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• Problem with Google Calendar API invocation at server side

  - by Raffo

  Hi guys, I have problems with the invocation of the Google Calendar API. I downloaded the library for java and I added as external JAR in eclipse the following files: gdata-core, gdata-calendar, gdata- calendar-meta, gdata-client-meta, gdata-client. Then, I created a the method as it follows: import com.google.gdata.client.calendar.CalendarService; import com.google.gdata.data.calendar.CalendarEntry; import com.google.gdata.data.calendar.CalendarFeed; import com.google.gwt.user.server.rpc.RemoteServiceServlet; public class GCalServImpl extends RemoteServiceServlet implements GCalServ { @Override public String RetrieveCalendars() { // TODO Auto-generated method stub // Create a CalenderService and authenticate try{ CalendarService myService = new CalendarService("taskR"); myService.setUserCredentials(***username***, "***password***"); // Send the request and print the response URL feedUrl = new URL("http://www.google.com/calendar/feeds/default/ allcalendars/full"); CalendarFeed resultFeed = myService.getFeed(feedUrl, CalendarFeed.class); System.out.println("Your calendars:"); System.out.println(); String s = ""; for (int i = 0; i < resultFeed.getEntries().size(); i++) { CalendarEntry entry = resultFeed.getEntries().get(i); s=entry.getTitle().getPlainText(); System.out.println("\t" + s); return s; } }catch(Exception e){ e.printStackTrace(); } return null; } I then call it from the client side doing a basic async invocation. If I try to launch the program I got the following errors: WARNING: Error for /taskr/cal java.lang.NoClassDefFoundError: com/google/gdata/client/calendar/ CalendarService at java.lang.Class.getDeclaredConstructors0(Native Method) at java.lang.Class.privateGetDeclaredConstructors(Class.java:2389) at java.lang.Class.getConstructor0(Class.java:2699) at java.lang.Class.newInstance0(Class.java:326) at java.lang.Class.newInstance(Class.java:308) at org.mortbay.jetty.servlet.Holder.newInstance(Holder.java:153) at org.mortbay.jetty.servlet.ServletHolder.initServlet(ServletHolder.java: 428) at org.mortbay.jetty.servlet.ServletHolder.getServlet(ServletHolder.java: 339) at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java: 487) at org.mortbay.jetty.servlet.ServletHandler $CachedChain.doFilter(ServletHandler.java:1166) at com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter(ServeBlobFilter.java: 51) at org.mortbay.jetty.servlet.ServletHandler $CachedChain.doFilter(ServletHandler.java:1157) at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java: 43) at org.mortbay.jetty.servlet.ServletHandler $CachedChain.doFilter(ServletHandler.java:1157) at com.google.appengine.tools.development.StaticFileFilter.doFilter(StaticFileFilter.java: 122) at org.mortbay.jetty.servlet.ServletHandler $CachedChain.doFilter(ServletHandler.java:1157) at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java: 388) at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java: 216) at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java: 182) at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java: 765) at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java: 418) at com.google.apphosting.utils.jetty.DevAppEngineWebAppContext.handle(DevAppEngineWebAppContext.java: 70) at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java: 152) at com.google.appengine.tools.development.JettyContainerService $ApiProxyHandler.handle(JettyContainerService.java:349) at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java: 152) at org.mortbay.jetty.Server.handle(Server.java:326) at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java: 542) at org.mortbay.jetty.HttpConnection $RequestHandler.content(HttpConnection.java:938) at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:755) at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:218) at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404) at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java: 409) at org.mortbay.thread.QueuedThreadPool $PoolThread.run(QueuedThreadPool.java:582) Caused by: java.lang.ClassNotFoundException: com.google.gdata.client.calendar.CalendarService at java.net.URLClassLoader$1.run(URLClassLoader.java:200) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:188) at java.lang.ClassLoader.loadClass(ClassLoader.java:315) at com.google.appengine.tools.development.IsolatedAppClassLoader.loadClass(IsolatedAppClassLoader.java: 151) at java.lang.ClassLoader.loadClass(ClassLoader.java:250) at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:398) ... 33 more What can I do??

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• I'm trying to handle the updates on 2 related tables in one DetailsView using Jquery and Linq, and h

  - by Ben Reisner

  Given two related tables (reports, report_fields) where there can be many report_fields entries for each reports entry, I need to allow the user to enter new report_fields, delete existing report_fields, and re-arrange the order. Currently I am using a DetailsView to handle the editing of the reports. I added some logic to handle report_fields, and currently it allows you to succesfully re-arrange the order, but i'm a little stumped as to the best way to add new items, or delete existing items. The basic logic I have is that each report_fields is represented by a . It has a description as the text, and a field for each field in the report_fields table. I use JQuery Sortable to allow the user to re-arrange the LIs. Abbreviated Create Table Statements:(foreign key constraint ignored for brevity) create table report( id integer primary key identity, reportname varchar(250) ) create table report_fields( id integer primary key identity, reportID integer, keyname integer, keyvalue integer, field_order integer ) My abbreviated markup: <asp:DetailsView ...> ... <asp:TemplateField HeaderText="Fields"> <EditItemTemplate> <ul class="MySortable"> <asp:Repeater ID="Repeater1" runat="server" DataSource='<%# Eval("report_fields") %>'> <ItemTemplate> <li> <%# Eval("keyname") %>: <%# Eval("keyvalue") %> <input type="hidden" name="keyname[]" value='<%# Eval("keyname") %>' /> <input type="hidden" name="keyvalue[]" value='<%# Eval("keyvalue") %>' /> </li> </ItemTemplate> </asp:Repeater> </ul> </EditItemTemplate> </asp:TemplateField> </asp:DetailsView> <asp:LinqDataSource ID="LinqDataSource2" onupdating="LinqDataSource2_Updating" table=reports ... /> $(function() { $(".MySortable").sortable({ placeholder: 'MySortable-highlight' }).disableSelection(); }); Code Behind Class: public partial class Administration_AddEditReport protected void LinqDataSource2_Updating(object sender, LinqDataSourceUpdateEventArgs e) { report r = (report)e.NewObject; MyDataContext dc = new MyDataContext(); var fields = from f in dc.report_fields where f.reportID == r.id select f; dc.report_fields.DeleteAllOnSubmit(fields); NameValueCollection nvc = Request.Params; string[] keyname = nvc["keyname[]"].Split(','); string[] keyvalue = nvc["keyvalue[]"].Split(','); for (int i = 0; i < keyname.Length; i++) { report_field rf = new report_field(); rf.reportID = r.id; rf.keyname = keyname[i]; rf.keyvalue = keyvalue[i]; rf.field_order = i; dc.report_fields.InsertOnSubmit(rf); } dc.SubmitChanges(); } }

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• AES BYTE SYSTOLIC ARCHITECTURE.

