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• Please recommend good books for telemetry / SCADA system design & programming

  - by Mawg

  I am looking at several projects, all with roughly the same fucntionality. Some instruments collect some data (or control some functionality). They commmunicate by Internet (Etehrnet/wifi/GPRS/sasatellite) with a databse server which stores the measurements and provides a browser based means of qeurying the data, prodcuing reports, etc (and possibly also allows control of the remote equipment). Can anyone recommend a good book describing an approach to developing such a software architecture, keeping it generic, which tools, languages. test methods, etc to use? (note to self: ask a similar question about possible existing frameworks)

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• database design suggesion

  - by Bharanikumar

  Hi , am going to start new travel site, I want some advise from guru's regarding database design , Things coming to picture are, Book taxi online , This is the core idea, So i like to implement lot of jquery,ajax stuff in my site , Main thing site must run veryt fast,safe,security, In mysql , which typw shall i use, MYISAM OR INNODB Which is best type for ajax works, fast,safe ,secure ,performance view . This is my demo site, Just look this site, i implemented some ajax stuff here, my-url In this site please choose the postcode in the taxifrom tab, It ask you value please enter, just enter nw7 , See How long it will take for response,some time no response and system goes to hang or idle mode, Also please look the diversion , select No diversion, There you will list of textbox, enter the nw3 then hit the search icon , See after 80seconds only , you will get response from DB, See this too bad response ... This is DB , my Database type if myisam ,no idexing , no fulltext and nothing...no constraints, So please advise me , which database type i choose, Myisam or innodb, Thanks Bharanikumar

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• Is block style really this important?

  - by Jack Roscoe

  I just watched a video of Douglas Crockford's presentation about his 2009 book JavaScript: The Good Parts. In the video, he explains that the following block is dangerous because it produces silent errors: return { ok: false }; And that it should actually be written like this (emphasising that although seemingly identical the behavioural difference is crucial): return { ok: false }; You can see his comments around 32 minutes into the video here: http://www.youtube.com/watch?v=hQVTIJBZook&feature=player_embedded#!&start=1920 I have not heard this before, and was wondering if this rule still applies or if this requirement in syntax has been overcome by JavaScript developments since this statement was made. I found this very interesting as I have NOT been writing my code this way, and wanted to check that this information was not out of date.

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• Is Pex (Test generation) really usefull tool?

  - by Yauheni Sivukha

  Yes, it is possible to generate tests on boundary values for functions like "Sum" or "Divide". Pex is a good tool here. But more often we create tests on business behaviour. Let's consider example from classic Beck's tdd book: [Test] public void ShouldRoundOnCreation() { Money money = new Money(20.678); Assert.AreEqual(20.68,money.Amount); Assert.AreEqual(2068,money.Cents); } Can this test be generated? No :) 95 % of tests in my projects check business logic, and can not be generated. Pex (Especially in pair with Moles) can give 100% code coverage, but a high code coverage rate of a test suite does never indicate, that code is well tested - It only gives false confidence that everything is tested. And this is very dangerous. So, the question is - Is Pex really usefull tool?

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• GroupLayout giving error with java swing

  - by Name

  I am getting some long list of error . Can anyone suggest me where i am wrong with group layout layout.setHorizontalGroup( layout.createSequentialGroup() .addComponent(new JLabel("Enter Book Name")) .addComponent(new JTextField("TextField", 20)) ); ERROR Exception in thread "main" java.lang.IllegalStateException: javax.swing.JTextField[,0,0,0x0,invalid,layout=javax.swing.plaf.basic.BasicTextUI$UpdateHandler,alignmentX=0.0,alignmentY=0.0,border=javax.swing.plaf.BorderUIResource$CompoundBorderUIResource@3d0bbf9e,flags=296,maximumSize=,minimumSize=,preferredSize=,caretColor=sun.swing.PrintColorUIResource[r=51,g=51,b=51],disabledTextColor=javax.swing.plaf.ColorUIResource[r=184,g=207,b=229],editable=true,margin=javax.swing.plaf.InsetsUIResource[top=0,left=0,bottom=0,right=0],selectedTextColor=sun.swing.PrintColorUIResource[r=51,g=51,b=51],selectionColor=javax.swing.plaf.ColorUIResource[r=184,g=207,b=229],columns=20,columnWidth=0,command=,horizontalAlignment=LEADING] is not attached to a vertical group at javax.swing.GroupLayout.checkComponents(Unknown Source) at javax.swing.GroupLayout.prepare(Unknown Source)

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• imagebutton alternative text doesn't appear in chrome

  - by salamonti

  image button alternative text doesn't appear in chrome browser this is html button code <div class="bookoffer"> <table class="headertable" style="padding-bottom: 0px; height: 100%;"> <tr> <td class="bookbt"> <asp:ImageButton AlternateText="Book" CssClass="bookstyle" ID="ImageButton1" runat="server" CommandArgument='<%# Eval("OfferID") %>' OnCommand="ImageButton1_Command" /> </td> </tr> </table> </div> why alternative text doesn't appear ?

