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  • Python if statement efficiency

    - by Dennis
    A friend (fellow low skill level recreational python scripter) asked me to look over some code. I noticed that he had 7 separate statements that basically said. if ( a and b and c): do something the statements a,b,c all tested their equality or lack of to set values. As I looked at it I found that because of the nature of the tests, I could re-write the whole logic block into 2 branches that never went more than 3 deep and rarely got past the first level (making the most rare occurrence test out first). if a: if b: if c: else: if c: else: if b: if c: else: if c: To me, logically it seems like it should be faster if you are making less, simpler tests that fail faster and move on. My real questions are 1) When I say if and else, should the if be true, does the else get completely ignored? 2) In theory would if (a and b and c) take as much time as the three separate if statements would?

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  • How to configure SQLite db in Visual Studio

    - by ChrisC
    I've messed with Access a little bit in the past, had one class on OO theory, and one class on console c++ apps. Now, as a hobby project, I'm undertaking to write an actual app, which will be a database app using System.Data.SQLite and C#. I have the db's table structure planned. I have System.Data.SQLite installed and connected to VS Pro. I entered my tables and columns in VS, but that's where I'm stuck. I really don't know how to finish the db set up so I can start creating queries and testing the db structure. Can someone give me guidance to online resources that will help me learn how to get the db properly set up so I can proceed with testing it? I'm hoping for online resources specific to beginners using C# and System.Data.SQLite, but I'll use the closest I can get. Thanks.

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  • How to complie x64 asp.net website?

    - by Eran Betzalel
    I'm trying to compile (using Visual Studio) an ASP.Net website with the Chilkat library. The compilation fails due to this error: Could not load file or assembly 'ChilkatDotNet2, Version=9.0.8.0, Culture=neutral, PublicKeyToken=eb5fc1fc52ef09bd' or one of its dependencies. An attempt was made to load a program with an incorrect format. I've been told that this error occurs because of platform noncompliance. The weird thing is that although the compilation fails, the site works once accessed from a browser. My theory is that the IIS compilation uses csc.exe compiler from the Framework64 (64 bit) folder while the Visual Studio uses csc.exe compiler from the Framework (32 bit) folder. If this is acually it, how can I configure my Visual studio to run with the 64 bit compiler for ASP.Net sites? This is my current development configuration: Windows 7 (x64). Visual Studio 2008 Pro (x86 of course...). Chilkat library (x64) IIS/Asp.net (x64).

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  • Correct permutation cycle for Verhoeff algorithm

    - by James
    Hello, I'm implementing the Verhoeff algorithm for a check digit scheme, but there seems to be some disagreement in web sources as to which permutation cycle should form the basis of the permutation table. Wikipedia uses: (36)(01589427) while apparently, Numerical Recipies uses a different cycle and this book uses: (0)(14)(23)(56789), quoted from a 1990 article by Winters. It also notes that Verhoeff used the one Wikipedia quotes. Now, my number theory is a little rusty, but the Wikipedia cycle clearly will repeat after the 8th power, while the book one will take 10, despite it saying that s^8=s. Table 2.14(b) has other errors in the 2-cycles, so this is dubious anyway. Unfortunately, I don't have copies of the original articles (and am too tight to pay/disgusted that 40-year old knowledge is still being held to ransom by publishers), nor a copy of Numerical Recipes to check (and am loath to install their paranoia-induced copy protection plug-in to view online). So does any one know which is correct? Are they both correct?

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  • Different result with reverse proxy apache and lighttpd.

    - by Danny
    I have an Apache server running in reverse proxy mode in front of a Tomcat java server. It handle HTTP and HTTPS and send those request back and forth to the Tomcat server on an internal HTTP port. I'm trying to replace the reverse proxy with Lighttpd. Here's the problem: while asking for the same HTTPS url, while using Apache as the reverse proxy, the Tomcat server redirect (302) to an HTTPS page but with Lighttpd it redirect to the same page in HTTP (not HTTPS). What does Lighttpd could do different in order to have a different result from the backend server? In theory, using Apache or Lighttpd server as a reverse proxy should not change anything... but it does. Any idea? I'll try to find something by sniffing the traffic on the backend tomcat server.

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  • mysql, sqlite database source code

    - by Yang
    hi guys, i know implementing database is a huge topic, but i want to have a basic understanding of how database systems works (e.g. memory management, binary tree, transaction, sql parsing, multi-threading, partitions, etc) by investigating the source code of the database, since there are a few already proven very robust open source databases like mysql, sqlite and so on. however, the code are very complicated and i have no clue where to start. also i find that the old school database textbooks are only explaining the theory, not the implementation details. Can anyone suggest how should i get started and is there any books that emphasis on the technology and techniques of building dbms used in modern database industry? Thank in advance!