  - by anum

  we are implementing AES BYTE SYSTOLIC ARCHITECTURE. CODE:- module key_expansion(kld,clk,key,key_expand,en); input kld,clk,en; input [127:0] key; wire [31:0] w0,w1,w2,w3; output [127:0] key_expand; reg[127:0] key_expand; reg [31:0] w[3:0]; reg [3:0] ctr; //reg [31:0] w0,w1,w2,w3; wire [31:0] c0,c1,c2,c3; wire [31:0] tmp_w; wire [31:0] subword; wire [31:0] rcon; assign w0 = w[0]; assign w1 = w[1]; assign w2 = w[2]; assign w3 = w[3]; //always @(posedge clk) always @(posedge clk) begin w[0] <= #1 kld ? key[127:096] : w[0]^subword^rcon; end always @(posedge clk) begin w[1] <= #1 kld ? key[095:064] : w[0]^w[1]^subword^rcon; end always @(posedge clk) begin w[2] <= #1 kld ? key[063:032] : w[0]^w[2]^w[1]^subword^rcon; end always @(posedge clk) begin w[3] <= #1 kld ? key[031:000] : w[0]^w[3]^w[2]^w[1]^subword^rcon; end assign tmp_w = w[3]; aes_sbox u0( .a(tmp_w[23:16]), .d(subword[31:24])); aes_sbox u1( .a(tmp_w[15:08]), .d(subword[23:16])); aes_sbox u2( .a(tmp_w[07:00]), .d(subword[15:08])); aes_sbox u3( .a(tmp_w[31:24]), .d(subword[07:00])); aes_rcon r0( .clk(clk), .kld(kld), .out_rcon(rcon)); //assign key_expand={w0,w1,w2,w3}; //assign key_expand={w0,w1,w2,w3}; always@(posedge clk) begin if (!en) begin ctr<=0; end else if (|ctr) begin key_expand<=0; ctr<=(ctr+1)%16; end else if (!(|ctr)) begin key_expand<={w0,w1,w2,w3}; ctr<=(ctr+1)%16; end end endmodule problem:verilog code has been attached THE BASIC problem is that we want to generate a new key after 16 clock cycles.whereas initially it would generate a new key every posedge of clock.in order to stop the value from being assigned to w[0] w[1] w[2] w[3] we implemented an enable counter logic as under.it has enabled us to give output in key_expand after 16 cycles but the value of required keys has bin changed.because the key_expand takes up the latest value from w[0],w[1],w[2],w[3] where as we require the first value generated.. we should block the value to be assigned to w[0] to w[3] somehow ..but we are stuck.plz help.

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• Is it possible to call Javascript's onsubmit event programatically on a form?

  - by hoyhoy

  In Ruby on Rails, I'm attempting to update the innerHTML of a div tag using the form_remote_tag helper. This update happens whenever an associated select tag receives an onchange event. The problem is, <select onchange="this.form.submit();">; doesn't work. Nor does document.forms[0].submit(). The only way to get the onsubmit code generated in the form_remote_tag to execute is to create a hidden submit button, and invoke the click method on the button from the select tag. Here's a working ERb partial example. <% form_remote_tag :url => product_path, :update => 'content', :method => 'get' do -%> <% content_tag :div, :id => 'content' do -%> <%= select_tag :update, options_for_select([["foo", 1], ["bar", 2]]), :onchange => "this.form.commit.click" %> <%= submit_tag 'submit_button', :style => "display: none" %> <% end %> <% end %> What I want to do is something like this, but it doesn't work. <% form_remote_tag :url => product_path, :update => 'content', :method => 'get' do -%> <% content_tag :div, :id => 'content' do -%> # the following line does not work <%= select_tag :update, options_for_select([["foo", 1], ["bar", 2]]), :onchange => "this.form.onsubmit()" %> <% end %> <% end %> So, is there any way to remove the invisible submit button for this use case? There seems to be some confusion. So, let me explain. The basic problem is that submit() doesn't call the onsubmit() code rendered into the form. The actual HTML form that Rails renders from this ERb looks like this: <form action="/products/1" method="post" onsubmit="new Ajax.Updater('content', '/products/1', {asynchronous:true, evalScripts:true, method:'get', parameters:Form.serialize(this)}); return false;"> <div style="margin:0;padding:0"> <input name="authenticity_token" type="hidden" value="4eacf78eb87e9262a0b631a8a6e417e9a5957cab" /> </div> <div id="content"> <select id="update" name="update" onchange="this.form.commit.click"> <option value="1">foo</option> <option value="2">bar</option> </select> <input name="commit" style="display: none" type="submit" value="submit_button" /> </div> </form> I want to axe the invisible submit button, but using a straight form.submit appears to not work. So, I need some way to call the form's onsubmit event code. Update: Orion Edwards solution would work if there wasn't a return(false); generated by Rails. I'm not sure which is worse though, sending a phantom click to an invisible submit button or calling eval on the getAttribute('onsubmit') call after removing the return call with a javascript string replacement!

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• Why isn't my algorithm for find the biggest and smallest inputs working?

