use of variables to promote reusable designs. We encourage users of all object-oriented languages to follow these conventions. Additionally, we strongly urge designers of object-oriented languages to consider the effects of unrestricted variable references on reusability. Problem A lot of software, especially in Java, but likely in C# and C++, often uses the following pattern: public class SomeClass { private String someAttribute; public SomeClass() { this.someAttribute = "Some Value"; } public void someMethod() { if( this.someAttribute.equals( "Some Value" ) ) { // do something... } } public void setAttribute( String s ) { this.someAttribute = s; } public String getAttribute() { return this.someAttribute; } } Sometimes a band-aid solution is used by checking for null throughout the code base: public void someMethod() { assert this.someAttribute != null; if( this.someAttribute.equals( "Some Value" ) ) { // do something... } } public void anotherMethod() { assert this.someAttribute != null; if( this.someAttribute.equals( "Some Default Value" ) ) { // do something... } } The band-aid does not always avoid the null pointer problem: a race condition exists. The race condition is mitigated using: public void anotherMethod() { String someAttribute = this.someAttribute; assert someAttribute != null; if( someAttribute.equals( "Some Default Value" ) ) { // do something... } } Yet that requires two statements (assignment to local copy and check for null) every time a class-scoped variable is used to ensure it is valid. Self-Encapsulation Ken Auer's Reusability Through Self-Encapsulation (Pattern Languages of Program Design, Addison Wesley, New York, pp. 505-516, 1994) advocated self-encapsulation combined with lazy initialization. The result, in Java, would resemble: public class SomeClass { private String someAttribute; public SomeClass() { setAttribute( "Some Value" ); } public void someMethod() { if( getAttribute().equals( "Some Value" ) ) { // do something... } } public void setAttribute( String s ) { this.someAttribute = s; } public String getAttribute() { String someAttribute = this.someAttribute; if( someAttribute == null ) { setAttribute( createDefaultValue() ); } return someAttribute; } protected String createDefaultValue() { return "Some Default Value"; } } All duplicate checks for null are superfluous: getAttribute() ensures the value is never null at a single location within the containing class. Efficiency arguments should be fairly moot -- modern compilers and virtual machines can inline the code when possible. As long as variables are never referenced directly, this also allows for proper application of the Open-Closed Principle. Question What are the disadvantages of self-encapsulation, if any? (Ideally, I would like to see references to studies that contrast the robustness of similarly complex systems that use and don't use self-encapsulation, as this strikes me as a fairly straightforward testable hypothesis.)

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• Learning Objective-C for iPad/iPhone/iPod Development

  - by Jeff Julian

  I am learning how to write apps for the iPad/iPhone/iPod!  Why, well several reasons.  One reason, I have 5 devices in my house on the platform.  I had an iPad and iPhone, Michelle has an iPhone, and each of the kids have iPod Touches.  They are excellent devices for life management, entertainment, and learning.  I am amazed at how well the kids pick up on it and how much it effects the way they learn.  My two year old knows how to use it better than any other device we own and she is learning new words and letters so quickly. Because of this saturation at home, it would be fun to write some apps my family could use.  Some games to bring the hobby of development back into my life.  Second reason is we want to have a Geekswithblogs app for the iPhone and iPad.  We are not sure if it is purely informational (blog posts and tweets) or if members want to be able to publish from the app.  Creating a blog editor would be tough stuff, but could be just the right challenge. There are so many more reasons, but the last one that really makes me excited is that it is a new domain of development where I get excited when I think about writing apps.  That excitement level where I want to see if there are User Groups and if we are just watching TV, to break out the MBP and start working on it.  That excitement level where I could really read a development book cover to cover and not just use as a reference.  I really do like this feeling. Who knows how long this will last and I am definitely not leaving .NET.  Microsoft software will always be my main focus, but for the time, my hobby is changing and I am getting excited about development again.   Technorati Tags: Apple,iPad Development,Objective-C,New Frontiers Image: Courtesy of Apple

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• Gems In The Visual Studio 2010 Training Kit - Introduction to ASP.NET MVC: Learning Labs