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  • Determining the hostname/IP address from the MX record in PHP

    - by pmmenneg
    Hi there, have a basic email domain validation script that takes a user's email domain, resolves the IP address from that and then checks that against various published blacklists. Here is how I am determining the IP: $domain = substr(strchr($email, '@'), 1); $ip = gethostbyname($domain); The problem is that some email address domains, such as [email protected], use an MX record rather than an A record, so using gethostbyname('alumni.example.net') will fail to resolve. I know when a user's email is using an MX in the email itself by using the PHP checkdnsrr function, but once at that stage am a little stuck as to how to proceed. In theory, I could parse out the 'root' domain, i.e. 'example.net' and check it, but I've not found reliable regex that can handle this task when the user could easily have an email the format of [email protected]... So, any suggestions on how to best tackle this??

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  • Using AChartEngine library for graphs, not able to get value for diffrent x-axis value

    - by kundan Chaudhary
    public static ArrayList<double[]> Value = new ArrayList<double[]>(); private double[] x = new double[10]; private double[] y = new double[10]; int counter = -1; add.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { counter++; x[counter] = Double.parseDouble(income_1.getText().toString()); y[counter] = Double.parseDouble(income_2.getText().toString()); income_1.setText(""); income_2.setText(""); } }); publish.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { if (Value != null) { Value.add(x); Value.add(y); Intent intent = salesStackedBarChart.execute(BarChart.this, Value, counter); startActivity(intent); } } }); //and in SalesStackedBarChart.java class public Intent execute(Context context, ArrayList<double[]> values ,int counter) { int count = counter + 1; double fcount = counter + 1.5; String[] titles = new String[] { "Android", "iPhone" }; int[] colors = new int[] { Color.GREEN, Color.CYAN }; XYMultipleSeriesRenderer renderer = buildBarRenderer(colors); setChartSettings(renderer, "Yearly revenue in the last "+count+" years", "Years", "revenue in $", 0.5, fcount, 0, 24000, Color.GRAY, Color.LTGRAY); renderer.setXLabels(count); renderer.setYLabels(10); renderer.setDisplayChartValues(true); renderer.setXLabelsAlign(Align.LEFT); renderer.setYLabelsAlign(Align.LEFT); renderer.setZoomRate(1.1f); renderer.setBarSpacing(0.5); return ChartFactory.getBarChartIntent(context, buildBarDataset(titles, values), renderer, Type.DEFAULT); } // in AbstractDemoChart.java class protected XYMultipleSeriesDataset buildBarDataset(String[] titles, List<double[]> values) { XYMultipleSeriesDataset dataset = new XYMultipleSeriesDataset(); int length = titles.length; for (int i = 0; i < length; i++) { CategorySeries series = new CategorySeries(titles[i]); double[] v = values.get(i); int seriesLength = v.length; for (int k = 0; k < seriesLength; k++) { series.add(v[k]); } dataset.addSeries(series.toXYSeries()); } return dataset; } Run this project i get graph with x- axis value: 1,2,3,4,5.... But I want to print value: 2005,2006,2007,2008..... I changed in some code like: setChartSettings(renderer, "Yearly revenue in the last "+count+" years", "Years", "revenue in $", 2005, 2010, 0, 24000, Color.GRAY, Color.LTGRAY); and run project i get value of x-axis like: 2005,2006,2007.... but not get graph bar value. Values of all x-axis are null. How can I make this work?

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  • Which is faster in Python: x**.5 or math.sqrt(x)?

    - by Casey
    I've been wondering this for some time. As the title say, which is faster, the actual function or simply raising to the half power? UPDATE This is not a matter of premature optimization. This is simply a question of how the underlying code actually works. What is the theory of how Python code works? I sent Guido van Rossum an email cause I really wanted to know the differences in these methods. My email: There are at least 3 ways to do a square root in Python: math.sqrt, the '**' operator and pow(x,.5). I'm just curious as to the differences in the implementation of each of these. When it comes to efficiency which is better? His response: pow and ** are equivalent; math.sqrt doesn't work for complex numbers, and links to the C sqrt() function. As to which one is faster, I have no idea...

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  • Can I use ido-completing-read instead of completing-read everywhere?

    - by haxney
    I'm a big fan of ido-mode, so much so that I would like to use it for things like describe-function or find-tag and so on, without having to write something like in "Can I get ido-mode-style completion for searching tags in Emacs?" for each one. Both (defalias completing-read ido-completing-read) and (setf 'completing-read 'ido-completing-read) don't work, at least partly because ido-completing-read calls completing-read in its body, so any simple redefinition would result in infinite recursion. In theory, it should be possible, since the first line of the docstring for ido-completing-read is "Ido replacement for the built-in completing-read." I've looked around a bit and can't seem to find anyone else who has attempted or succeeded at it. I realize that Icicles [2] probably provides something like this, and I may end up going with that anyway, but it is a bit more of a plunge than I care to take right now. Thanks for any help.