  - by Matt Ellen

  I have started a new job, and with it comes a new language: Ironpython. Thankfully a good language :D Before starting I got to grips with Python on the whole, but that was only a week's worth of learning. Now I'm writing actual code. I've been charged with writing an algorithm that finds the best input parameter to collect data with. The basic algorithm is (as I've been instructed): Set the input parameter to a good guess Start collecting data When data is available stop collecting find the highest point If the point before this (i.e. for the previous parameter value) was higher and the point before that was lower then we've found the max otherwise the input parameter is increased by the initial guess. goto 2 If the max is found then the min needs to be found. To do this the algorithm carries on increasing the input, but by 1/10 of the max, until the current point is greater than the previous point and the point before that is also greater. Once the min is found then the algorithm stops. Currently I have a simplified data generator outputting the sin of the input, so that I know that the min value should be PI and the max value should be PI/2 The main Python code looks like this (don't worry, this is just for my edification, I don't write real code like this): import sys sys.path.append(r"F:\Programming Source\C#\PythonHelp\PythonHelp\bin\Debug") import clr clr.AddReferenceToFile("PythonHelpClasses.dll") import PythonHelpClasses from PHCStruct import Helper from System import Math helper = Helper() def run(): b = PythonHelpClasses.Executor() a = PythonHelpClasses.HasAnEvent() b.Input = 0.0 helper.__init__() def AnEventHandler(e): b.Stop() h = helper h.lastLastVal, h.lastVal, h.currentVal = h.lastVal, h.currentVal, e.Number if h.lastLastVal < h.lastVal and h.currentVal < h.lastVal and h.NotPast90: h.NotPast90 = False h.bestInput = h.lastInput inputInc = 0.0 if h.NotPast90: inputInc = Math.PI/10.0 else: inputInc = h.bestInput/10.0 if h.lastLastVal > h.lastVal and h.currentVal > h.lastVal and h.NotPast180: h.NotPast180 = False if h.NotPast180: h.lastInput, b.Input = b.Input, b.Input + inputInc b.Start(a) else: print "Best input:", h.bestInput print "Last input:", h.lastInput b.Stop() a.AnEvent += AnEventHandler b.Start(a) PHCStruct.py: class Helper(): def __init__(self): self.currentVal = 0 self.lastVal = 0 self.lastLastVal = 0 self.NotPast90 = True self.NotPast180 = True self.bestInput = 0 self.lastInput = 0 PythonHelpClasses has two small classes I wrote in C# before I realised how to do it in Ironpython. Executor runs a delegate asynchronously while it's running member is true. The important code: public void Start(HasAnEvent hae) { running = true; RunDelegate r = new RunDelegate(hae.UpdateNumber); AsyncCallback ac = new AsyncCallback(UpdateDone); IAsyncResult ar = r.BeginInvoke(Input, ac, null); } public void Stop() { running = false; } public void UpdateDone(IAsyncResult ar) { RunDelegate r = (RunDelegate)((AsyncResult)ar).AsyncDelegate; r.EndInvoke(ar); if (running) { AsyncCallback ac = new AsyncCallback(UpdateDone); IAsyncResult ar2 = r.BeginInvoke(Input, ac, null); } } HasAnEvent has a function that generates the sin of its input and fires an event with that result as its argument. i.e.: public void UpdateNumber(double val) { AnEventArgs e = new AnEventArgs(Math.Sin(val)); System.Threading.Thread.Sleep(1000); if (null != AnEvent) { AnEvent(e); } } The sleep is in there just to slow things down a bit. The problem I am getting is that the algorithm is not coming up with the best input being PI/2 and the final input being PI, but I can't see why. Also the best and final inputs are different each time I run the programme. Can anyone see why? Also when the algorithm terminates the best and final inputs are printed to the screen multiple times, not just once. Can someone explain why?

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• Javascript Closures - What are the negatives?

  - by vol7ron

  Question: There seem to be many benefits to Closures, but what are the negatives (memory leakage? obfuscation problems? bandwidth increasage?)? Additionally, is my understanding of Closures correct? Finally, once closures are created, can they be destroyed? I've been reading a little bit about Javascript Closures. I hope someone a little more knowledgeable will guide my assertions, correcting me where wrong. Benefits of Closures: Encapsulate the variables to a local scope, by using an internal function. The anonymity of the function is insignificant. What I've found helpful is to do some basic testing, regarding local/global scope: <script type="text/javascript"> var global_text = ""; var global_count = 0; var global_num1 = 10; var global_num2 = 20; var global_num3 = 30; function outerFunc() { var local_count = local_count || 0; alert("global_num1: " + global_num1); // global_num1: undefined var global_num1 = global_num1 || 0; alert("global_num1: " + global_num1); // global_num1: 0 alert("global_num2: " + global_num2); // global_num2: 20 global_num2 = global_num2 || 0; // (notice) no definition with 'var' alert("global_num2: " + global_num2); // global_num2: 20 global_num2 = 0; alert("local_count: " + local_count); // local_count: 0 function output() { global_num3++; alert("local_count: " + local_count + "\n" + "global_count: " + global_count + "\n" + "global_text: " + global_text ); local_count++; } local_count++; global_count++; return output; } var myFunc = outerFunc(); myFunc(); /* Outputs: ********************** * local_count: 1 * global_count: 1 * global_text: **********************/ global_text = "global"; myFunc(); /* Outputs: ********************** * local_count: 2 * global_count: 1 * global_text: global **********************/ var local_count = 100; myFunc(); /* Outputs: ********************** * local_count: 3 * global_count: 1 * global_text: global **********************/ alert("global_num1: " + global_num1); // global_num1: 10 alert("global_num2: " + global_num2); // global_num2: 0 alert("global_num3: " + global_num3); // global_num3: 33 </script> Interesting things I took out of it: The alerts in outerFunc are only called once, which is when the outerFunc call is assigned to myFunc (myFunc = outerFunc()). This assignment seems to keep the outerFunc open, in what I would like to call a persistent state. Everytime myFunc is called, the return is executed. In this case, the return is the internal function. Something really interesting is the localization that occurs when defining local variables. Notice the difference in the first alert between global_num1 and global_num2, even before the variable is trying to be created, global_num1 is considered undefined because the 'var' was used to signify a local variable to that function. -- This has been talked about before, in the order of operation for the Javascript engine, it's just nice to see this put to work. Globals can still be used, but local variables will override them. Notice before the third myFunc call, a global variable called local_count is created, but it as no effect on the internal function, which has a variable that goes by the same name. Conversely, each function call has the ability to modify global variables, as noticed by global_var3. Post Thoughts: Even though the code is straightforward, it is cluttered by alerts for you guys, so you can plug and play. I know there are other examples of closures, many of which use anonymous functions in combination with looping structures, but I think this is good for a 101-starter course to see the effects. The one thing I'm concerned with is the negative impact closures will have on memory. Because it keeps the function environment open, it is also keeping those variables stored in memory, which may/may not have performance implications, especially regarding DOM traversals and garbage collection. I'm also not sure what kind of role this will play in terms of memory leakage and I'm not sure if the closure can be removed from memory by a simple "delete myFunc;." Hope this helps someone, vol7ron

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• Covariance and Contravariance in C#