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• float change from python 3.0.1 to 3.1.2

  - by Jeremy

  Im trying to learn python. I am using 3.1.2 and the o'reilly book is using 3.0.1 here is my code import urllib.request price = (99.99) while price 4.74: page = urllib.request.urlopen ("http://www.beans-r-us.biz/prices-loyalty.html") text = page.read().decode("utf8") where = text.find('>$') start_of_price = where + 2 end_of_price = start_of_price + 6 price = float(text[start_of_price:end_of_price]) print ("Buy!") - here is my error Traceback (most recent call last): File "/Users/odin/Desktop/Coffe.py", line 14, in price = float(text[start_of_price:end_of_price]) ValueError: invalid literal for float(): 4.59 what is wrong? please help!!

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• What does setting the GL color before doing a texture mapping operation do?

  - by quixoto

  I am looking at some sample code in a book that creates a jittered antialiasing effect by repeatedly rendering a scene (at different offsets) onto a offscreen texture, then using that texture to repeatedly draw a quad in the main view with some blend stuff set up. To accumulate the color "correctly", the code is setting the color like so: glColor4f(f, f, f, 1); where f is 1.0/number_of_samples, and then binding the offscreen texture and rendering it. Since textures come with their own color and alpha data, what is the effect (mathematically and intuitively) that setting the overall "color" in advance achieves? Thanks.

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• Help me find some good 'Reflection' reading materials??

  - by IbrarMumtaz

  If it wasn't you guys I would've never discovered Albahari.com's free threading ebook. My apologies if I come off as being extremely lazy but I need to make efficient use of my time and make sure am not just swallowing any garbage of the web. Therefore I am looking for the best and most informative and with a fair bit of detail for the Reflection chapter in .Net. Reflection is something that comes up time and time again and I want to extend my reading from what I know already from the official 70-536 book. I'm not a big fan of MSDN but at the moment that's al I'm using. Anyone got any other good published reading material off the inter web that can help revision for the entrance exam??? Would be greatly appreciated !!! Thanks in Advance, Ibrar

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• Which edition of windows internals should I read?

  - by pecker

  Hello, I want to get into windows driver development. I heard from the community that before diving into driver development one must be familiar with windows internals that means one must read "Windows Internals by Mark Russinovich. I'm going to buy this book today. Which edtition should I buy? 4th edition covers Windows XP & Windows 2003 where as 5th edition covers Windows Vista & windows server 2008. I don't know in driver world how much difference this thing would make. How different are these two editions? should I first read 4th edition & then come to 5th or should I directly dive into 5th?

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• Atoms and references

  - by StackedCrooked

  According to the book Programming Clojure refs manage coordinated, synchronous changes to shared state and atoms manage uncoordinated, synchronous changes to shared state. If I understood correctly "coordinated" implies multiple changes are encapsulated as one atomic operation. If that is the case then it seems to me that coordination only requires using a dosync call. For example what is the difference between: (def i (atom 0)) (def j (atom 0)) (dosync (swap! i inc) (swap! j dec)) and: (def i (ref 0)) (def j (ref 0)) (dosync (alter i inc) (alter j dec))

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• Git: What is a tracking branch?

  - by jerhinesmith

  Can someone explain a "tracking branch" as it applies to git? Here's the definition from git-scm.com: A 'tracking branch' in Git is a local branch that is connected to a remote branch. When you push and pull on that branch, it automatically pushes and pulls to the remote branch that it is connected with. Use this if you always pull from the same upstream branch into the new branch, and if you don't want to use "git pull" explicitly. Unfortunately, being new to git and coming from SVN, that definition makes absolutely no sense to me. I'm reading through "The Pragmatic Guide to Git" (great book, by the way), and they seem to suggest that tracking branches are a good thing and that after creating your first remote (origin, in this case), you should set up your master branch to be a tracking branch, but it unfortunately doesn't cover why a tracking branch is a good thing or what benefits you get by setting up your master branch to be a tracking branch of your origin repository. Can someone please enlighten me (in English)?

