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• HLSL, Program pixel shader with different Texture2D downscaling algorithms

  - by Kaminari

  I'm trying to port some image interpolation algorithms into HLSL code, for now i got: float2 texSize; float scale; int method; sampler TextureSampler : register(s0); float4 PixelShader(float4 color : COLOR0, float2 texCoord : TEXCOORD0) : COLOR0 { float2 newTexSize = texSize * scale; float4 tex2; if(texCoord[0] * texSize[0] > newTexSize[0] || texCoord[1] * texSize[1] > newTexSize[1]) { tex2 = float4( 0, 0, 0, 0 ); } else { if (method == 0) { tex2 = tex2D(TextureSampler, float2(texCoord[0]/scale, texCoord[1]/scale)); } else { float2 step = float2(1/texSize[0], 1/texSize[1]); float4 px1 = tex2D(TextureSampler, float2(texCoord[0]/scale-step[0], texCoord[1]/scale-step[1])); float4 px2 = tex2D(TextureSampler, float2(texCoord[0]/scale , texCoord[1]/scale-step[1])); float4 px3 = tex2D(TextureSampler, float2(texCoord[0]/scale+step[0], texCoord[1]/scale-step[1])); float4 px4 = tex2D(TextureSampler, float2(texCoord[0]/scale-step[0], texCoord[1]/scale )); float4 px5 = tex2D(TextureSampler, float2(texCoord[0]/scale+step[0], texCoord[1]/scale )); float4 px6 = tex2D(TextureSampler, float2(texCoord[0]/scale-step[0], texCoord[1]/scale+step[1])); float4 px7 = tex2D(TextureSampler, float2(texCoord[0]/scale , texCoord[1]/scale+step[1])); float4 px8 = tex2D(TextureSampler, float2(texCoord[0]/scale+step[0], texCoord[1]/scale+step[1])); tex2 = (px1+px2+px3+px4+px5+px6+px7+px8)/8; tex2.a = 1; } } return tex2; } technique Resample { pass Pass1 { PixelShader = compile ps_2_0 PixelShader(); } } The problem is that programming pixel shader requires different approach because we don't have the control of current position, only the 'inner' part of actual loop through pixels. I've been googling for about whole day and found none open source library with scaling algoriths used in loop. Is there such library from wich i could port some methods? I found http://www.codeproject.com/KB/GDI-plus/imgresizoutperfgdiplus.aspx but I really don't understand His approach to the problem, and porting it will be a pain in the ... Wikipedia tells a matematic approach. So my question is: Where can I find easy-to-port graphic open source library wich includes simple scaling algorithms? Of course if such library even exists :)

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• What's the best name for a non-mutating "add" method on an immutable collection?

  - by Jon Skeet

  Sorry for the waffly title - if I could come up with a concise title, I wouldn't have to ask the question. Suppose I have an immutable list type. It has an operation Foo(x) which returns a new immutable list with the specified argument as an extra element at the end. So to build up a list of strings with values "Hello", "immutable", "world" you could write: var empty = new ImmutableList<string>(); var list1 = empty.Foo("Hello"); var list2 = list1.Foo("immutable"); var list3 = list2.Foo("word"); (This is C# code, and I'm most interested in a C# suggestion if you feel the language is important. It's not fundamentally a language question, but the idioms of the language may be important.) The important thing is that the existing lists are not altered by Foo - so empty.Count would still return 0. Another (more idiomatic) way of getting to the end result would be: var list = new ImmutableList<string>().Foo("Hello"); .Foo("immutable"); .Foo("word"); My question is: what's the best name for Foo? EDIT 3: As I reveal later on, the name of the type might not actually be ImmutableList<T>, which makes the position clear. Imagine instead that it's TestSuite and that it's immutable because the whole of the framework it's a part of is immutable... (End of edit 3) Options I've come up with so far: Add: common in .NET, but implies mutation of the original list Cons: I believe this is the normal name in functional languages, but meaningless to those without experience in such languages Plus: my favourite so far, it doesn't imply mutation to me. Apparently this is also used in Haskell but with slightly different expectations (a Haskell programmer might expect it to add two lists together rather than adding a single value to the other list). With: consistent with some other immutable conventions, but doesn't have quite the same "additionness" to it IMO. And: not very descriptive. Operator overload for + : I really don't like this much; I generally think operators should only be applied to lower level types. I'm willing to be persuaded though! The criteria I'm using for choosing are: Gives the correct impression of the result of the method call (i.e. that it's the original list with an extra element) Makes it as clear as possible that it doesn't mutate the existing list Sounds reasonable when chained together as in the second example above Please ask for more details if I'm not making myself clear enough... EDIT 1: Here's my reasoning for preferring Plus to Add. Consider these two lines of code: list.Add(foo); list.Plus(foo); In my view (and this is a personal thing) the latter is clearly buggy - it's like writing "x + 5;" as a statement on its own. The first line looks like it's okay, until you remember that it's immutable. In fact, the way that the plus operator on its own doesn't mutate its operands is another reason why Plus is my favourite. Without the slight ickiness of operator overloading, it still gives the same connotations, which include (for me) not mutating the operands (or method target in this case). EDIT 2: Reasons for not liking Add. Various answers are effectively: "Go with Add. That's what DateTime does, and String has Replace methods etc which don't make the immutability obvious." I agree - there's precedence here. However, I've seen plenty of people call DateTime.Add or String.Replace and expect mutation. There are loads of newsgroup questions (and probably SO ones if I dig around) which are answered by "You're ignoring the return value of String.Replace; strings are immutable, a new string gets returned." Now, I should reveal a subtlety to the question - the type might not actually be an immutable list, but a different immutable type. In particular, I'm working on a benchmarking framework where you add tests to a suite, and that creates a new suite. It might be obvious that: var list = new ImmutableList<string>(); list.Add("foo"); isn't going to accomplish anything, but it becomes a lot murkier when you change it to: var suite = new TestSuite<string, int>(); suite.Add(x => x.Length); That looks like it should be okay. Whereas this, to me, makes the mistake clearer: var suite = new TestSuite<string, int>(); suite.Plus(x => x.Length); That's just begging to be: var suite = new TestSuite<string, int>().Plus(x => x.Length); Ideally, I would like my users not to have to be told that the test suite is immutable. I want them to fall into the pit of success. This may not be possible, but I'd like to try. I apologise for over-simplifying the original question by talking only about an immutable list type. Not all collections are quite as self-descriptive as ImmutableList<T> :)

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• How can I read individual lines of a CSV file into a string array, to then be selectively displayed

  - by Ryan

  I need your help, guys! :| I've got myself a CSV file with the following contents: 1,The Compact,1.8GHz,1024MB,160GB,440 2,The Medium,2.4GHz,1024MB,180GB,500 3,The Workhorse,2.4GHz,2048MB,220GB,650 It's a list of computer systems, basically, that the user can purchase. I need to read this file, line-by-line, into an array. Let's call this array csvline(). The first line of the text file would stored in csvline(0). Line two would be stored in csvline(1). And so on. (I've started with zero because that's where VB starts its arrays). A drop-down list would then enable the user to select 1, 2 or 3 (or however many lines/systems are stored in the file). Upon selecting a number - say, 1 - csvline(0) would be displayed inside a textbox (textbox1, let's say). If 2 was selected, csvline(1) would be displayed, and so on. It's not the formatting I need help with, though; that's the easy part. I just need someone to help teach me how to read a CSV file line-by-line, putting each line into a string array - csvlines(count) - then increment count by one so that the next line is read into another slot. So far, I've been able to paste the numbers of each system into an combobox: Using csvfileparser As New Microsoft.VisualBasic.FileIO.TextFieldParser _ ("F:\folder\programname\programname\bin\Debug\systems.csv") Dim csvalue As String() csvfileparser.TextFieldType = Microsoft.VisualBasic.FileIO.FieldType.Delimited csvfileparser.Delimiters = New String() {","} While Not csvfileparser.EndOfData csvalue = csvfileparser.ReadFields() combobox1.Items.Add(String.Format("{1}{0}", _ Environment.NewLine, _ csvalue(0))) End While End Using But this only selects individual values. I need to figure out how selecting one of these numbers in the combobox can trigger textbox1 to be appended with just that line (I can handle the formatting, using the string.format stuff). If I try to do this using csvalue = csvtranslator.ReadLine , I get the following error message: "Error 1 Value of type 'String' cannot be converted to '1-dimensional array of String'." If I then put it as an array, ie: csvalue() = csvtranslator.ReadLine , I then get a different error message: "Error 1 Number of indices is less than the number of dimensions of the indexed array." What's the knack, guys? I've spent hours trying to figure this out. Please go easy on me - and keep any responses ultra-simple for my newbie brain - I'm very new to all this programming malarkey and just starting out! :)

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• How to optimize my PageRank calculation?