  - by edalorzo

  I will start by saying that I am Java developer learning to program in C#. As such I do comparisons of what I know with what I am learning. I have been playing with C# generics for a few hours now, and I have been able to reproduce the same things I know in Java in C#, with the exception of a couple of examples using covariance and contravariance. The book I am reading is not very good in the subject. I will certainly seek more info on the web, but while I do that, perhaps you can help me find a C# implementation for the following Java code. An example is worth a thousand words, and I was hoping that by looking a good code sample I will be able to assimilate this more rapidly. Covariance In Java I can do something like this: public static double sum(List<? extends Number> numbers) { double summation = 0.0; for(Number number : numbers){ summation += number.doubleValue(); } return summation; } I can use this code as follows: List<Integer> myInts = asList(1,2,3,4,5); List<Double> myDoubles = asList(3.14, 5.5, 78.9); List<Long> myLongs = asList(1L, 2L, 3L); double result = 0.0; result = sum(myInts); result = sum(myDoubles) result = sum(myLongs); Now I did discover that C# supports covariance/contravariance only on interfaces and as long as they have been explicitly declared to do so (out). I think I was not able to reproduce this case, because I could not find a common ancestor of all numbers, but I believe that I could have used IEnumerable to implement such thing if a common ancestor exists. Since IEnumerable is a covariant type. Right? Any thoughts on how to implement the list above? Just point me into the right direction. Is there any common ancestor of all numeric types? Contravariance The contravariance example I tried was the following. In Java I can do this to copy one list into another. public static void copy(List<? extends Number> source, List<? super Number> destiny){ for(Number number : source) { destiny.add(number); } } Then I could use it with contravariant types as follows: List<Object> anything = new ArrayList<Object>(); List<Integer> myInts = asList(1,2,3,4,5); copy(myInts, anything); My basic problem, trying to implement this in C# is that I could not find an interface that was both covariant and contravariant at the same time, as it is case of List in my example above. Maybe it can be done with two different interface in C#. Any thoughts on how to implement this? Thank you very much to everyone for any answers you can contribute. I am pretty sure I will learn a lot from any example you can provide.

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• Dynamically specify the type in C#

  - by Lirik

  I'm creating a custom DataSet and I'm under some constrains: I want the user to specify the type of the data which they want to store. I want to reduce type-casting because I think it will be VERY expensive. I will use the data VERY frequently in my application. I don't know what type of data will be stored in the DataSet, so my initial idea was to make it a List of objects, but I suspect that the frequent use of the data and the need to type-cast will be very expensive. The basic idea is this: class DataSet : IDataSet { private Dictionary<string, List<Object>> _data; /// <summary> /// Constructs the data set given the user-specified labels. /// </summary> /// <param name="labels"> /// The labels of each column in the data set. /// </param> public DataSet(List<string> labels) { _data = new Dictionary<string, List<object>>(); foreach (string label in labels) { _data.Add(label, new List<object>()); } } #region IDataSet Members public List<string> DataLabels { get { return _data.Keys.ToList(); } } public int Count { get { _data[_data.Keys[0]].Count; } } public List<object> GetValues(string label) { return _data[label]; } public object GetValue(string label, int index) { return _data[label][index]; } public void InsertValue(string label, object value) { _data[label].Insert(0, value); } public void AddValue(string label, object value) { _data[label].Add(value); } #endregion } A concrete example where the DataSet will be used is to store data obtained from a CSV file where the first column contains the labels. When the data is being loaded from the CSV file I'd like to specify the type rather than casting to object. The data could contain columns such as dates, numbers, strings, etc. Here is what it could look like: "Date","Song","Rating","AvgRating","User" "02/03/2010","Code Monkey",4.6,4.1,"joe" "05/27/2009","Code Monkey",1.2,4.5,"jill" The data will be used in a Machine Learning/Artificial Intelligence algorithm, so it is essential that I make the reading of data very fast. I want to eliminate type-casting as much as possible, since I can't afford to cast from 'object' to whatever data type is needed on every read. I've seen applications that allow the user to pick the specific data type for each item in the csv file, so I'm trying to make a similar solution where a different type can be specified for each column. I want to create a generic solution so I don't have to return a List<object> but a List<DateTime> (if it's a DateTime column) or List<double> (if it's a column of doubles). Is there any way that this can be achieved? Perhaps my approach is wrong, is there a better approach to this problem?

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• Use QuickCheck by generating primes

  - by Dan

  Background For fun, I'm trying to write a property for quick-check that can test the basic idea behind cryptography with RSA. Choose two distinct primes, p and q. Let N = p*q e is some number relatively prime to (p-1)(q-1) (in practice, e is usually 3 for fast encoding) d is the modular inverse of e modulo (p-1)(q-1) For all x such that 1 < x < N, it is always true that (x^e)^d = x modulo N In other words, x is the "message", raising it to the eth power mod N is the act of "encoding" the message, and raising the encoded message to the dth power mod N is the act of "decoding" it. (The property is also trivially true for x = 1, a case which is its own encryption) Code Here are the methods I have coded up so far: import Test.QuickCheck -- modular exponentiation modExp :: Integral a => a -> a -> a -> a modExp y z n = modExp' (y `mod` n) z `mod` n where modExp' y z | z == 0 = 1 | even z = modExp (y*y) (z `div` 2) n | odd z = (modExp (y*y) (z `div` 2) n) * y -- relatively prime rPrime :: Integral a => a -> a -> Bool rPrime a b = gcd a b == 1 -- multiplicative inverse (modular) mInverse :: Integral a => a -> a -> a mInverse 1 _ = 1 mInverse x y = (n * y + 1) `div` x where n = x - mInverse (y `mod` x) x -- just a quick way to test for primality n `divides` x = x `mod` n == 0 primes = 2:filter isPrime [3..] isPrime x = null . filter (`divides` x) $ takeWhile (\y -> y*y <= x) primes -- the property prop_rsa (p,q,x) = isPrime p && isPrime q && p /= q && x > 1 && x < n && rPrime e t ==> x == (x `powModN` e) `powModN` d where e = 3 n = p*q t = (p-1)*(q-1) d = mInverse e t a `powModN` b = modExp a b n (Thanks, google and random blog, for the implementation of modular multiplicative inverse) Question The problem should be obvious: there are way too many conditions on the property to make it at all usable. Trying to invoke quickCheck prop_rsa in ghci made my terminal hang. So I've poked around the QuickCheck manual a bit, and it says: Properties may take the form forAll <generator> $ \<pattern> -> <property> How do I make a <generator> for prime numbers? Or with the other constraints, so that quickCheck doesn't have to sift through a bunch of failed conditions? Any other general advice (especially regarding QuickCheck) is welcome.

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• .NET Programmatically invoke screenclick doesn't work?