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  • Event based scheduling in excel

    - by andreas
    Hey fellas! Where i am working we have a number of contractor programmers. We handle the requirements and the project management of our products. I have been trying using various project timing and estimations techniques but cant get the hang of it yet. I have read Joel's evidence based scheduling and i was wondering if there's anything out there that can help me apply that theory? not looking for complex software but perhaps something in excel? Any help will be appreciated Andreas

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  • Event based PROJECT MANAGEMENT

    - by andreas
    Hey fellas! Where i am working we have a number of contractor programmers. We handle the requirements and the project management of our products. I have been trying using various project timing and estimations techniques but cant get the hang of it yet. I have read Joel's evidence based scheduling and i was wondering if there's anything out there that can help me apply that theory? not looking for complex software but perhaps something in excel? Any help will be appreciated Andreas

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  • Interview questions for junior C and C++ developer position

    - by Ondrej Slinták
    What interview questions should people expect as a junior C and C++ developer? Code questions or more of theory? Solutions in pseudo-code or in C code? Maybe I'm misinterpreting the word "junior", but I have no idea what would anyone ask me if I have no C work experiences. I'm bit afraid of tricky questions with pointers, so I'd like to be sure what should I look up before actually going there. I'm a junior PHP developer with 1 year of experiences, if it helps the question. Hope it isn't duplicate as I'm asking particularly about junior developer job.

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  • Small web-framework like Sinatra, Ramaze etc in .NET

    - by Christian W
    Are there any similar frameworks like Sinatra, Ramaze etc in .NET? I'm in theory after a framework that let's me create an entire webapp with just one classfile (conceptually) like Sinatra. I'm going to use it for something work-internal, where ASP.NET MVC is too "big" (and I get confused by it's usage) and I have WebForms up to my ears right now (doing a big webforms based project, currently hating it ;) ) Any suggestions? Oh, and I need to be able to host it in IIS. I would go for IronRuby with Sinatra, but I can't find a step-by-step tut for setting it up in IIS ;)

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  • Good implementations of reinforced learning?

    - by Paperino
    For an ai-class project I need to implement a reinforcement learning algorithm which beats a simple game of tetris. The game is written in Java and we have the source code. I know the basics of reinforcement learning theory but was wondering if anyone in the SO community had hands on experience with this type of thing. What would your recommended readings be for an implementation of reinforced learning in a tetris game? Are there any good open source projects that accomplish similar things that would be worth checking out? Thanks in advanced Edit: The more specific the better, but general resources about the subject are welcomed. Follow up: Thought it would be nice if I posted a followup. Here's the solution (code and writeup) I ended up with for any future students :). Paper / Code

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  • 2d terrain generation in real time

    - by Skoder
    Hey, I'm trying to create a game similar to this (Note:When you click 'play', there are SFX in the game which you can't seem to turn off, so you may want to check volume). In particular, I'm interested in knowing how the 'infinite' landscape is generated. Are there any tutorials/articles describing this? I came across procedural generation, but I'm not quite sure what topics I should be looking for (or if it's even procedural generation). (I'm using C#, but I don't mind the language as I assume the theory behind it remains the same) Thanks for any suggestions

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  • WPF UC in Winforms occasionally has an odd border to the left / visually corrupted

    - by Ryan ONeill
    I have a WPF user control I created that is used to show the state of tasks in my UI. I get the odd report back that the control sometimes has a nasty looking border to the left and I cannot reproduce it. The control looks like this (when working) (grey tick=not run, green=OK,red cross=fail,hourglass=running); It looks like this when the problem occurs; It may have something to do with the layering of those icons, when the state changes the others are made invisible and the relevant icon is made visible. The four icons are all stacked on top of each other. It could also be the background in theory, which I'll look at next. Problem is reported on both flat panel and CRT displays. Any guidance greatly appreciated. Update: 1) SnapsToDevicePixels does not affect the issue. 2) Grid is not used, only a canvas.

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  • Are these AVAudioSettings right?

    - by Dyldo42
    self.recordSettings = [NSMutableDictionary dictionary]; [recordSettings setValue:[NSNumber numberWithInt:kAudioFormatAppleIMA4] forKey:AVFormatIDKey]; [recordSettings setValue:[NSNumber numberWithFloat:44100.0] forKey:AVSampleRateKey]; [recordSettings setValue:[NSNumber numberWithInt:1] forKey:AVNumberOfChannelsKey]; recordSettings is declared in my view's header file and initialised in its viewDidLoad method. For some reason, everything is working in the simulator, but on a device, the [recorder record] method is returning NO. The only theory I have is that something in the recordSettings isn't compatible with an actual device. Any ideas?