  - by asmaier

  In the book Programming Collective Intelligence I found the following function to compute the PageRank: def calculatepagerank(self,iterations=20): # clear out the current PageRank tables self.con.execute("drop table if exists pagerank") self.con.execute("create table pagerank(urlid primary key,score)") self.con.execute("create index prankidx on pagerank(urlid)") # initialize every url with a PageRank of 1.0 self.con.execute("insert into pagerank select rowid,1.0 from urllist") self.dbcommit() for i in range(iterations): print "Iteration %d" % i for (urlid,) in self.con.execute("select rowid from urllist"): pr=0.15 # Loop through all the pages that link to this one for (linker,) in self.con.execute("select distinct fromid from link where toid=%d" % urlid): # Get the PageRank of the linker linkingpr=self.con.execute("select score from pagerank where urlid=%d" % linker).fetchone()[0] # Get the total number of links from the linker linkingcount=self.con.execute("select count(*) from link where fromid=%d" % linker).fetchone()[0] pr+=0.85*(linkingpr/linkingcount) self.con.execute("update pagerank set score=%f where urlid=%d" % (pr,urlid)) self.dbcommit() However, this function is very slow, because of all the SQL queries in every iteration >>> import cProfile >>> cProfile.run("crawler.calculatepagerank()") 2262510 function calls in 136.006 CPU seconds Ordered by: standard name ncalls tottime percall cumtime percall filename:lineno(function) 1 0.000 0.000 136.006 136.006 <string>:1(<module>) 1 20.826 20.826 136.006 136.006 searchengine.py:179(calculatepagerank) 21 0.000 0.000 0.528 0.025 searchengine.py:27(dbcommit) 21 0.528 0.025 0.528 0.025 {method 'commit' of 'sqlite3.Connecti 1 0.000 0.000 0.000 0.000 {method 'disable' of '_lsprof.Profiler 1339864 112.602 0.000 112.602 0.000 {method 'execute' of 'sqlite3.Connec 922600 2.050 0.000 2.050 0.000 {method 'fetchone' of 'sqlite3.Cursor' 1 0.000 0.000 0.000 0.000 {range} So I optimized the function and came up with this: def calculatepagerank2(self,iterations=20): # clear out the current PageRank tables self.con.execute("drop table if exists pagerank") self.con.execute("create table pagerank(urlid primary key,score)") self.con.execute("create index prankidx on pagerank(urlid)") # initialize every url with a PageRank of 1.0 self.con.execute("insert into pagerank select rowid,1.0 from urllist") self.dbcommit() inlinks={} numoutlinks={} pagerank={} for (urlid,) in self.con.execute("select rowid from urllist"): inlinks[urlid]=[] numoutlinks[urlid]=0 # Initialize pagerank vector with 1.0 pagerank[urlid]=1.0 # Loop through all the pages that link to this one for (inlink,) in self.con.execute("select distinct fromid from link where toid=%d" % urlid): inlinks[urlid].append(inlink) # get number of outgoing links from a page numoutlinks[urlid]=self.con.execute("select count(*) from link where fromid=%d" % urlid).fetchone()[0] for i in range(iterations): print "Iteration %d" % i for urlid in pagerank: pr=0.15 for link in inlinks[urlid]: linkpr=pagerank[link] linkcount=numoutlinks[link] pr+=0.85*(linkpr/linkcount) pagerank[urlid]=pr for urlid in pagerank: self.con.execute("update pagerank set score=%f where urlid=%d" % (pagerank[urlid],urlid)) self.dbcommit() This function is 20 times faster (but uses a lot more memory for all the temporary dictionaries) because it avoids the unnecessary SQL queries in every iteration: >>> cProfile.run("crawler.calculatepagerank2()") 64802 function calls in 6.950 CPU seconds Ordered by: standard name ncalls tottime percall cumtime percall filename:lineno(function) 1 0.004 0.004 6.950 6.950 <string>:1(<module>) 1 1.004 1.004 6.946 6.946 searchengine.py:207(calculatepagerank2 2 0.000 0.000 0.104 0.052 searchengine.py:27(dbcommit) 23065 0.012 0.000 0.012 0.000 {meth 'append' of 'list' objects} 2 0.104 0.052 0.104 0.052 {meth 'commit' of 'sqlite3.Connection 1 0.000 0.000 0.000 0.000 {meth 'disable' of '_lsprof.Profiler' 31298 5.809 0.000 5.809 0.000 {meth 'execute' of 'sqlite3.Connectio 10431 0.018 0.000 0.018 0.000 {method 'fetchone' of 'sqlite3.Cursor' 1 0.000 0.000 0.000 0.000 {range} But is it possible to further reduce the number of SQL queries to speed up the function even more?

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• Save gcc compile status to a text file for Java

  - by JohnBore

  I'm making a C Assessment Program through Java, which has a bunch of programming questions for C, and it lets the user input an answer in the form of C code, and then press a "Compile" button, which is linked to a bat file that runs the user input code through gcc. I've got the input and compiling working, but I need to get the output from the compiler and get that to print textarea within the program. I can get a simple "Hello, world" compiling, but I'm having trouble getting programs that require a user input with scanf, for example, to be printed. else if(e.getSource().equals(compile)){ if(questionNumber<1){ JOptionPane.showMessageDialog(programFrame, "Please start the assessment", "Compile Error", JOptionPane.ERROR_MESSAGE); } else{ FileOutputStream fileWrite; try { fileWrite = new FileOutputStream("demo/demo.c"); new PrintStream(fileWrite).println(input.getText());//saves what the user has entered in to a C source file fileWrite.close(); @SuppressWarnings("unused") Process process = Runtime.getRuntime().exec("cmd /c compile.bat");//runs the batch file to compile the source file compileCode(); try{ fileStream = new FileInputStream("demo/output.txt"); inputStream = new DataInputStream(fileStream); bufferRead = new BufferedReader(new InputStreamReader(inputStream)); while((stringLine = bufferRead.readLine())!=null){ compiled.append(stringLine); compiled.append("\n"); } inputStream.close(); } catch(IOException exc){ System.err.println("Unable to read file"); System.exit(-1); } } catch (IOException exc) { JOptionPane.showMessageDialog(programFrame, "Demo file not found", "File Error", JOptionPane.ERROR_MESSAGE); } } This is the actionPerformed method for the "Compile" button, the compileCode() is the JFrame that displays the output and "compiled" is the textArea for the output. My batch file is: C: cd dev-cpp\bin gcc.exe H:\workspace\QuestionProgram\demo\demo.c -o demo > H:\workspace\QuestionProgram\demo\compilestatus.txt demo > H:\workspace\QuestionProgram\demo\output.txt I'm not sure how I can do it, so the frame is created for the output of the code if the code requires a user input as the command prompt doesn't open without adding "START" to .exec(), but then the frame appears before the program has finished running. Also, how would I get the output of the compiler if the compile fails because of an error? The way I've got it in my batch file at the moment doesn't put anything in a text file if it fails.