  - by Jim Duffy

  Following up on my prior “gems post” is another nugget I found in the Visual Studio 2010 and .NET Framework 4 Training Kit. ASP.NET MVC has established quite a bit of momentum in the ASP.NET development community since it was introduced in early-ish 2009 though I’m sure there are many developers who haven’t had the time or opportunity to find out what it is, not to mention learn how to use it. If you’re one of those “I’ve heard of it but I’m not sure what it really is” developers then I suggest you start your research here. Ok, back to the gem. There are a number of fantastic MVC learning resources out there including the video tutorials on the ASP.NET MVC website. Another learning resource for your journey along the yellow brick road into ASP.NET MVC land are the hands-on learning labs contained in the Visual Studio 2010 and .NET Framework 4 Training Kit. These hands-on exercises walk you through the process of creating the “M”, the “V”s, and the “C”s of ASP.NET MVC and help you gain a solid foothold into the details of creating and understanding ASP.NET MVC applications. Have a day. :-|

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• Software vs Network Engineer (Salary, Difficulty, Learning, Happiness)

  - by B Z

  What are your thoughts on being a Software Engineer vs a Network Engineer? I've been on the software field for almost 10 years now and although I still have a great deal of fun (and challenges), I am starting to think it could be better on the "other" side. Not to degrade network engineers (i know there are many great ones out there), it seems (in general) their job is easier, the learning curve from average to good is not as steep, job is less stressful and pay is better on average. I think as software developer I could make the switch to networking and still enjoy working with computers and feel productive. I spend an enormous amount of time learning about software, practices, new technologies, new patters, etc...I think I could spend a much smaller amount of time learning about networking and be just as "good". What are your thoughts? EDIT: This is not about making easy money. Networking and Software are closely related, I love computers and programming, but if I can work with both, make more money and have less stress in my life and can spend more time with my family, then I am willing to consider a change and hence I am looking for advice that Do or Don't support this view.

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• Python progression path - From apprentice to guru

  - by Morlock

  Hi all, I've been learning, working, and playing with Python for a year and a half now. As a biologist slowly making the turn to bio-informatics, this language has been a the very core of all the major contributions I have made in the lab. (bash and R scripts have helped some too. My C++ capabilities are very not functional yet). I more or less fell in love with the way Python permits me to express beautiful solutions and also with the semantics of the language that allows such a natural flow from thoughts to workable code. What I would like to know from you is your answer to a kind of question I have seldom seen in this or other forums. Let me sum up what I do NOT want to ask first ;) I don't want to know how to QUICKLY learn Python Nor do I want to find out the best way to get acquainted with the language Finally, I don't want to know a 'one trick that does it all' approach. What I do want to know your opinion about, is: What are the steps YOU would recommend to a Python journeyman, from apprenticeship to guru status (feel free to stop wherever your expertise dictates it), in order that one IMPROVES CONSTANTLY, becoming a better and better Python coder, one step at a time. The kind of answers I would enjoy (but feel free to surprise the readership :P ), is formatted more or less like this: Read this (eg: python tutorial), pay attention to that kind of details Code for so manytime/problems/lines of code Then, read this (eg: this or that book), but this time, pay attention to this Tackle a few real-life problems Then, proceed to reading Y. Be sure to grasp these concepts Code for X time Come back to such and such basics or move further to... (you get the point :) This process depicts an iterative Learn/Code cycle, and I really care about knowing your opinion on what exactly one should pay attention to, at various stages, in order to progress CONSTANTLY (with due efforts, of course). If you come from a specific field of expertise, discuss the path you see as appropriate in this field. Thanks a lot for sharing your opinions and good Python coding!

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• Atom feed validator keeps showing Self reference doesn't match document location

  - by Dino

  I am creating an atom feed, but when I validate it I keep getting: Self reference doesn't match document location and the specific line that is causing the error is: <link rel="self" type="application/atom+xml" href="http://www.example.com/test.rss"/> Please can anyone advise what the error is? Ps. I noticed an up arrow just at the end of that line. (presumably something to do with that bbut not sure)

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• rhythmbox plugin code for hot key not working

  - by Bunny Rabbit

  def activate(self,shell): self.shell = shell self.copy_selected() self.action = gtk.Action ('foo','bar','baz',None) self.activate_id = self.action.connect ('activate', self.call_bk_fn,self.shell) self.action_group = gtk.ActionGroup ('hot_key_action_group') self.action_group.add_action_with_accel (self.action, "<control>E") uim = shell.get_ui_manager () uim.insert_action_group (self.action_group, 0) uim.ensure_update () def call_bk_fn(): print('hello world') i am using the above code in a plugin for rhythmbox ,and here i am trying to register the key ctr+e so that the call_bk_fn gets called whenever the key combination is pressed , but its not working why is that so ?