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• discover if mod_rewrite is working (MAMP + codeigniter)

  - by Patrick

  Hi, I'm experimenting (and having problems!) with codeigniter. In particular, links do not work. even if they are correct (eg. http://localhost/ci-book/welcome/cat/3, where welcome is controller, cat the method), they can't be open and chrome says "Oops! This link appears to be broken...." Someone suggested to check that mod_rewrite is working. How can I do that? I'm using Mamp. thanks, P.

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• Why isn't the "this." command needed in this constructor? (java)

  - by David

  I'm reading a book about java. It just got to explaining how you create a class called "deck" which contains an array of cards as its instance variable(s). Here is the code snippit: class Deck { Card[] cards; public Deck (int n) { cards = new Card[n]; } } why isn't the this. command used? for example why isn't the code this: class Deck { Card[[] cards; public Deck (int n) { this.cards = new Card[n]; } }

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• Books on OpenGL ES targeted towards the iPhone

  - by Frank V

  There are a few posts on this site about OpenGL and the iPhone. Some even on books but I think you'll find this question is a bit different. I've searched and searched and have come to the conclusion that there are currently no books that specifically cover OpenGL ES on the iPhone platform. There are books that cover OpenGL ES [2.0] (note: the linked book covers OpenGL ES 2.0 but the iPhone uses OpenGL ES 1.1 which, I understand, is not backward compatible)... but they only have a small section for the iPhone (if any). What I want to know, is if anybody knows of any books that are forthcoming that specifically cover OpenGL ES 1.1 on the iPhone?

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• Ad hoc network between iPhone and non iPhone devices???

  - by gn-mithun

  Is it possible to set up a ad hoc network between an iPhone and a totally different device like camera,scanner or printer and build a data tunnel between them to exchange data or services. I believe iPhone does not have the provision of creating an ad hoc network. So i am assuming that the other device are the initiator of the ad hoc network. I tried doing the same with a mac book and iPhone and i could surf on the phone after enabling internet sharing. But i wanted to make sure that its possible with other devices as well I believe the upcoming WiFi Direct is a way to do it.

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• Objective C for Windows

  - by Luther Baker

  What would be the best way to write Objective-C on the Windows platform? Cygwin and gcc? Is there a way I can somehow integrate this into Visual Studio? Along those lines - are there any suggestions as to how to link in and use the Windows SDK for something like this. Its a different beast but I know I can write assembly and link in the Windows DLLs giving me accessibility to those calls but I don't know how to do this without googling and getting piecemeal directions. Is anyone aware of a good online or book resource to do or explain these kinds of things?

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• Help Forming An SQL Query That Selects The Max Difference Of Two Fields

  - by Frank

  I'm trying to select a record with the most effective votes. Each record has an id, the number of upvotes (int) and the number of downvotes (int) in a MySQL database. I know basic update, select, insert queries but I'm unsure of how to form a query that looks something like: SELECT * FROM topics WHERE MAX(topic.upvotes - topic.downvotes). Please excuse my made up SQL. The tutorials on SQL I find on the internet cover very basic stuff. Does anyone recommend a good book on this subject?

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• Using Rails and Rspec, how do you test that the database is not touched by a method

  - by Will Tomlins

  So I'm writing a test for a method which for performance reasons should achieve what it needs to achieve without using SQL queries. I'm thinking all I need to know is what to stub: describe SomeModel do describe 'a_getter_method' do it 'should not touch the database' do thing = SomeModel.create something_inside_rails.should_not_receive(:a_method_querying_the_database) thing.a_getter_method end end end EDIT: to provide a more specific example: class Publication << ActiveRecord::Base end class Book << Publication end class Magazine << Publication end class Student << ActiveRecord::Base has_many :publications def publications_of_type(type) #this is the method I am trying to test. #The test should show that when I do the following, the database is queried. self.publications.find_all_by_type(type) end end describe Student do describe "publications_of_type" do it 'should not touch the database' do Student.create() student = Student.first(:include => :publications) #the publications relationship is already loaded, so no need to touch the DB lambda { student.publications_of_type(:magazine) }.should_not touch_the_database end end end So the test should fail in this example, because the rails 'find_all_by' method relies on SQL.

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• Why are difference lists more efficient than regular concatenation?