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• Creating a Blog ruby on Rails - Problem Deleting Comments

  - by bgadoci

  As I always type I am new to rails and programming in general so go easy. Thanks in advance. I have successfully followed the initial tutorial from Ryan Bates on how to build a weblog in 15 minutes. If you don't know this tutorial takes you through creating posts and allowing for comments on those post. It even introduces AJAX through the creating and displaying comments on the posts show.html.erb page. All works great. Here's the hiccup, when Ryan takes you though this tutorial he clears out the comments_controller and only shows the code for creating comments. I am trying to add back the ability to edit and destroy comments. Can't see to get it to work, keeps deleting the actual post not the comment (log shows that I keep sending DELETE request to PostsController). Here is my code: class CommentsController < ApplicationController def create @post = Post.find(params[:post_id]) @comment = @post.comments.create!(params[:comment]) respond_to do |format| format.html { redirect_to @post } format.js end end def destroy @comment = Comment.find(params[:id]) @comment.destroy respond_to do |format| format.html { redirect_to(posts_url) } format.xml { head :ok } end end end /views/posts/show.html.erb <%= render :partial => @post %> <p> <%= link_to 'Edit', edit_post_path (@post) %> | <%= link_to 'Destroy', @post, :method => :delete, :confirm => "Are you sure?" %> | <%= link_to 'See All Posts', posts_path %> </p> <h2>Comments</h2> <div id="comments"> <%= render :partial => @post.comments %> </div> <% remote_form_for [@post, Comment.new] do |f| %> <p> <%= f.label :body, "New Comment" %><br/> <%= f.text_area :body %> </p> <p> <%= f.submit "Add Comment" %></p> <% end %> /views/comments/_comment.html.erb <% div_for comment do %> <p> <strong>Posted <%= time_ago_in_words(comment.created_at) %> ago </strong><br/> <%= h(comment.body) %><br/> <%= link_to 'Destroy', @comments, :method => :delete, :confirm => "Are you sure?" %> </p> <% end %>

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• Gateway Page Between ASP and an ASP.NET Page

  - by ajdams

  I'll admit, I am pretty new with ASP .NET programming and I have been asked to take all our gateway pages (written in classic ASP) and make one universal gateway page to the few C# .NET applications we have (that I wrote). I tried searching here and the web and couldn't find much of anything describing a great way to do this and figured I was either not searching properly or was not properly naming what I am trying to do. I decided to to take one of the main gateway pages we had in classic ASP and use that as a base for my new gateway. Without boring you with a bunch of code I will summarize my gateway in steps and then can take advice/critique from there. EDIT: Basically what I am trying to do is go from a classic ASP page to a ASP .NET page and then back again. EDIT2: If my question is still unclear I am asking if what I have an the right start and if anyone has suggestions as to how this could be better. It can be as generic as need-be, not looking for a specific off-the-shelf code answer. My Gateway page: In the first part of the page I grab session variables and determine if the user is leaving or returning through the gateway: Code (in VB): uid = Request.QueryString("GUID") If uid = "" Then direction = "Leaving" End If ' Gather available user information. userid = Session("lnglrnregid") bankid = Session("strBankid") ' Return location. floor = Request.QueryString("Floor") ' The option chosen will determine if the user continues as SSL or not. ' If they are currently SSL, they should remain if chosen. option1 = Application(bankid & "Option1") If MID(option1, 6, 1) = "1" Then sslHttps = "s" End If Next I enter the uid into a database table (SQL-Server 2005) as a uniqueidentifier field called GUID. I omitted the stored procedure call. Lastly, I use the direction variable to determine if the user is leaving or returning and do redirects from there to the different areas of the site. Code (In VB again): If direction = "Leaving" Then Select Case floor Case "sscat", "ssassign" ' A SkillSoft course Response.Redirect("Some site here") Case "lrcat", "lrassign" ' A LawRoom course Response.Redirect("Some site here") Case Else ' Some other SCORM course like MindLeaders or a custom upload. Response.Redirect("Some site here") End Select Session.Abandon Else ' The only other direction is "Returning" ..... That's about it so far - so like I said, not an expert so any suggestions would be greatly appreciated!

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• move element li into ul with jquery

  - by ron

  Hi everybody i'm looking for a solution to move an element that i need to move into a .... im using jquery and i leave here the code i tried with different things but wasn't working it. this is the big menu <ul class="sf-menu"> <li><a href="">Student Centre</a> <ul> <li><a href="9">STUDENT CENTRAL WEBSITE</a></li> <li><a href="10">STUDENT CENTRAL EMAIL</a></li> <li><a href="11">CCM STUDENT SURVIAL TIPS</a></li> <li><a href="12">VET TUTTTION ASSURANSE</a></li> <li><a href="13">WHAT GOING ON AT CCM</a></li> <li><a href="14">IMPORTANT STUDENTS NOTICE</a></li> </ul> </li> <li><a href="">Research</a> <ul> <li><a href="_16">WHAT IS HOLISTIC KINESIOLOGY ?</a></li> <li><a href="_17">TRANF. CHILDREN W/ LEARNING DIFFICULTIES</a></li> <li><a href="_18">HEALING WITH HOLISTIC KINESIOLOGY</a></li> <li><a href="_19">UNDERSTANDING ASPERGER'S SYNDROME</a></li> <li><a href="_20">DAVID CORBY THE DIRECTOR OF CCM</a></li> <li><a href="_21">HELPING PEOPLE CREATE THEIR OWN MIRACLES</a></li> <li><a href="_22">MAGNESIUM AND COLLOIDAL MINERALS</a></li> <li><a href="_23">BRAIN ENERGETICS CHAKRAS AND NADIS</a></li> <li><a href="_24">KINESIOLOGY FAQ'S</a></li>' </ul> </li> <li><a href="25">Contact Us</a></li> <li><a href="26">A - Z</a></li> </ul> and i need to add this li to ul but i need to put in the second place after the first not nested <li id="faculty"> <a href="#">Faculty Courses </a> <ul> <li><a href="">INTENSE SHORT COURSES</a><ul> <li><a href="_59">CRYSTAL KINESIOLOGY ONE</a></li> <li><a href="_60">APPLIED PHYSIOLOGY</a></li> <li><a href="_61">VIBRATIONAL HEALING SYSTEMS 1</a></li> <li><a href="_62">VIBRATIONAL HEALING SYSTEMS 2</a></li> <li><a href="_63">VIBRATIONAL HEALING SYSTEMS 3</a></li> <li><a href="_64">VIBRATIONAL HEALING SYSTEMS 6</a></li> <li><a href="_65">NUTRITIONAL KINESIOLOGY</a></li> <li><a href="_66">QUANTUM HARMONICS</a></li><li><a href="_67">CHAKRA HOLOGRAM</a></li> <li><a href="_68">CLINICAL APPLICATIONS OF KINESIOLOGY</a></li> <li><a href="_69">COUNSELLING KINESIOLOGY</a></li> <li><a href="_70">HARMONISING CHI FLOW</a></li> </ul> </li> <li><a href="=53">FREE INTRUCTION COURSE DAYS</a> <ul> <li><a href="=53_56">HOLISTIC KINESIOLOGY</a></li> <li><a href="=53_57">TRANSPERSONAL COUNSELLING</a></li> <li><a href="=53_58">SHAMMANISM &amp; TRANSFORMATIONAL MASK</a></li> </ul> </li> <li><a href="=50">DIPLOMA MASK AND TRADITIONAL HEALING</a></li> <li><a href="=43">DIPLOMA TRANSPERSONAL ART THERAPY</a></li> <li><a href="=42">DIPLOMA HOLISTIC KINESIOLOGY</a></li> <li><a href="=47">ADVANCE DIPLOMA HOLISTIC KINESIOLOGY</a></li> <li><a href="=48">DIPLOMA DINAMIC AND FUNCTIONAL</a></li> <li><a href="=49">CERTIFICATE MASK AND TRADITIONAL HEALING</a></li> <li><a href="=51">DIPLOMA TRANSPERSONAL COUNSELLING</a></li> <li><a href="=52">STUDENT CLINICS</a></li> </ul> </li> please i need you help Thanks in advance

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• how to read input with multiple lines in java

  - by Gandalf StormCrow

  Hi all, Our professor is making us do some basic programming with java, he gaves a website and everything to register and submit our questions, for today I need to do this one example I feel like I'm on the right track but I just can't figure out the rest .. here is the actualy question : **Sample Input:** 10 12 10 14 100 200 **Sample Output:** 2 4 100 And here is what I've got so far : public class Practice { public static int calculateAnswer(String a, String b) { return (Integer.parseInt(b) - Integer.parseInt(a)); } public static void main(String[] args) { System.out.println(calculateAnswer(args[0], args[1])); } } Now I always get the answer 2 because I'm reading the single line, how can I take all lines into account? thank you For some strange reason everytime I want to execute I get this error: C:\sonic>java Practice.class 10 12 Exception in thread "main" java.lang.NoClassDefFoundError: Fact Caused by: java.lang.ClassNotFoundException: Fact.class at java.net.URLClassLoader$1.run(URLClassLoader.java:20 at java.security.AccessController.doPrivileged(Native M at java.net.URLClassLoader.findClass(URLClassLoader.jav at java.lang.ClassLoader.loadClass(ClassLoader.java:307 at sun.misc.Launcher$AppClassLoader.loadClass(Launcher. at java.lang.ClassLoader.loadClass(ClassLoader.java:248 Could not find the main class: Practice.class. Program will exit. Whosever version of answer I use I get this error, what do I do ? However if I run it in eclipse Run as Run Configuration - Program arguments 10 12 10 14 100 200 I get no output EDIT I have made some progress, at first I was getting the compilation error, then runtime error and now I get wrong answer , so can anybody help me what is wrong with this : import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.math.BigInteger; public class Practice { public static BigInteger calculateAnswer(String a, String b) { BigInteger ab = new BigInteger(a); BigInteger bc = new BigInteger(b); return bc.subtract(ab); } public static void main(String[] args) throws IOException { BufferedReader stdin = new BufferedReader(new InputStreamReader(System.in)); String line; while ((line = stdin.readLine()) != null && line.length()!= 0) { String[] input = line.split(" "); if (input.length == 2) { System.out.println(calculateAnswer(input[0], input[1])); } } } }