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• Self-Executing Anonymous Function vs Prototype

  - by Robotsushi

  In Javascript there are a few clearly prominent techniques for create and manage classes/namespaces in javascript. I am curious what situations warrant using one technique vs. the other. I want to pick one and stick with it moving forward. I write enterprise code that is maintained and shared across multiple teams, and I want to know what is the best practice when writing maintainable javascript ? I tend to prefer Self-Executing Anonymous Functions however I am curious what the community vote is on these techniques. Prototype : function obj() { } obj.prototype.test = function() { alert('Hello?'); }; var obj2 = new obj(); obj2.test(); Self-Closing Anonymous Function : //Self-Executing Anonymous Function (function( skillet, $, undefined ) { //Private Property var isHot = true; //Public Property skillet.ingredient = "Bacon Strips"; //Public Method skillet.fry = function() { var oliveOil; addItem( "\t\n Butter \n\t" ); addItem( oliveOil ); console.log( "Frying " + skillet.ingredient ); }; //Private Method function addItem( item ) { if ( item !== undefined ) { console.log( "Adding " + $.trim(item) ); } } }( window.skillet = window.skillet || {}, jQuery )); //Public Properties console.log( skillet.ingredient ); //Bacon Strips //Public Methods skillet.fry(); //Adding Butter & Fraying Bacon Strips //Adding a Public Property skillet.quantity = "12"; console.log( skillet.quantity ); //12 //Adding New Functionality to the Skillet (function( skillet, $, undefined ) { //Private Property var amountOfGrease = "1 Cup"; //Public Method skillet.toString = function() { console.log( skillet.quantity + " " + skillet.ingredient + " & " + amountOfGrease + " of Grease" ); console.log( isHot ? "Hot" : "Cold" ); }; }( window.skillet = window.skillet || {}, jQuery )); //end of skillet definition try { //12 Bacon Strips & 1 Cup of Grease skillet.toString(); //Throws Exception } catch( e ) { console.log( e.message ); //isHot is not defined } I feel that I should mention that the Self-Executing Anonymous Function is the pattern used by the jQuery team. Update When I asked this question I didn't truly see the importance of what I was trying to understand. The real issue at hand is whether or not to use new to create instances of your objects or to use patterns which do not require constructors of the use of the new keyword. I added my own answer, because in my opinion we should make use of patterns which don't use the new keyword. For more information please see my answer.

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• Strange Flash AS3 xml Socket behavior