  - by ropstah

  I'm trying to programmatically invoke an onclick event however the click is not received/handled. Am I missing something, or is security preventing the click to be executed? I have a forms application which is invisible. Basically I would like to say: DoDoubleClick(wait, x, y) This should raise two click (mousedown+mouseup) events on screen with the specified wait interval. However the click isn't received in a Flash application in Firefox (which is running at that moment). Here's my code: Form: Public Class Form1 Private WithEvents gmh As GlobalMouseHook Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load gmh = New GlobalMouseHook() Me.Visible = false gmh.DoDoubleClick(50, 800, 600) End Sub Private Sub Form1_FormClosed(ByVal sender As System.Object, ByVal e As System.Windows.Forms.FormClosedEventArgs) Handles MyBase.FormClosed gmh.Dispose() End Sub Private Sub gmh_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles gmh.MouseDown End Sub Private Sub gmh_MouseMove(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles gmh.MouseMove End Sub Private Sub gmh_MouseUp(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles gmh.MouseUp End Sub End Class GlobalMouseHook class: Friend Class GlobalMouseHook Implements IDisposable Private hhk As IntPtr = IntPtr.Zero Private disposedValue As Boolean = False Public Event MouseDown As MouseEventHandler Public Event MouseUp As MouseEventHandler Public Event MouseMove As MouseEventHandler Public Sub New() Hook() End Sub Private Sub Hook() Dim hInstance As IntPtr = LoadLibrary("User32") hhk = SetWindowsHookEx(WH_MOUSE_LL, AddressOf Me.HookProc, hInstance, 0) End Sub Private Sub Unhook() UnhookWindowsHookEx(hhk) End Sub Public Sub DoDoubleClick(ByVal wait As Integer, ByVal x As Integer, ByVal y As Integer) RaiseEvent MouseDown(Me, New MouseEventArgs(MouseButtons.Left, 1, x, y, 0)) RaiseEvent MouseUp(Me, Nothing) System.Threading.Thread.Sleep(wait) RaiseEvent MouseDown(Me, New MouseEventArgs(MouseButtons.Left, 1, x, y, 0)) RaiseEvent MouseUp(Me, Nothing) End Sub Private Function HookProc(ByVal nCode As Integer, ByVal wParam As UInteger, ByRef lParam As MSLLHOOKSTRUCT) As Integer If nCode >= 0 Then Select Case wParam Case WM_LBUTTONDOWN RaiseEvent MouseDown(Me, New MouseEventArgs(MouseButtons.Left, 0, lParam.pt.x, lParam.pt.y, 0)) Case WM_RBUTTONDOWN RaiseEvent MouseDown(Me, New MouseEventArgs(MouseButtons.Right, 0, lParam.pt.x, lParam.pt.y, 0)) Case WM_MBUTTONDOWN RaiseEvent MouseDown(Me, New MouseEventArgs(MouseButtons.Middle, 0, lParam.pt.x, lParam.pt.y, 0)) Case WM_LBUTTONUP, WM_RBUTTONUP, WM_MBUTTONUP RaiseEvent MouseUp(Nothing, Nothing) Case WM_MOUSEMOVE RaiseEvent MouseMove(Nothing, Nothing) Case WM_MOUSEWHEEL, WM_MOUSEHWHEEL Case Else Console.WriteLine(wParam) End Select End If Return CallNextHookEx(hhk, nCode, wParam, lParam) End Function Private Structure API_POINT Public x As Integer Public y As Integer End Structure Private Structure MSLLHOOKSTRUCT Public pt As API_POINT Public mouseData As UInteger Public flags As UInteger Public time As UInteger Public dwExtraInfo As IntPtr End Structure Private Const WM_MOUSEWHEEL As UInteger = &H20A Private Const WM_MOUSEHWHEEL As UInteger = &H20E Private Const WM_MOUSEMOVE As UInteger = &H200 Private Const WM_LBUTTONDOWN As UInteger = &H201 Private Const WM_LBUTTONUP As UInteger = &H202 Private Const WM_MBUTTONDOWN As UInteger = &H207 Private Const WM_MBUTTONUP As UInteger = &H208 Private Const WM_RBUTTONDOWN As UInteger = &H204 Private Const WM_RBUTTONUP As UInteger = &H205 Private Const WH_MOUSE_LL As Integer = 14 Private Delegate Function LowLevelMouseHookProc(ByVal nCode As Integer, ByVal wParam As UInteger, ByRef lParam As MSLLHOOKSTRUCT) As Integer Private Declare Auto Function LoadLibrary Lib "kernel32" (ByVal lpFileName As String) As IntPtr Private Declare Auto Function SetWindowsHookEx Lib "user32.dll" (ByVal idHook As Integer, ByVal lpfn As LowLevelMouseHookProc, ByVal hInstance As IntPtr, ByVal dwThreadId As UInteger) As IntPtr Private Declare Function CallNextHookEx Lib "user32" (ByVal hhk As IntPtr, ByVal nCode As Integer, ByVal wParam As UInteger, ByRef lParam As MSLLHOOKSTRUCT) As Integer Private Declare Function UnhookWindowsHookEx Lib "user32" (ByVal hhk As IntPtr) As Boolean ' IDisposable Protected Overridable Sub Dispose(ByVal disposing As Boolean) If Not Me.disposedValue Then If disposing Then ' TODO: free other state (managed objects). End If Unhook() End If Me.disposedValue = True End Sub ' This code added by Visual Basic to correctly implement the disposablepattern. Public Sub Dispose() Implements IDisposable.Dispose ' Do not change this code. Put cleanup code in Dispose(ByValdisposing As Boolean) above. Dispose(True) GC.SuppressFinalize(Me) End Sub End Class

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• can you simlify and generalize this useful jQuery function?

  - by user199368

  Hi, I'm doing an eshop with goods displayed as "tiles" in grid as usual. I just want to use various sizes of tiles and make sure (via jQuery) there are no free spaces. In basic situation, I have a 960px wrapper and want to use 240x180px (class .grid_4) tiles and 480x360px (class .grid_8) tiles. See image (imagine no margins/paddings there): Problems without jQuery: - when the CMS provides the big tile as 6th, there would be a free space under the 5th one - when the CMS provides the big tile as 7th, there would be a free space under 5th and 6th - when the CMS provides the big tile as 8th, it would shift to next line, leaving position no.8 free My solution so far looks like this: $(".grid_8").each(function(){ //console.log("BIG on position "+($(this).index()+1)+" which is "+(($(this).index()+1)%2?"ODD":"EVEN")); switch (($(this).index()+1)%4) { case 1: // nothing needed //console.log("case 1"); break; case 2: //need to shift one position and wrap into 240px div //console.log("case 2"); $(this).insertAfter($(this).next()); //swaps this with next $(this).prevAll(":nth(0), :nth(1)").wrapAll("<div class=\"grid_4\" />"); break; case 3: //need to shift two positions and wrap into 480px div //console.log("case 3"); $(this).prevAll(":nth(0), :nth(1)").wrapAll("<div class=\"grid_4\" />"); //wraps previous two - forcing them into column $(this).nextAll(":nth(0), :nth(1)").wrapAll("<div class=\"grid_4\" />"); //wraps next two - forcing them into column $(this).insertAfter($(this).next()); //moves behind the second column break; case 0: //need to shift one position //console.log("case 4"); $(this).insertAfter($(this).next()); //console.log("shifted to next line"); break; } }); It should be obvious from the comments how it works - generally always makes sure that the big tile is on odd position (count of preceding small tiles is even) by shifting one position back if needed. Also small tiles to the left from the big one need to be wrapped in another div so that they appear in column rather than row. Now finally the questions: how to generalize the function so that I can use even more tile dimensions like 720x360 (3x2), 480x540 (2x3), etc.? is there a way to simplify the function? I need to make sure that big tile counts as a multiple of small tiles when checking the actual position. Because using index() on the tile on position 12 (last tile in 3rd row) would now return 7 (position 8) because tiles on positions 5 and 9 are wrapped together in one culumn and the big tile is also just a single div, but spans 2x2 positions. any clean way to ensure this? Thank you very much for any hints. Feel free to reuse the code, I think it can be useful. Josef