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• Time complexity of a sorting algorithm

  - by Passonate Learner

  The two programs below get n integers from file and calculates the sum of ath to bth integers q(number of question) times. I think the upper program has worse time complexity than the lower, but I'm having problems calculating the time complexity of these two algorithms. [input sample] 5 3 5 4 3 2 1 2 3 3 4 2 4 [output sample] 7 5 9 Program 1: #include <stdio.h> FILE *in=fopen("input.txt","r"); FILE *out=fopen("output.txt","w"); int n,q,a,b,sum; int data[1000]; int main() int i,j; fscanf(in,"%d%d",&n,&q); for(i=1;i<=n;i++) fscanf(in,"%d",&data[i]); for i=0;i<q;i++) { fscanf(in,"%d%d",&a,&b); sum=0; for(j=a;j<=b;j++) sum+=data[j]; fprintf(out,"%d\n",sum); } return 0; } Program 2: #include <stdio.h> FILE *in=fopen("input.txt","r"); FILE *out=fopen("output.txt","w"); int n,q,a,b; int data[1000]; int sum[1000]; int main() { int i,j; fscanf(in,"%d%d",&n,&q); for(i=1;i<=n;i++) fscanf(in,"%d",&data[i]); for(i=1;i<=n;i++) sum[i]=sum[i-1]+data[i]; for(i=0;i<q;i++) { fscanf(in,"%d%d",&a,&b); fprintf(out,"%d\n",sum[b]-sum[a-1]); } return 0; } The programs below gets n integers from 1 to m and sorts them. Again, I cannot calculate the time complexity. [input sample] 5 5 2 1 3 4 5 [output sample] 1 2 3 4 5 Program: #include <stdio.h> FILE *in=fopen("input.txt","r") FILE *out=fopen("output.txt","w") int n,m; int data[1000]; int count[1000]; int main() { int i,j; fscanf(in,"%d%d",&n,&m); for(i=0;i<n;i++) { fscanf(in,"%d",&data[i]); count[data[i]]++ } for(i=1;i<=m;i++) { for(j=0;j<count[i];j++) fprintf(out,"%d ",i); } return 0; } It's ironic(or not) that I cannot calculate the time complexity of my own algorithms, but I have passions to learn, so please programming gurus, help me!

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• Asynchronous sockets in C#

  - by IVlad

  I'm confused about the correct way of using asynchronous socket methods in C#. I will refer to these two articles to explain things and ask my questions: MSDN article on asynchronous client sockets and devarticles.com article on socket programming. My question is about the BeginReceive() method. The MSDN article uses these two functions to handle receiving data: private static void Receive(Socket client) { try { // Create the state object. StateObject state = new StateObject(); state.workSocket = client; // Begin receiving the data from the remote device. client.BeginReceive( state.buffer, 0, StateObject.BufferSize, 0, new AsyncCallback(ReceiveCallback), state); } catch (Exception e) { Console.WriteLine(e.ToString()); } } private static void ReceiveCallback( IAsyncResult ar ) { try { // Retrieve the state object and the client socket // from the asynchronous state object. StateObject state = (StateObject) ar.AsyncState; Socket client = state.workSocket; // Read data from the remote device. int bytesRead = client.EndReceive(ar); if (bytesRead > 0) { // There might be more data, so store the data received so far. state.sb.Append(Encoding.ASCII.GetString(state.buffer,0,bytesRead)); // Get the rest of the data. client.BeginReceive(state.buffer,0,StateObject.BufferSize,0, new AsyncCallback(ReceiveCallback), state); } else { // All the data has arrived; put it in response. if (state.sb.Length > 1) { response = state.sb.ToString(); } // Signal that all bytes have been received. receiveDone.Set(); } } catch (Exception e) { Console.WriteLine(e.ToString()); } } While the devarticles.com tutorial passes null for the last parameter of the BeginReceive method, and goes on to explain that the last parameter is useful when we're dealing with multiple sockets. Now my questions are: What is the point of passing a state to the BeginReceive method if we're only working with a single socket? Is it to avoid using a class field? It seems like there's little point in doing it, but maybe I'm missing something. How can the state parameter help when dealing with multiple sockets? If I'm calling client.BeginReceive(...), won't all the data be read from the client socket? The devarticles.com tutorial makes it sound like in this call: m_asynResult = m_socClient.BeginReceive (theSocPkt.dataBuffer,0,theSocPkt.dataBuffer.Length, SocketFlags.None,pfnCallBack,theSocPkt); Data will be read from the theSocPkt.thisSocket socket, instead of from the m_socClient socket. In their example the two are one and the same, but what happens if that is not the case? I just don't really see where that last argument is useful or at least how it helps with multiple sockets. If I have multiple sockets, I still need to call BeginReceive on each of them, right?

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• Why is django giving me an attribute error when I call _set.all() for its children models?

  - by user1876508

  I have two models defined from django.db import models class Blog(models.Model): title = models.CharField(max_length=144) @property def posts(self): self.Post_set.all() class Post(models.Model): title = models.CharField(max_length=144) text = models.TextField() blog = models.ForeignKey('Blog') but the problem is, when I run shell, and enter >>> blog = Blog(title="My blog") >>> post = Post(title="My first post", text="Here is the main text for my blog post", blog=blog) >>> blog.posts I get the error Traceback (most recent call last): File "<console>", line 1, in <module> File "/home/lucas/Programming/Python/Django/djangorestfun/blog/models.py", line 9, in posts self.Post_set.all() AttributeError: 'Blog' object has no attribute 'Post_set' >>> Now I am having the following problem >>> from blog.models import * >>> blog = Blog(title="gewrhter") >>> blog.save() >>> blog.__dict__ {'_state': <django.db.models.base.ModelState object at 0x259be10>, 'id': 1, 'title': 'gewrhter'} >>> blog._state.__dict__ {'adding': False, 'db': 'default'} >>> post = Post(title="sdhxcvb", text="hdbfdgb", blog=blog) >>> post.save() >>> post.__dict__ {'blog_id': 1, 'title': 'sdhxcvb', 'text': 'hdbfdgb', '_blog_cache': <Blog: Blog object>, '_state': <django.db.models.base.ModelState object at 0x259bed0>, 'id': 1} >>> blog.posts >>> print blog.posts None Second update So I followed your guide, but I am still getting nothing. In addition, blog.posts gives me an error. >>> from blog.models import * >>> blog = Blog(title="asdf") >>> blog.save() >>> post = Post(title="asdf", text="sdxcvb", blog=blog) >>> post.save() >>> blog.posts Traceback (most recent call last): File "<console>", line 1, in <module> AttributeError: 'Blog' object has no attribute 'posts' >>> print blog.all_posts None