  - by Rnd_d

  I have a problem which I can't understand. To understand it I wrote a socket client on AS3 and a server on python/twisted, you can see the code of both applications below. Let's launch two clients at the same time, arrange them so that you can see both windows and press connection button in both windows. Then press and hold any button. What I'm expecting: Client with pressed button sends a message "some data" to the server, then the server sends this message to all the clients(including the original sender) . Then each client moves right the button 'connectButton' and prints a message to the log with time in the following format: "min:secs:milliseconds". What is going wrong: The motion is smooth in the client that sends the message, but in all other clients the motion is jerky. This happens because messages to those clients arrive later than to the original sending client. And if we have three clients (let's name them A,B,C) and we send a message from A, the sending time log of B and C will be the same. Why other clients recieve this messages later than the original sender? By the way, on ubuntu 10.04/chrome all the motion is smooth. Two clients are launched in separated chromes. windows screenshot Can't post linux screenshot, need more than 10 reputation to post more hyperlinks. Listing of log, four clients simultaneously: [16:29:33.280858] 62.140.224.1 >> some data [16:29:33.280912] 87.249.9.98 << some data [16:29:33.280970] 87.249.9.98 << some data [16:29:33.281025] 87.249.9.98 << some data [16:29:33.281079] 62.140.224.1 << some data [16:29:33.323267] 62.140.224.1 >> some data [16:29:33.323326] 87.249.9.98 << some data [16:29:33.323386] 87.249.9.98 << some data [16:29:33.323440] 87.249.9.98 << some data [16:29:33.323493] 62.140.224.1 << some data [16:29:34.123435] 62.140.224.1 >> some data [16:29:34.123525] 87.249.9.98 << some data [16:29:34.123593] 87.249.9.98 << some data [16:29:34.123648] 87.249.9.98 << some data [16:29:34.123702] 62.140.224.1 << some data AS3 client code package { import adobe.utils.CustomActions; import flash.display.Sprite; import flash.events.DataEvent; import flash.events.Event; import flash.events.IOErrorEvent; import flash.events.KeyboardEvent; import flash.events.MouseEvent; import flash.events.SecurityErrorEvent; import flash.net.XMLSocket; import flash.system.Security; import flash.text.TextField; public class Main extends Sprite { private var socket :XMLSocket; private var textField :TextField = new TextField; private var connectButton :TextField = new TextField; public function Main():void { if (stage) init(); else addEventListener(Event.ADDED_TO_STAGE, init); } private function init(event:Event = null):void { socket = new XMLSocket(); socket.addEventListener(Event.CONNECT, connectHandler); socket.addEventListener(DataEvent.DATA, dataHandler); stage.addEventListener(KeyboardEvent.KEY_DOWN, keyDownHandler); addChild(textField); textField.y = 50; textField.width = 780; textField.height = 500; textField.border = true; connectButton.selectable = false; connectButton.border = true; connectButton.addEventListener(MouseEvent.MOUSE_DOWN, connectMouseDownHandler); connectButton.width = 105; connectButton.height = 20; connectButton.text = "click here to connect"; addChild(connectButton); } private function connectHandler(event:Event):void { textField.appendText("Connect\n"); textField.appendText("Press and hold any key\n"); } private function dataHandler(event:DataEvent):void { var now:Date = new Date(); textField.appendText(event.data + " time = " + now.getMinutes() + ":" + now.getSeconds() + ":" + now.getMilliseconds() + "\n"); connectButton.x += 2; } private function keyDownHandler(event:KeyboardEvent):void { socket.send("some data"); } private function connectMouseDownHandler(event:MouseEvent):void { var connectAddress:String = "ep1c.org"; var connectPort:Number = 13250; Security.loadPolicyFile("xmlsocket://" + connectAddress + ":" + String(connectPort)); socket.connect(connectAddress, connectPort); } } } Python server code from twisted.internet import reactor from twisted.internet.protocol import ServerFactory from twisted.protocols.basic import LineOnlyReceiver import datetime class EchoProtocol(LineOnlyReceiver): ##### name = "" id = 0 delimiter = chr(0) ##### def getName(self): return self.transport.getPeer().host def connectionMade(self): self.id = self.factory.getNextId() print "New connection from %s - id:%s" % (self.getName(), self.id) self.factory.clientProtocols[self.id] = self def connectionLost(self, reason): print "Lost connection from "+ self.getName() del self.factory.clientProtocols[self.id] self.factory.sendMessageToAllClients(self.getName() + " has disconnected.") def lineReceived(self, line): print "[%s] %s >> %s" % (datetime.datetime.now().time(), self, line) if line=="<policy-file-request/>": data = """<?xml version="1.0"?> <!DOCTYPE cross-domain-policy SYSTEM "http://www.adobe.com/xml/dtds/cross-domain-policy.dtd"> <!-- Policy file for xmlsocket://ep1c.org --> <cross-domain-policy> <allow-access-from domain="*" to-ports="%s" /> </cross-domain-policy>""" % PORT self.send(data) else: self.factory.sendMessageToAllClients( line ) def send(self, line): print "[%s] %s << %s" % (datetime.datetime.now().time(), self, line) if line: self.transport.write( str(line) + chr(0)) else: print "Nothing to send" def __str__(self): return self.getName() class ChatProtocolFactory(ServerFactory): protocol = EchoProtocol def __init__(self): self.clientProtocols = {} self.nextId = 0 def getNextId(self): id = self.nextId self.nextId += 1 return id def sendMessageToAllClients(self, msg): for client in self.clientProtocols: self.clientProtocols[client].send(msg) def sendMessageToClient(self, id, msg): self.clientProtocols[id].send(msg) PORT = 13250 print "Starting Server" factory = ChatProtocolFactory() reactor.listenTCP(PORT, factory) reactor.run()

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• Oracle's Customer Self-Service Solution Drives Value and Impacts Customers' Bottom Lines

  Cliff speaks with Scott Weinberg, Oracle's Director of Business Development, about Customer Self-Service and why it is an important business initiative. Learn the benefits of this solution and the unique aspects of Oracle's Customer Self-Service offerings.