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• Selective emboldeing of text in a webpage

  - by Eknath Iyer

  while printing out utf-8 characters onto a webpage, if encapsulate them with they get emboldened, but anything else, the page turns blank. Why? def main(): print "Content-type: text/html\r\n\r\n"; print '<html>' print '<head>' print '<style type="text/css">' print '.highlight { background-color: yellow }' print '.color1 { color: green; }' print '.color2 { color: blue; }' print '.color3 { color: purple; }' print '.color4 { color: red; }' print '.color5 { color: teal; }' print '.color6 { color: yellow; }' print '.color7 { color: orange; }' print '.color8 { color: violet; }' print '</style></head>' print '<body>' form = cgi.FieldStorage() ch = form.getvalue('choice') if ch == 'English': in_sent = form.getvalue('f1') in_sent = in_sent.lower() cho=0 elif ch == 'Hindi': in_sent = trans_he(form.getvalue('transl1').decode("utf-8")).strip() cho=1 #cho = 0 for english #cho = 1 for hindi adict=[] print '<center><u> User Input Sentence ==> <b>', in_sent,'</b></u></center><br>' in_sent=in_sent.strip().split(' ') colordict={} counter=1 for word in in_sent: colordict[word]=counter counter = counter + 1 f = open('bidirectional.alignment.txt','rb').read() records=f.strip().split('\n\n\n') for record in records: el=[] el2 = [] #basic file processing is done here. record = record.strip().split('\n') source = record[cho] target = record[(cho+1)%2] source_sent = source.split(' # ')[1] target_sent = target.split(' # ')[1] source_words = source_sent.strip().split(' ') target_words = target_sent.strip().split(' ') trans_index = source.split(' # ')[2].strip().split(' ') for word in in_sent: if word in source_words: if int(trans_index[source_words.index(word)]) > 0: tword=target_words[(int(trans_index[source_words.index(word)])-1)] target_sent = target_sent.replace(tword+' ','<b>'+tword+' </b>') # When the <b> tag is used here(for the 'target_sent = ...' statement). it is fine. But when <b> is replaced by something like in the next line or even <i> or <u>, it doesn't show an output at all source_sent = source_sent.replace(word+' ','<span class="color1">'+word+' </span>') el2.append(source_sent) el2.append(target_sent) el.append(target_sent.count('<b>')) el.append(el2) if target_sent.count('<b>') > 0: adict.append(el) print '<table><tr><td><center><h1>SOURCE LANGUAGE</h1></center></td><td><center> <h1>TARGET LANGUAGE</h1></center></td></tr>' for entry in adict: print '<tr><td>',entry[1][0],'</td><td>',trans_eh(entry[1][1]).encode("utf-8"),'</td> </tr>' print '</table></body>' print '</html>' main()

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• Ruby on Rails is complaining about a method that doesn't exist that is built into Active Record. Wha

  - by grg-n-sox

  This will probably just be a simple problem and I am just blind or an idiot but I could use some help. So I am going over some basic guides in Rails, reviewing the basics and such for an upcoming exam. One of the guides included was the sort-of-standard getting started guide over at guide.rubyonrails.org. Here is the link if you need it. Also all my code is for my app is from there, so I have no problem releasing any of my code since it should be the same as shown there. I didn't do a copy paste, but I basically was typing with Vim in one half of my screen and the web page in the other half, typing what I see. http://guides.rubyonrails.org/getting_started.html So like I said, I am going along the guide when I noticed past a certain point in the tutorial, I was always getting an error on the site. To find the section of code, just hit Ctrl+f on the page (or whatever you have search/find set to) and enter "accepts_". This should immediately direct you to this chunk of code. class Post < ActiveRecord::Base validates_presence_of :name, :title validates_length_of :title, :minimum => 5 has_many :comments has_many :tags accepts_nested_attributes_for :tags, :allow_destroy => :true , :reject_if => proc { |attrs| attrs.all? { |k, v| v.blank? } } end So I tried putting this in my code. It is in ~/Rails/blog/app/models/post.rb in case you are wondering. However, even after all the other code I put in past that in the guide, hoping I was just missing some line of code that would come up later in the guide. But nothing, same error every time. This is what I get. NoMethodError in PostsController#index undefined method `accepts_nested_attributes_for' for #<Class:0xb7109f98> /usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/base.rb:1833:in `method_missing' app/models/post.rb:7 app/controllers/posts_controller.rb:9:in `index' Request Parameters: None Response Headers: {"Content-Type"=>"", "cookie"=>[], "Cache-Control"=>"no-cache"} Now, I copied the above code from the guide. The two code sections I edited mentioned in the error message I will paste as is below. class PostsController < ApplicationController # GET /posts # GET /posts.xml before_filter :find_post, :only => [:show, :edit, :update, :destroy] def index @posts = Post.find(:all) # <= the line 9 referred to in error message respond_to do |format| format.html # index.html.erb format.xml { render :xml => @posts } end end class Post < ActiveRecord::Base validates_presence_of :name, :title validates_length_of :title, :minimum => 5 has_many :comments has_many :tags accepts_nested_attributes_for :tags, :allow_destroy => :true , # <= problem :reject_if => proc { |attrs| attrs.all? { |k, v| v.blank? } } end Also here is gem local gem list. I do note that they are a bit out of date, but the default Rails install any of the school machines (an environment likely for my exam) is basically 'gem install rails --version 2.2.2' and since they are windows machines, they come with all the normal windows ruby gems that comes with the ruby installer. However, I am running this off a Debian virtual machine of mine, but trying to set it up similarly and I figured the windows ruby gems wouldn't change anything in Rails. *** LOCAL GEMS *** actionmailer (2.2.2) actionpack (2.2.2) activerecord (2.2.2) activeresource (2.2.2) activesupport (2.2.2) gem_plugin (0.2.3) hpricot (0.8.2) linecache (0.43) log4r (1.1.7) ptools (1.1.9) rack (1.1.0) rails (2.2.2) rake (0.8.7) sqlite3-ruby (1.2.3) So any ideas on what the problem is? Thanks in advanced.