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• Scheme Formatting Help

  - by Logan

  I've been working on a project for school that takes functions from a class file and turns them into object/classes. The assignment is all about object oriented programming in scheme. My problem however is that my code doesn't format right. The output it gives me whenever I give it a file to pass in wraps the methods of the class in a list, making it so that the class never really gets declared. I can't for the life of me figure out how to get the parenthesis wrapping the method list to remove. I would really appreciate any help. Below is the code and the class file. ;;;; PART1 --- A super-easy set of classes. Just models points and lines. Tests all of the ;; basics of class behavior without touching on anything particularly complex. (class pointInstance (parent:) (constructor_args:) (ivars: (myx 1) (myy 2)) (methods: (getx () myx) (gety () myy) (setx (x) (set! myx x)) (show () (begin (display "[") (display myx) (display ",") (display myy) (display "]"))) )) (require (lib "trace.ss")) ;; Continue reading until you hit the end of the file, all the while ;; building a list with the contents (define load-file (lambda (port) (let ((rec (read port))) (if (eof-object? rec) '() (cons rec (load-file port)))))) ;; Open a port based on a file name using open-input-file (define (load fname) (let ((fport (open-input-file fname))) (load-file fport))) ;(define lis (load "C:\\Users\\Logan\\Desktop\\simpletest.txt")) ;(define lis (load "C:\\Users\\Logan\\Desktop\\complextest.txt")) (define lis (load "C:\\Users\\Logan\\Desktop\\pointinstance.txt")) ;(display (cdaddr (cdddar lis))) (define makeMethodList (lambda (listToMake retList) ;(display listToMake) (cond [(null? listToMake) retList ;(display "The list passed in to parse was null") ] [else (makeMethodList (cdr listToMake) (append retList (list (getMethodLine listToMake)))) ] ) )) ;(trace makeMethodList) ;this works provided you just pass in the function line (define getMethodLine (lambda (functionList) `((eq? (car msg) ,(caar functionList)) ,(caddar functionList)))) (define load-classes (lambda paramList (cond [(null? paramList) (display "Your parameters are null, man.")] [(null? (car paramList))(display "Done creating class definitions.")] [(not (null? (car paramList))) (begin (let* ((className (cadaar paramList)) (classInstanceVars (cdaddr (cddaar paramList))) (classMethodList (cdr (cadddr (cddaar paramList)))) (desiredMethodList (makeMethodList classMethodList '())) ) ;(display "Classname: ") ;(display className) ;(newline)(newline) ;(display "Class Instance Vars: ") ;(display classInstanceVars) ;(newline)(newline) ;(display "Class Method List: ") ;(display classMethodList) ;(newline) ;(display "Desired Method List: ") ;(display desiredMethodList)) ;(newline)(newline) ;---------------------------------------------------- ;do not delete the below code!` `(define ,className (let ,classInstanceVars (lambda msg ;return the function list here (cond ,(makeMethodList classMethodList '()))) )) ;--------------------------------------------------- ))] ) )) (load-classes lis) ;(load-classes lis) ;(load-classes-helper lis) ;(load-classes "simpletest.txt") ;(load-classes "complextest.txt") ;method list ;(display (cdr (cadddr (cddaar <class>))))

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• What strategy do you use for package naming in Java projects and why?

  - by Tim Visher

  I thought about this awhile ago and it recently resurfaced as my shop is doing its first real Java web app. As an intro, I see two main package naming strategies. (To be clear, I'm not referring to the whole 'domain.company.project' part of this, I'm talking about the package convention beneath that.) Anyway, the package naming conventions that I see are as follows: Functional: Naming your packages according to their function architecturally rather than their identity according to the business domain. Another term for this might be naming according to 'layer'. So, you'd have a *.ui package and a *.domain package and a *.orm package. Your packages are horizontal slices rather than vertical. This is much more common than logical naming. In fact, I don't believe I've ever seen or heard of a project that does this. This of course makes me leery (sort of like thinking that you've come up with a solution to an NP problem) as I'm not terribly smart and I assume everyone must have great reasons for doing it the way they do. On the other hand, I'm not opposed to people just missing the elephant in the room and I've never heard a an actual argument for doing package naming this way. It just seems to be the de facto standard. Logical: Naming your packages according to their business domain identity and putting every class that has to do with that vertical slice of functionality into that package. I have never seen or heard of this, as I mentioned before, but it makes a ton of sense to me. I tend to approach systems vertically rather than horizontally. I want to go in and develop the Order Processing system, not the data access layer. Obviously, there's a good chance that I'll touch the data access layer in the development of that system, but the point is that I don't think of it that way. What this means, of course, is that when I receive a change order or want to implement some new feature, it'd be nice to not have to go fishing around in a bunch of packages in order to find all the related classes. Instead, I just look in the X package because what I'm doing has to do with X. From a development standpoint, I see it as a major win to have your packages document your business domain rather than your architecture. I feel like the domain is almost always the part of the system that's harder to grok where as the system's architecture, especially at this point, is almost becoming mundane in its implementation. The fact that I can come to a system with this type of naming convention and instantly from the naming of the packages know that it deals with orders, customers, enterprises, products, etc. seems pretty darn handy. It seems like this would allow you to take much better advantage of Java's access modifiers. This allows you to much more cleanly define interfaces into subsystems rather than into layers of the system. So if you have an orders subsystem that you want to be transparently persistent, you could in theory just never let anything else know that it's persistent by not having to create public interfaces to its persistence classes in the dao layer and instead packaging the dao class in with only the classes it deals with. Obviously, if you wanted to expose this functionality, you could provide an interface for it or make it public. It just seems like you lose a lot of this by having a vertical slice of your system's features split across multiple packages. I suppose one disadvantage that I can see is that it does make ripping out layers a little bit more difficult. Instead of just deleting or renaming a package and then dropping a new one in place with an alternate technology, you have to go in and change all of the classes in all of the packages. However, I don't see this is a big deal. It may be from a lack of experience, but I have to imagine that the amount of times you swap out technologies pales in comparison to the amount of times you go in and edit vertical feature slices within your system. So I guess the question then would go out to you, how do you name your packages and why? Please understand that I don't necessarily think that I've stumbled onto the golden goose or something here. I'm pretty new to all this with mostly academic experience. However, I can't spot the holes in my reasoning so I'm hoping you all can so that I can move on. Thanks in advance!

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• HP to Cisco spanning tree root flapping