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• Rhythmbox plugin code for hot key not working - why?

  - by Bunny Rabbit

  def activate(self,shell): self.shell = shell self.copy_selected() self.action = gtk.Action ('foo','bar','baz',None) self.activate_id = self.action.connect ('activate', self.call_bk_fn,self.shell) self.action_group = gtk.ActionGroup ('hot_key_action_group') self.action_group.add_action_with_accel (self.action, "<control>E") uim = shell.get_ui_manager () uim.insert_action_group (self.action_group, 0) uim.ensure_update () def call_bk_fn(): print('hello world') I am using the above code in a plugin for Rhythmbox and here I am trying to register the key Ctrl+E so that the call_bk_fn gets called whenever the key combination is pressed but its not working. Why is that so ?

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• Implementing touch-based rotation in cocoa touch

  - by ewoo

  I am wondering what is the best way to implement rotation-based dragging movements in my iPhone application. I have a UIView that I wish to rotate around its centre, when the users finger is touch the view and they move it. Think of it like a dial that needs to be adjusted with the finger. The basic question comes down to: 1) Should I remember the initial angle and transform when touchesBegan is called, and then every time touchesMoved is called apply a new transform to the view based on the current position of the finger, e.g., something like: - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { UITouch *touch = [touches anyObject]; CGPoint currentPoint = [touch locationInView:self]; //current position of touch if (([touch view] == self) && [Utility getDistance:currentPoint toPoint:self.middle] <= ROTATE_RADIUS //middle is centre of view && [Utility getDistance:currentPoint toPoint:self.middle] >= MOVE_RADIUS) { //will be rotation gesture //remember state of view at beginning of touch CGPoint top = CGPointMake(self.middle.x, 0); self.initialTouch = currentPoint; self.initialAngle = angleBetweenLines(self.middle, top, self.middle, currentPoint); self.initialTransform = self.transform; } } - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{ UITouch *touch = [touches anyObject]; CGPoint currentPoint = [touch locationInView:self]; //current position of touch if (([touch view] == self) && [Utility getDistance:currentPoint toPoint:self.middle] <= ROTATE_RADIUS && [Utility getDistance:currentPoint toPoint:self.middle] >= MOVE_RADIUS) { //a rotation gesture //rotate tile float newAngle = angleBetweenLines(self.middle, CGPointMake(self.middle.x, 0), self.middle, currentPoint); //touch angle float angleDif = newAngle - self.initialAngle; //work out dif between angle at beginning of touch and now. CGAffineTransform newTransform = CGAffineTransformRotate(self.initialTransform, angleDif); //create new transform self.transform = newTransform; //apply transform. } OR 2) Should I simply remember the last known position/angle, and rotate the view based on the difference in angle between that and now, e.g.,: - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { UITouch *touch = [touches anyObject]; CGPoint currentPoint = [touch locationInView:self]; //current position of touch if (([touch view] == self) && [Utility getDistance:currentPoint toPoint:self.middle] <= ROTATE_RADIUS && [Utility getDistance:currentPoint toPoint:self.middle] >= MOVE_RADIUS) { //will be rotation gesture //remember state of view at beginning of touch CGPoint top = CGPointMake(self.middle.x, 0); self.lastTouch = currentPoint; self.lastAngle = angleBetweenLines(self.middle, top, self.middle, currentPoint); } } - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{ UITouch *touch = [touches anyObject]; CGPoint currentPoint = [touch locationInView:self]; //current position of touch if (([touch view] == self) && [Utility getDistance:currentPoint toPoint:middle] <= ROTATE_RADIUS && [Utility getDistance:currentPoint toPoint:middle] >= MOVE_RADIUS) { //a rotation gesture //rotate tile float newAngle = angleBetweenLines(self.middle, CGPointMake(self.middle.x, 0), self.middle, currentPoint); //touch angle float angleDif = newAngle - self.lastAngle; //work out dif between angle at beginning of touch and now. CGAffineTransform newTransform = CGAffineTransformRotate(self.transform, angleDif); //create new transform self.transform = newTransform; //apply transform. self.lastTouch = currentPoint; self.lastAngle = newAngle; } The second option makes more sense to me, but it is not giving very pleasing results (jaggy updates and non-smooth rotations). Which way is best (if any), in terms of performance? Cheers!

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