  - by Craig Innes

  I am currently working my way through the Learn you a haskell book online, and have come to a chapter where the author is explaining that some list concatenations can be ineffiecient: For example ((((a ++ b) ++ c) ++ d) ++ e) ++ f Is supposedly inefficient. The solution the author comes up with is to use 'difference lists' defined as newtype DiffList a = DiffList {getDiffList :: [a] -> [a] } instance Monoid (DiffList a) where mempty = DiffList (\xs -> [] ++ xs) (DiffList f) `mappend` (DiffList g) = DiffList (\xs -> f (g xs)) I am struggling to understand why DiffList is more computationally efficient than a simple concatenation in some cases. Could someone explain to me in simple terms why the above example is so inefficient, and in what way the DiffList solves this problem?

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• n-grams from text in PostgreSQL

  - by harshsinghal

  I am looking to create n-grams from text column in PostgreSQL. I currently split(on white-space) data(sentences) in a text column to an array. select regexp_split_to_array(sentenceData,E'\s+') from tableName Once I have this array, how do I go about: Creating a loop to find n-grams, and write each to a row in another table Using unnest I can obtain all the elements of all the arrays on separate rows, and maybe I can then think of a way to get n-grams from a single column, but I'd loose the sentence boundaries which I wise to preserve. Sample SQL code for PostgreSQL to emulate the above scenario create table tableName(sentenceData text); INSERT INTO tableName(sentenceData) VALUES('This is a long sentence'); INSERT INTO tableName(sentenceData) VALUES('I am currently doing grammar, hitting this monster book btw!'); INSERT INTO tableName(sentenceData) VALUES('Just tonnes of grammar, problem is I bought it in TAIWAN, and so there aint any englihs, just chinese and japanese'); select regexp_split_to_array(sentenceData,E'\s+') from tableName; select unnest(regexp_split_to_array(sentenceData,E'\s+')) from tableName;

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• Measuring the performance of classification algorithm

  - by Silver Dragon

  I've got a classification problem in my hand, which I'd like to address with a machine learning algorithm ( Bayes, or Markovian probably, the question is independent on the classifier to be used). Given a number of training instances, I'm looking for a way to measure the performance of an implemented classificator, with taking data overfitting problem into account. That is: given N[1..100] training samples, if I run the training algorithm on every one of the samples, and use this very same samples to measure fitness, it might stuck into a data overfitting problem -the classifier will know the exact answers for the training instances, without having much predictive power, rendering the fitness results useless. An obvious solution would be seperating the hand-tagged samples into training, and test samples; and I'd like to learn about methods selecting the statistically significant samples for training. White papers, book pointers, and PDFs much appreciated!

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• stored procedures and triggers the same in sql server than mysql?

  - by user314877

  Hello, I have two stored procedures and one trigger for a class I am taking that are done in sql server 2005. I want to recreate them in mysql with phpmyadmin. Everytime i put them in I get a 1064 error. Is this becuase phpmyadmin does not handle stored procedures or triggers well, or is it becuase the syntax from sql server 2005 to mysql is very different? If it is this, then where could i go online to learn the correct syntax to write my stored procedures and triggers in mysql/phpmyadmin... or should I just pick up a book at barnes and nobles? This is my senior project.

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• Why does my submit button fail to trigger Javascript MVC?

  - by user54197

  I have a simple code from a book and the code should display data from my controller in the "results" span. What am I missing? <asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server"> <script type="text/javascript"> $("form[action$='GetQuote']").submit(function() { $.post($(this).attr("action"), $(this).serialize(), function(response) { $("#results").html(response); }); return false; }); </script> <h2>Index</h2> <%using (Html.BeginForm("GetQuote","Stocks")) { %> Symbol: <%= Html.TextBox("symbol") %> <input type="submit" /> <span id="results"></span> <% } %> <p><i><%=DateTime.Now.ToLongTimeString() %></i></p> </asp:Content>

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• What would you do if you coded a C++/OO cross-platform framework and realize its laying on your disk

  - by Manuel

  This project started as a development platform because i wanted to be able to write games for mobile devices, but also being able to run and debug the code on my desktop machine too (ie, the EPOC device emulator was so bad): the platforms it currently supports are: Window-desktop WinCE Symbian iPhone The architecture it's quite complete with 16bit 565 video framebuffer, blitters, basic raster ops, software pixel shaders, audio mixer with shaders (dsp fx), basic input, a simple virtual file system... although this thing is at it's first write and so there are places where some refactoring would be needed. Everything has been abstracted away and the guiding principle are: mostly clean code, as if it was a book to just be read object-orientation, without sacrifying performances mobile centric The idea was to open source it, but without being able to manage it, i doubt the software itself would benefit from this move.. Nevertheless, i myself have learned a lot from unmaintained projects. So, thanking you in advance for reading all this... really, what would you do?

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