  - by Tim Brigham

  Per a recent question I recently configured both my HP (2x 2900) and Cisco (1x 3750) hardware to use MSTP for interoperability. I thought this was functional until I applied the change to the third device (HP switch 1 below) at which time the spanning tree root started flapping causing performance issues (5% packet loss) between my two HP switches. I'm not sure why. HP Switch 1 A4 connected to Cisco 1/0/1. HP Switch 2 B2 connected to Cisco 2/0/1. HP Switch 1 A2 connected to HP Switch 2 A1. I'd prefer the Cisco stack to act as the root. EDIT: There is one specific line - 'spanning-tree 1 path-cost 500000' in the HP switch 2 that I didn't add and was preexisting. I'm not sure if it could have the kind of impact that I'm describing. I'm more a security and monitoring guy then networking. EDIT 2: I'm starting to believe the problem lies in the fact that the value for my MST 0 instance on the Cisco is still at the default 32768. I worked up a diagram: This is based on every show command I could find for STP. I'll make this change after hours and see if it helps. Cisco 3750 Config: version 12.2 spanning-tree mode mst spanning-tree extend system-id spanning-tree mst configuration name mstp revision 1 instance 1 vlan 1, 40, 70, 100, 250 spanning-tree mst 1 priority 0 vlan internal allocation policy ascending interface TenGigabitEthernet1/1/1 switchport trunk encapsulation dot1q switchport mode trunk ! interface TenGigabitEthernet2/1/1 switchport trunk encapsulation dot1q switchport mode trunk ! interface Vlan1 no ip address ! interface Vlan100 ip address 192.168.100.253 255.255.255.0 ! Cisco 3750 show spanning tree: show spanning-tree MST0 Spanning tree enabled protocol mstp Root ID Priority 32768 Address 0004.ea84.5f80 Cost 200000 Port 53 (TenGigabitEthernet1/1/1) Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 32768 (priority 32768 sys-id-ext 0) Address a44c.11a6.7c80 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Interface Role Sts Cost Prio.Nbr Type ------------------- ---- --- --------- -------- -------------------------------- Te1/1/1 Root FWD 2000 128.53 P2p MST1 Spanning tree enabled protocol mstp Root ID Priority 1 Address a44c.11a6.7c80 This bridge is the root Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 1 (priority 0 sys-id-ext 1) Address a44c.11a6.7c80 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Interface Role Sts Cost Prio.Nbr Type ------------------- ---- --- --------- -------- -------------------------------- Te1/1/1 Desg FWD 2000 128.53 P2p Cisco 3750 show logging: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state to down %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan100, changed state to down %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state to up %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan100, changed state to up %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state to down %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state to up HP Switch 1: ; J9049A Configuration Editor; Created on release #T.13.71 vlan 1 name "DEFAULT_VLAN" untagged 1-8,10,13-16,18-23,A1-A4 ip address 100.100.100.17 255.255.255.0 no untagged 9,11-12,17,24 exit vlan 100 name "192.168.100" untagged 9,11-12,17,24 tagged 1-8,10,13-16,18-23,A1-A4 no ip address exit vlan 21 name "Users_2" tagged 1,A1-A4 no ip address exit vlan 40 name "Cafe" tagged 1,4,7,A1-A4 no ip address exit vlan 250 name "Firewall" tagged 1,4,7,A1-A4 no ip address exit vlan 70 name "DMZ" tagged 1,4,7-8,13,A1-A4 no ip address exit spanning-tree spanning-tree config-name "mstp" spanning-tree config-revision 1 spanning-tree instance 1 vlan 1 40 70 100 250 password manager password operator HP Switch 1 show spanning tree: show spanning-tree Multiple Spanning Tree (MST) Information STP Enabled : Yes Force Version : MSTP-operation IST Mapped VLANs : 2-39,41-69,71-99,101-249,251-4094 Switch MAC Address : 0021f7-126580 Switch Priority : 32768 Max Age : 20 Max Hops : 20 Forward Delay : 15 Topology Change Count : 363,490 Time Since Last Change : 14 hours CST Root MAC Address : 0004ea-845f80 CST Root Priority : 32768 CST Root Path Cost : 200000 CST Root Port : 1 IST Regional Root MAC Address : 0021f7-126580 IST Regional Root Priority : 32768 IST Regional Root Path Cost : 0 IST Remaining Hops : 20 Root Guard Ports : TCN Guard Ports : BPDU Protected Ports : BPDU Filtered Ports : PVST Protected Ports : PVST Filtered Ports : | Prio | Designated Hello Port Type | Cost rity State | Bridge Time PtP Edge ----- --------- + --------- ---- ---------- + ------------- ---- --- ---- A1 | Auto 128 Disabled | A2 10GbE-CX4 | 2000 128 Forwarding | 0021f7-126580 2 Yes No A3 10GbE-CX4 | Auto 128 Disabled | A4 10GbE-SR | Auto 128 Disabled | HP Switch 1 Logging: I removed the date / time fields since they are inaccurate (no NTP configured on these switches) 00839 stp: MSTI 1 Root changed from 0:a44c11-a67c80 to 32768:0021f7-126580 00839 stp: MSTI 1 Root changed from 32768:0021f7-126580 to 0:a44c11-a67c80 00842 stp: MSTI 1 starved for an MSTI Msg Rx on port A4 from 0:a44c11-a67c80 00839 stp: MSTI 1 Root changed from 0:a44c11-a67c80 to 32768:0021f7-126580 00839 stp: MSTI 1 Root changed from 32768:0021f7-126580 to 0:a44c11-a67c80 00839 stp: MSTI 1 Root changed from 0:a44c11-a67c80 to ... HP Switch 2 Configuration: ; J9146A Configuration Editor; Created on release #W.14.49 vlan 1 name "DEFAULT_VLAN" untagged 1,3-17,21-24,A1-A2,B2 ip address 100.100.100.36 255.255.255.0 no untagged 2,18-20,B1 exit vlan 100 name "192.168.100" untagged 2,18-20 tagged 1,3-17,21-24,A1-A2,B1-B2 no ip address exit vlan 21 name "Users_2" tagged 1,A1-A2,B2 no ip address exit vlan 40 name "Cafe" tagged 1,13-14,16,A1-A2,B2 no ip address exit vlan 250 name "Firewall" tagged 1,13-14,16,A1-A2,B2 no ip address exit vlan 70 name "DMZ" tagged 1,13-14,16,A1-A2,B2 no ip address exit logging 192.168.100.18 spanning-tree spanning-tree 1 path-cost 500000 spanning-tree config-name "mstp" spanning-tree config-revision 1 spanning-tree instance 1 vlan 1 40 70 100 250 HP Switch 2 Spanning Tree: show spanning-tree Multiple Spanning Tree (MST) Information STP Enabled : Yes Force Version : MSTP-operation IST Mapped VLANs : 2-39,41-69,71-99,101-249,251-4094 Switch MAC Address : 0024a8-cd6000 Switch Priority : 32768 Max Age : 20 Max Hops : 20 Forward Delay : 15 Topology Change Count : 21,793 Time Since Last Change : 14 hours CST Root MAC Address : 0004ea-845f80 CST Root Priority : 32768 CST Root Path Cost : 200000 CST Root Port : A1 IST Regional Root MAC Address : 0021f7-126580 IST Regional Root Priority : 32768 IST Regional Root Path Cost : 2000 IST Remaining Hops : 19 Root Guard Ports : TCN Guard Ports : BPDU Protected Ports : BPDU Filtered Ports : PVST Protected Ports : PVST Filtered Ports : | Prio | Designated Hello Port Type | Cost rity State | Bridge Time PtP Edge ----- --------- + --------- ---- ---------- + ------------- ---- --- ---- A1 10GbE-CX4 | 2000 128 Forwarding | 0021f7-126580 2 Yes No A2 10GbE-CX4 | Auto 128 Disabled | B1 SFP+SR | 2000 128 Forwarding | 0024a8-cd6000 2 Yes No B2 | Auto 128 Disabled | HP Switch 2 Logging: I removed the date / time fields since they are inaccurate (no NTP configured on these switches) 00839 stp: CST Root changed from 32768:0021f7-126580 to 32768:0004ea-845f80 00839 stp: IST Root changed from 32768:0021f7-126580 to 32768:0024a8-cd6000 00839 stp: CST Root changed from 32768:0004ea-845f80 to 32768:0024a8-cd6000 00839 stp: CST Root changed from 32768:0024a8-cd6000 to 32768:0004ea-845f80 00839 stp: CST Root changed from 32768:0004ea-845f80 to 32768:0024a8-cd6000 00435 ports: port B1 is Blocked by STP 00839 stp: CST Root changed from 32768:0024a8-cd6000 to 32768:0021f7-126580 00839 stp: IST Root changed from 32768:0024a8-cd6000 to 32768:0021f7-126580 00839 stp: CST Root changed from 32768:0021f7-126580 to 32768:0004ea-845f80

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• Downloading Python 2.5.4 (from official website) in order to install it

  - by brilliant

  I was quite hesitant about whether I should post this question here on "StackOverflow" or on "SuperUser", but finally decided to post it here as Python is more a programming language rather than a piece of software. I've been recently using Python 2.5.4 that is installed on my computer, but at the moment I am not at home (and won't be for about two weeks from now), so I need to install the same version of Python on another computer. This computer has Windows XP installed – just like the one that I have at home. The reason why I need Python 2.5.4 is because I am using “Google App Engine”, and I was told that it only supports Python 2.5 However, when I went to the official Python page for the download, I discovered that certain things have changed, and I don’t quite remember where exactly from that site I had downloaded Python 2.5.4 on my computer at home. I found this page: http://www.python.org/download/releases/2.5.4/ Here is how it looks: (If you can’t see it here, please check it out at this address: http://brad.cwahi.net/some_pictures/python_page.jpg ) A few things here are not clear to me. It says: “For x86 processors: python-2.5.4.msi For Win64-Itanium users: python-2.5.4.ia64.msi For Win64-AMD64 users: python-2.5.4.amd64.msi” First of all, I don’t know what processor I am using – whether mine is “x86” or not; and also, I don’t know whether I am an “Win64-Itanium” or an “Win64-AMD64” user. Are Itanium and AMD64 also processors? Later it says: “Windows XP and later already have MSI; many older machines will already have MSI installed.” I guess, it is my case, but then I am totally puzzled as to which link I should click as it seems now that I don’t need those three previous links (as MSI is already installed on Windows XP), but there is no fourth link provided for those who use “Windows XP” or older machines. Of course, there are these words after that: “Windows users may also be interested in Mark Hammond's win32all package, available from Sourceforge.” but it seems to me that it is something additional rather than the main file. So, my question is simple: Where in the official Python website I can download Python 2.5.4, precisely, which link I should click?

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• How to read the 3D chart data with directX?