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• Function calls not working in my page

  - by Vivek Dragon

  I made an select menu that works with the google-font-Api. I made to function in JSBIN here is my work http://jsbin.com/ocutuk/18/ But when i made the copy of my code in a html page its not even loading the font names in page. i tried to make it work but still it is in dead end. This is my html code <!DOCTYPE html> <html> <head> <script src="http://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js"> </script> <meta charset=utf-8 /> <title>FONT API</title> <script> function SetFonts(fonts) { for (var i = 0; i < fonts.items.length; i++) { $('#styleFont') .append($("<option></option>") .attr("value", fonts.items[i].family) .text(fonts.items[i].family)); } } var script = document.createElement('script'); script.src = 'https://www.googleapis.com/webfonts/v1/webfonts?key=AIzaSyB8Ua6XIfe-gqbkE8P3XL4spd0x8Ft7eWo&callback=SetFonts'; document.body.appendChild(script); WebFontConfig = { google: { families: ['ABeeZee', 'Abel', 'Abril Fatface', 'Aclonica', 'Acme', 'Actor', 'Adamina', 'Advent Pro', 'Aguafina Script', 'Akronim', 'Aladin', 'Aldrich', 'Alegreya', 'Alegreya SC', 'Alex Brush', 'Alfa Slab One', 'Alice', 'Alike', 'Alike Angular', 'Allan', 'Allerta', 'Allerta Stencil', 'Allura', 'Almendra', 'Almendra Display', 'Almendra SC', 'Amarante', 'Amaranth', 'Amatic SC', 'Amethysta', 'Anaheim', 'Andada', 'Andika', 'Angkor', 'Annie Use Your Telescope', 'Anonymous Pro', 'Antic', 'Antic Didone', 'Antic Slab', 'Anton', 'Arapey', 'Arbutus', 'Arbutus Slab', 'Architects Daughter', 'Archivo Black', 'Archivo Narrow', 'Arimo', 'Arizonia', 'Armata', 'Artifika', 'Arvo', 'Asap', 'Asset', 'Astloch', 'Asul', 'Atomic Age', 'Aubrey', 'Audiowide', 'Autour One', 'Average', 'Average Sans', 'Averia Gruesa Libre', 'Averia Libre', 'Averia Sans Libre', 'Averia Serif Libre', 'Bad Script', 'Balthazar', 'Bangers', 'Basic', 'Battambang', 'Baumans', 'Bayon', 'Belgrano', 'Belleza', 'BenchNine', 'Bentham', 'Berkshire Swash', 'Bevan', 'Bigelow Rules', 'Bigshot One', 'Bilbo', 'Bilbo Swash Caps', 'Bitter', 'Black Ops One', 'Bokor', 'Bonbon', 'Boogaloo', 'Bowlby One', 'Bowlby One SC', 'Brawler', 'Bree Serif', 'Bubblegum Sans', 'Bubbler One', 'Buda', 'Buenard', 'Butcherman', 'Butterfly Kids', 'Cabin', 'Cabin Condensed', 'Cabin Sketch', 'Caesar Dressing', 'Cagliostro', 'Calligraffitti', 'Cambo', 'Candal', 'Cantarell', 'Cantata One', 'Cantora One', 'Capriola', 'Cardo', 'Carme', 'Carrois Gothic', 'Carrois Gothic SC', 'Carter One', 'Caudex', 'Cedarville Cursive', 'Ceviche One', 'Changa One', 'Chango', 'Chau Philomene One', 'Chela One', 'Chelsea Market', 'Chenla', 'Cherry Cream Soda', 'Cherry Swash', 'Chewy', 'Chicle', 'Chivo', 'Cinzel', 'Cinzel Decorative', 'Clicker Script', 'Coda', 'Coda Caption', 'Codystar', 'Combo', 'Comfortaa', 'Coming Soon', 'Concert One', 'Condiment', 'Content', 'Contrail One', 'Convergence', 'Cookie', 'Copse', 'Corben', 'Courgette', 'Cousine', 'Coustard', 'Covered By Your Grace', 'Crafty Girls', 'Creepster', 'Crete Round', 'Crimson Text', 'Croissant One', 'Crushed', 'Cuprum', 'Cutive', 'Cutive Mono']} }; (function() { var wf = document.createElement('script'); wf.src = ('https:' == document.location.protocol ? 'https' : 'http') + '://ajax.googleapis.com/ajax/libs/webfont/1/webfont.js'; wf.type = 'text/javascript'; wf.async = 'true'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(wf, s); })(); $("#styleFont").change(function (){ var id =$('#styleFont option' +':selected').val(); $("#custom_text").css('font-family',id); }); </script> <style> #custom_text { font-family: Arial; resize: none; margin-top: 20px; width: 500px; } #styleFont { width: 100px; } </style> </head> <body> <select id="styleFont"> </select><br> <textarea id="custom_text"></textarea> </body> </html> How can i make it work. Whats the mistake i am making here.

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• Losing sessions on GlassFish