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  • MySQl Error #1064

    - by 01010011
    Hi, I keep getting this error: MySQL said: #1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'INSERT INTO books.book(isbn10,isbn13,title,edition,author_f_name,author_m_na' at line 15 with this query: USE books; DROP TABLE IF EXISTS book; CREATE TABLE `books`.`book`( `book_id` INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY, `isbn10` VARCHAR(15) NOT NULL, `isbn13` VARCHAR(15) NOT NULL, `title` VARCHAR(50) NOT NULL, `edition` VARCHAR(50) NOT NULL, `author_f_name` VARCHAR(50) NOT NULL, `author_m_name` VARCHAR(50) NOT NULL, `author_l_name` VARCHAR(50) NOT NULL, `cond` ENUM('as new','very good','good','fair','poor') NOT NULL, `price` DECIMAL(8,2) NOT NULL, `genre` VARCHAR(50) NOT NULL, `quantity` INT NOT NULL) INSERT INTO books.book(isbn10,isbn13,title,edition,author_f_name,author_m_name,author_l_name,cond,price,genre,quantity)** VALUES ('0136061699','978-0136061694','Software Engineering: Theory and Practice','4','Shari','Lawrence','Pfleeger','very good','50','Computing','2'); Any idea what the problem is?

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  • SSD and programming

    - by Simon Johnson
    I'm trying to put together a business case for getting every developer in our company an Intel SSD drive. The main codebase contains roughly 400,000 lines of code. My theory is that since the code is scattered about in maybe 1500 files, an SSD drive would be substantially faster for compiles. The logic being that many small reads really punishes the seak-time bottle-neck of a traditional hard-drive. Am I right? Is SSD worth the money in productivity gains by reducing the edit/compile cycle time?

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  • Slow SQLite access on iPhone

    - by georgij
    I have a quite slow data retrieval from a sqlite database on my iPhone and perhaps someone have an alternative idea to explain this. From what I tracked down so far sqlite3_step(statement) is sometimes unusually slow. While retrieving e.g. 50 rows from the database to execute this step takes normally some milliseconds but sometimes it takes several seconds. My database is not small (80MB) and my theory is that the reason is paging. But can someone else think of an other reason for this?

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  • How would I / could I obtain an reasonably comprehensive list of domain names?

    - by Simon
    I know that domain names are constantly changing, and I know there are a lot of them, but there is clearly a region of the domain name space which is stable. How would I go about getting a list, even a very big one? Such a thing must logically exist, even if it is in a distributed form, because the web's DNS servers resolve names to IP addresses. So in theory if I could poll all the DNS servers in the world at a moment in time I would have the complete list of mapped names. Is there a practical way of doing that? As an aside, does anyone have any good estimates of how many domain names exist at the moment?

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  • Master's in Software Engineering vs. Master's in Computer Science: which degree is preferred by empl

    - by dbarker
    I've been building software professionally for 7 years and am considering a master's degree. I understand the difference between these two degrees as simply: MSCS is the theory while MSE is the practice. I'm equally interested in both and would be happy with either, although I'm curious how these degrees rank in the eyes of a potential employer. I could see two views that a hiring manager could possibly take: a MSCS is loftier and has an implied knowledge of Software Engineering an MSE is more practical and has an implied knowledge of Computer Science In my own experience I've seen both MSCS degree holders than cannot program at all while others are among the best programmers I've met, so of course actual ability will depend on the individual. My question is about the "on paper" value of these two degrees when seeking a job. All things considered, is one degree more hirable, higher-paying than the other?

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  • Broadcast-style Bluetooth using Sockets on the iPhone?

    - by Kyle
    Is there any way to open a broadcast bluetooth socket, take a listen and send replies? I want a proper peer to peer system where I broadcast and listen for broadcasts in an area. That way, variable clients can mingle. Is this possible? My theory is this: If GameKit can sit around wasting 25 seconds of the users time whilst having access to a broadcast socket, can't I? Or, must I be in kernel mode for such access? I'm not really sure where the proper bluetooth headers are as well. Thanks for reading!

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  • Is it possible for competing file access to cause deadlock in Java?

    - by BlairHippo
    I'm chasing a production bug that's intermittent enough to be a real bastich to diagnose properly but frequent enough to be a legitimate nuisance for our customers. While I'm waiting for it to happen again on a machine set to spam the logfile with trace output, I'm trying to come up with a theory on what it could be. Is there any way for competing file read/writes to create what amounts to a deadlock condition? For instance, let's say I have Thread A that occasionally writes to config.xml, and Thread B that occasionally reads from it. Is there a set of circumstances that would cause Thread B to prevent Thread A from proceeding? My thanks in advance to anybody who helps with this theoretical fishing expedition. Edit: To answer Pyrolistical's questions: the code isn't using Filelock, and is running on a WinXP machine.

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