  - by MemoryLeak

  I am reading a open source project, and I found there is a function which read 3D data(let's say a character) from obj file, and draw it . the source code: List<Vertex3f> verts=new List<Vertex3f>(); List<Vertex3f> norms=new List<Vertex3f>(); Groups=new List<ToothGroup>(); //ArrayList ALf=new ArrayList();//faces always part of a group List<Face> faces=new List<Face>(); MemoryStream stream=new MemoryStream(buffer); using(StreamReader sr = new StreamReader(stream)){ String line; Vertex3f vertex; string[] items; string[] subitems; Face face; ToothGroup group=null; while((line = sr.ReadLine()) != null) { if(line.StartsWith("#")//comment || line.StartsWith("mtllib")//material library. We build our own. || line.StartsWith("usemtl")//use material || line.StartsWith("o")) {//object. There's only one object continue; } if(line.StartsWith("v ")) {//vertex items=line.Split(new char[] { ' ' }); vertex=new Vertex3f();//float[3]; if(flipHorizontally) { vertex.X=-Convert.ToSingle(items[1],CultureInfo.InvariantCulture); } else { vertex.X=Convert.ToSingle(items[1],CultureInfo.InvariantCulture); } vertex.Y=Convert.ToSingle(items[2],CultureInfo.InvariantCulture); vertex.Z=Convert.ToSingle(items[3],CultureInfo.InvariantCulture); verts.Add(vertex); continue; } And why it need to read the data manually in directX? As far as I know, in XDA programming, we just need to call a function a load the resource. Is this because it is in DirectX, there is no function to read resource? If yes, then how to prepare the 3D resource ? in XDA we just need to use other software draw the 3D picture and then export. but what should I do in DirectX?

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• Opera Mobile, offline web app development, and memory

  - by Jake Krohn

  I'm developing a data collection app for use on a HP iPAQ 211. I'm doing it as an offline web app (go with what you know) using Opera Mobile 9.7 and Google Gears. Being it is an offline app, it is very dependent on Javascript for much of its behavior. I'm using the LocalServer, Database, and Geolocation components of Gears, as well as the JQuery core and a couple of plugins for form validation and other usability tweaks (no jQuery UI). I've tried to be conservative with my programming style and free up or close resources whenever possible, but Opera just slowly dies after about 10-20 minutes of use. The Javascript engine stops responding, pages only half-load, and eventually stop loading completely. I'm guessing it's a resource issue. Quitting and relaunching the browser solves the problem, but only temporarily. The iPAQ ships with 128 MB of RAM, about 85-87 MB of which is available immediately after a reset. With only Opera running, there still remains about 50 MB that is left unused. My questions are thus: Is it possible to get Opera to address this unused RAM? Are there configuration settings in Opera or in the Windows Registry itself that will help improve performance? I know where to tweak, but the descriptions of the opera:config variables that I've found are less than helpful. Is is laughable to ask about memory management and jQuery in the same sentence? If not, does anyone have any suggestions? Finally, are my plans too ambitious, given the platform I have to work with? I know that Gears and Windows Mobile 6 are on their way out, but they (theoretically) suffice for what I need to do. I could ditch them in favor of an iPhone/iPod Touch, Mobile Safari, and HTML5 but I'd like to try to make this work first. I didn't think that Opera was a dog when it comes to JS performance, but perhaps it's worse than I thought. That this motley collection of technologies works at all is a minor miracle, but it needs to be faster and more stable. I appreciate any suggestions.

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• Daylight saving time and Timezone best practices

  - by Oded

  I am hoping to make this question and the answers to it the definitive guide to dealing with daylight saving time, in particular for dealing with the actual change overs. If you have anything to add, please do Many systems are dependent on keeping accurate time, the problem is with changes to time due to daylight savings - moving the clock forward or backwards. For instance, one has business rules in an order taking system that depend on the time of the order - if the clock changes, the rules might not be as clear. How should the time of the order be persisted? There is of course an endless number of scenarios - this one is simply an illustrative one. How have you dealt with the daylight saving issue? What assumptions are part of your solution? (looking for context here) As important, if not more so: What did you try that did not work? Why did it not work? I would be interested in programming, OS, data persistence and other pertinent aspects of the issue. General answers are great, but I would also like to see details especially if they are only available on one platform. Summary of answers and other data: (please add yours) Do: Always persist time according to a unified standard that is not affected by daylight savings. GMT and UTC have been mentioned by different people. Include the local time offset (including DST offset) in stored timestamps. Remember that DST offsets are not always an integer number of hours (e.g. Indian Standard Time is UTC+05:30). If using Java, use JodaTime. - http://joda-time.sourceforge.net/ Create a table TZOffsets with three columns: RegionClassId, StartDateTime, and OffsetMinutes (int, in minutes). See answer Check if your DBMS needs to be shutdown during transition. Business rules should always work on civil time. Internally, keep timestamps in something like civil-time-seconds-from-epoch. See answer Only convert to local times at the last possible moment. Don't: Do not use javascript date and time calculations in web apps unless you ABSOLUTELY have to. Testing: When testing make sure you test countries in the Western and Eastern hemispheres, with both DST in progress and not and a country that does not use DST (6 in total). Reference: Olson database, aka Tz_database - ftp://elsie.nci.nih.gov/pub Sources for Time Zone and DST - http://www.twinsun.com/tz/tz-link.htm ISO format (ISO 8601) - http://en.wikipedia.org/wiki/ISO_8601 Mapping between Olson database and Windows TimeZone Ids, from the Unicode Consortium - http://unicode.org/repos/cldr-tmp/trunk/diff/supplemental/windows_tzid.html TimeZone page on WikiPedia - http://en.wikipedia.org/wiki/Tz_database StackOverflow questions tagged dst - http://stackoverflow.com/questions/tagged/dst StackOverflow questions tagged timezone - http://stackoverflow.com/questions/tagged/timezone Other: Lobby your representative to end the abomination that is DST. We can always hope...

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• From a 3D modeler to an iPhone app - what are best practices?

  - by bonkey

  I am quite new in 3D programming on iPhone and I would like to ask for hints about organizing a work between designers and programmers on that platform. Most of all: what kind of tools, libraries or plugins cooperate the best on both sides. Although I consider the question as looking for general best-practices advice I would like to find a solution for my current situation which I describe further, too. I've already done some research and found following libraries: SIO2 Khronos OpenGL ES 1.x SDK for PowerVR MBX Unity3D Oolong Game Engine I've checked modellers or plugins to them giving output formats readable by those tools: obj2opengl Wavefront OBJ to plain header file converter Blender with SIO2 exporter iphonewavefrontloader Cheetah3D PVRGeoPOD for 3DS / Maya Unfortunately I still have no clear vision how to combine any of that tools to get a desinger's work in an application. I look for a way of getting it in the most possible complete way: models, lights, scenes, textures, maybe some simple animations (but rather no game-like physics), but I still got nothing. And here comes my situation: I would like to find right way to present few (but quite complicated) models from a single scene. The designers mostly use 3DS Max 9, sometimes 10 (which partly prevents using PVRGeoPOD) and are rather reluctant to switch to something else but if there's no other choice I suppose it would be possible. The basic rule I've already found in some places "use Wavefront OBJ" not always works. I haven't got any acceptable results with production files, actually. The only things worked fine were some mere examples. Some of my models did imported incomplete, sometimes exporters hung or generated enormous files not really useful on an iPhone, sometimes enabling textures (with GL_TEXTURE_2D) just crashed an app. I know it might be a problem with too complicated models or my mistakes coming from inexeperience but I am not able to find any guidelines for that process to have streamlined cooperation with designers. I am even willing to write some things from scratch in pure OpenGL-ES if it's necessary, but I would like to avoid what might be avoided and get the most from the model files. The best would be the effect I saw on some SIO2 tutorials: export, build & go. But at that moment I've got only "import, wrong", "import, where are textures?", "import, that almost looks fine, export, hang" and so on... Is it really so much frustrating or I am just missed something obvious? Can anybody share his/her experience in that field and tell what kind of software uses for "making things happen"?

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• Using in app purchase to unlock features vs. using free & paid app versions for iPhone

  - by yabada

  I have an app that I was going to release as a free (lite) version with some of the total functionality and a paid full version with advanced functionality. Now, with in app purchase for free apps I am thinking of going that route with the ability to unlock features as needed. I'm not talking about a trial version that expires.I want people to be able to try out the app and get an idea of the interface and functionality before deciding to purchase the full functionality of each major section of the app, basically. Here's an analogy of what my app would be like. Let's say you have a cooking app that teaches you to cook in different styles. There could be major section for French, Italian, and Chinese. Each section could have some rudiments unlocked in the free app so users can see the UI and basics of the functionality. Then, the user could decide to purchase each major section (or not) individually with in app purchase or buy the full versioned app (with the free/paid model). One concern I have with offering a free app with in app purchase would be with feedback. I would be very clear in my description in the app store that there is in app purchase for full features but I'm worried that less serious users could/would leave negative feedback. I suppose that's always a risk but curious about any experience with this. It also seems that it could be a whole lot more complicated keeping track of what portions of the app are locked and unlocked with in app purchase. I know I'd have to have all the code for the full functionality and "lock" the portions that haven't been purchased. How do people usually lock portions of their code? I'm not talking about the process of purchasing (I've read the In App Purchase Programming Guide) but after the purchase has been made. Would I just keep track of what the user has purchased and put conditionals on the sections that are initially locked? Or is there another way to do this as well? My instinct is for the in app purchase (particularly since users could purchase the major sections that they want individually).

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• iGoogle Stack Overflow Gadget [closed]

  - by Charango

  Since SO's question database is becoming an excellent first point of call for finding answers to coding problems, some people (like me) might like to be able to fire up searches from their iGoogle home page, among the other searches you might launch from there. I've created a very simple gadget to do this, and put the source below. My hope is that this might provide a foundation on which community members with better ideas for performing this function, or ideas for enhancing it, can update it. Perhaps we could make it configurable to search via a site scope search from Google and / or a question search, for instance. I've hosted and registered this first version but if anyone makes changes and can host a new version / new pics elsewhere, please feel free. <?xml version="1.0" encoding="UTF-8"?> <Module> <ModulePrefs title="Stack Overflow Search" author="Community Wiki" author_email="[email protected]" author_affiliation="Stack Overflow" author_location="The Internet" author_aboutme="All sorts" author_link="http://stackoverflow.com" author_quote="Hofstadter's Law: It always takes longer than you expect, even when you take into account Hofstadter's Law." description="Stack Overflow is rapidly becoming one of the best resources for finding answers to your programming questions. This gadget adds a question search box to your iGoogle homepage" screenshot="http://arkios-solutions.com/misc/sogadget/SOGadget.png" thumbnail="http://arkios-solutions.com/misc/sogadget/SOGadget_Thumbnail.png" singleton="true" title_url="http://stackoverflow.com" /> <Content type="html"><![CDATA[ <img src="http://i.stackoverflow.com/Content/Img/stackoverflow-logo-250.png" alt="Stackoverflow Logo"/> <div style="font-family:arial;font-size:0.8em;"> This gadget allows you to search the Stack Overflow question database. </div> <form name='SOQueryForm' action="http://stackoverflow.com/search" method="get" target="new"> <p>Your question: <input type='text' size='34' name='q' /></p> <p><input type='submit' value='Go' /></p> </form> ]]> </Content> </Module> The source / installable gadget xml are also hosted here.

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• Is Ogre's use of Exceptions a good way of using them?

  - by identitycrisisuk

  I've managed to get through my C++ game programming career so far virtually never touching exceptions but recently I've been working on a project with the Ogre engine and I'm trying to learn properly. I've found a lot of good questions and answers here on the general usage of C++ exceptions but I'd like to get some outside opinions from here on whether Ogre's usage is good and how best to work with them. To start with, quoting from Ogre's documentation of it's own Exception class: OGRE never uses return values to indicate errors. Instead, if an error occurs, an exception is thrown, and this is the object that encapsulates the detail of the problem. The application using OGRE should always ensure that the exceptions are caught, so all OGRE engine functions should occur within a try{} catch(Ogre::Exception& e) {} block. Really? Every single Ogre function could throw an exception and be wrapped in a try/catch block? At present this is handled in our usage of it by a try/catch in main that will show a message box with the exception description before exiting. This can be a bit awkward for debugging though as you don't get a stack trace, just the function that threw the error - more important is the function from our code that called the Ogre function. If it was an assert in Ogre code then it would go straight to the code in the debugger and I'd be able to find out what's going on much easier - I don't know if I'm missing something that would allow me to debug exceptions already? I'm starting to add a few more try/catch blocks in our code now, generally thinking about whether it matters if the Ogre function throws an exception. If it's something that will stop everything working then let the main try/catch handle it and exit the program. If it's not of great importance then catch it just after the function call and let the program continue. One recent example of this was building up a vector of the vertex/fragment program parameters for materials applied to an entity - if a material didn't have any parameters then it would throw an exception, which I caught and then ignored as it didn't need to add to my list of parameters. Does this seem like a reasonable way of dealing with things? Any specific advice for working with Ogre is much appreciated.

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• How to create a Uri instance parsed with GenericUriParserOptions.DontCompressPath

  - by Andrew Arnott

  When the .NET System.Uri class parses strings it performs some normalization on the input, such as lower-casing the scheme and hostname. It also trims trailing periods from each path segment. This latter feature is fatal to OpenID applications because some OpenIDs (like those issued from Yahoo) include base64 encoded path segments which may end with a period. How can I disable this period-trimming behavior of the Uri class? Registering my own scheme using UriParser.Register with a parser initialized with GenericUriParserOptions.DontCompressPath avoids the period trimming, and some other operations that are also undesirable for OpenID. But I cannot register a new parser for existing schemes like HTTP and HTTPS, which I must do for OpenIDs. Another approach I tried was registering my own new scheme, and programming the custom parser to change the scheme back to the standard HTTP(s) schemes as part of parsing: public class MyUriParser : GenericUriParser { private string actualScheme; public MyUriParser(string actualScheme) : base(GenericUriParserOptions.DontCompressPath) { this.actualScheme = actualScheme.ToLowerInvariant(); } protected override string GetComponents(Uri uri, UriComponents components, UriFormat format) { string result = base.GetComponents(uri, components, format); // Substitute our actual desired scheme in the string if it's in there. if ((components & UriComponents.Scheme) != 0) { string registeredScheme = base.GetComponents(uri, UriComponents.Scheme, format); result = this.actualScheme + result.Substring(registeredScheme.Length); } return result; } } class Program { static void Main(string[] args) { UriParser.Register(new MyUriParser("http"), "httpx", 80); UriParser.Register(new MyUriParser("https"), "httpsx", 443); Uri z = new Uri("httpsx://me.yahoo.com/b./c.#adf"); var req = (HttpWebRequest)WebRequest.Create(z); req.GetResponse(); } } This actually almost works. The Uri instance reports https instead of httpsx everywhere -- except the Uri.Scheme property itself. That's a problem when you pass this Uri instance to the HttpWebRequest to send a request to this address. Apparently it checks the Scheme property and doesn't recognize it as 'https' because it just sends plaintext to the 443 port instead of SSL. I'm happy for any solution that: Preserves trailing periods in path segments in Uri.Path Includes these periods in outgoing HTTP requests. Ideally works with under ASP.NET medium trust (but not absolutely necessary).

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• The most efficient method of drawing multiple quads in OpenGL

  - by CPatton

  I'm not very keen with OpenGL and I was wondering if someone could give me some insight on this. I'm a 'seasoned' programmer, I've read the redbook about VBOs and the like, but I was wondering from a more experienced person about the best/most efficient way of achieving this. I've been producing this 2d tile-based game engine to be used in several projects. I have a class called "ScreenObject" which is mainly composed of a Dictionary<Point, Tile> The Point key is to show where to render the Tile on the screen, and the Tile contains one or more textures to be drawn at that point. This ScreenObject is where the tiles will be modified, deleted, added, etc.. My original method of drawing the tiles in the testing I've done was to iterate through the ScreenObject and draw each quad at each location separately. From what I've read, this is a massive waste of resources. It wasn't horribly slow in the testing, but after I've completed the animation classes and effect classes, I'm sure it would be extremely slow. And one last thing, if you wouldn't mind.. As I said before, the Tile class can contain multiple textures to be drawn at the Point location on the screen. I recognize possibly two options for me here. Either add a quad at that location for each texture to be drawn, or, somehow.. use a multiple texture for the same quad (if it's possible). Even if each tile contained one texture only, that would be 64 quads to be drawn on the screen. Most of the tiles will contain 2-5 textures, so the number of total quads would increase dramatically with this method. Would it be feasible to add a quad for each new texture, or am I ignoring a better way to do this? Just need some help understanding this if you don't mind :) I've tried to be as concise as possible, and I'd greatly appreciate any responses.. and even some criticism. Programming is often a learning process and one who develops seems to never stops learning. Thanks for your time.

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