  - by synti

  I have a web application that logs users in a @SessionScoped managed bean. It's all the basic stuff, pretty much like this: users logs in using regular http form and gets redirect to user area (wich is protected using a filter). But if any resource on that area is accessed, the request somehow uses a new session, wich has no managed bean, no user, and the filter does his job, redirecting him to login page. Here's the login form: <h:form> <h:outputLabel for="email" value="Email "/> <p:inputText id="email" size="30" value="#{loginManager.email}"/> <h:outputLabel for="password" value="Password "/> <p:password id="password" size="12" value="#{loginManager.password}"/> <p:commandButton value="Login" action="#{loginManager.login()}"/> </h:form> The loginManager managed bean: @ManagedBean @SessionScoped public class LoginManager implements Serializable { @EJB private UserService userService; private User user; private String email; private String password; public String login() { user = userService.findBy(email, password); if (user == null) { // FacesMessage stuff } else { return "/user/welcome.xhtml?faces-redirect=true"; } } public String logout() { FacesContext.getCurrentInstance().getExternalContext().invalidateSession(); return "/index.xhtml?faces-redirect=true"; } // Getters, setters (no setter for user) and serialVersionUID And then comes the filter that protects the user area: @WebFilter(urlPatterns="/user/*", displayName="UserFilter") public class UserFilter implements Filter { @Override public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { HttpSession session = ((HttpServletRequest)request).getSession(false); LoginManager loginManager = (LoginManager) session.getAttribute("loginManager"); if (loginManager == null || !loginManager.hasUser()) { HttpServletResponse resp = (HttpServletResponse) response; resp.sendRedirect("index.xhtml"); } final User user = loginManager.getUser(); if (user.isValid()) { chain.doFilter(request, response); } else { HttpServletResponse resp = (HttpServletResponse) response; resp.sendRedirect("index.xhtml"); } } The UserService is just a stateless EJB that handles persistence. Part of the JSF for user area: <h:form> <p:panelMenu> <p:submenu label="Items"> <p:menuitem value="Add item" action="#{userItens.addItems}" ajax="false"/> <p:menuitem value="My items" /> </p:submenu> </p:panelMenu> </h:form> And finally the userItens managed bean. @ManagedBean @RequestScoped public class UserItens { private User user; @PostConstruct private void init() { HttpSession session = (HttpSession) FacesContext.getCurrentInstance() .getExternalContext().getSession(false); LoginManager loginManager = (LoginManager) session.getAttribute("loginManager"); if (loginManager != null) user = loginManager.getUser(); } public String addItems() { // Doesn't get here. Seems like UserFilter comes first, doesn't find // an user and redirects. } I'm using glassfish and session timeout is now on 0.

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• DSP - Filtering in the frequency domain via FFT

  - by Trap

  I've been playing around a little with the Exocortex implementation of the FFT, but I'm having some problems. Whenever I modify the amplitudes of the frequency bins before calling the iFFT the resulting signal contains some clicks and pops, especially when low frequencies are present in the signal (like drums or basses). However, this does not happen if I attenuate all the bins by the same factor. Let me put an example of the output buffer of a 4-sample FFT: // Bin 0 (DC) FFTOut[0] = 0.0000610351563 FFTOut[1] = 0.0 // Bin 1 FFTOut[2] = 0.000331878662 FFTOut[3] = 0.000629425049 // Bin 2 FFTOut[4] = -0.0000381469727 FFTOut[5] = 0.0 // Bin 3, this is the first and only negative frequency bin. FFTOut[6] = 0.000331878662 FFTOut[7] = -0.000629425049 The output is composed of pairs of floats, each representing the real and imaginay parts of a single bin. So, bin 0 (array indexes 0, 1) would represent the real and imaginary parts of the DC frequency. As you can see, bins 1 and 3 both have the same values, (except for the sign of the Im part), so I guess bin 3 is the first negative frequency, and finally indexes (4, 5) would be the last positive frequency bin. Then to attenuate the frequency bin 1 this is what I do: // Attenuate the 'positive' bin FFTOut[2] *= 0.5; FFTOut[3] *= 0.5; // Attenuate its corresponding negative bin. FFTOut[6] *= 0.5; FFTOut[7] *= 0.5; For the actual tests I'm using a 1024-length FFT and I always provide all the samples so no 0-padding is needed. // Attenuate var halfSize = fftWindowLength / 2; float leftFreq = 0f; float rightFreq = 22050f; for( var c = 1; c < halfSize; c++ ) { var freq = c * (44100d / halfSize); // Calc. positive and negative frequency indexes. var k = c * 2; var nk = (fftWindowLength - c) * 2; // This kind of attenuation corresponds to a high-pass filter. // The attenuation at the transition band is linearly applied, could // this be the cause of the distortion of low frequencies? var attn = (freq < leftFreq) ? 0 : (freq < rightFreq) ? ((freq - leftFreq) / (rightFreq - leftFreq)) : 1; // Attenuate positive and negative bins. mFFTOut[ k ] *= (float)attn; mFFTOut[ k + 1 ] *= (float)attn; mFFTOut[ nk ] *= (float)attn; mFFTOut[ nk + 1 ] *= (float)attn; } Obviously I'm doing something wrong but can't figure out what. I don't want to use the FFT output as a means to generate a set of FIR coefficients since I'm trying to implement a very basic dynamic equalizer. What's the correct way to filter in the frequency domain? what I'm missing? Thanks in advance.

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• Why do I get a segmentation fault while redirecting sys.stdout to Tkinter.Text widget in Python?

  - by Brent Nash

  I'm in the process of building a GUI-based application with Python/Tkinter that builds on top of the existing Python bdb module. In this application, I want to silence all stdout/stderr from the console and redirect it to my GUI. To accomplish this purpose, I've written a specialized Tkinter.Text object (code at the end of the post). The basic idea is that when something is written to sys.stdout, it shows up as a line in the "Text" with the color black. If something is written to sys.stderr, it shows up as a line in the "Text" with the color red. As soon as something is written, the Text always scrolls down to view the most recent line. I'm using Python 2.6.1 at the moment. On Mac OS X 10.5, this seems to work great. I have had zero problems with it. On RedHat Enterprise Linux 5, however, I pretty reliably get a segmentation fault during the run of a script. The segmentation fault doesn't always occur in the same place, but it pretty much always occurs. If I comment out the sys.stdout= and sys.stderr= lines from my code, the segmentation faults seem to go away. I'm sure there are other ways around this that I will probably have to resort to, but can anyone see anything I'm doing blatantly wrong here that could be causing these segmentation faults? It's driving me nuts. Thanks! PS - I realize redirecting sys.stderr to the GUI might not be a great idea, but I still get segmentation faults even when I only redirect sys.stdout and not sys.stderr. I also realize that I'm allowing the Text to grow indefinitely at the moment. class ConsoleText(tk.Text): '''A Tkinter Text widget that provides a scrolling display of console stderr and stdout.''' class IORedirector(object): '''A general class for redirecting I/O to this Text widget.''' def __init__(self,text_area): self.text_area = text_area class StdoutRedirector(IORedirector): '''A class for redirecting stdout to this Text widget.''' def write(self,str): self.text_area.write(str,False) class StderrRedirector(IORedirector): '''A class for redirecting stderr to this Text widget.''' def write(self,str): self.text_area.write(str,True) def __init__(self, master=None, cnf={}, **kw): '''See the __init__ for Tkinter.Text for most of this stuff.''' tk.Text.__init__(self, master, cnf, **kw) self.started = False self.write_lock = threading.Lock() self.tag_configure('STDOUT',background='white',foreground='black') self.tag_configure('STDERR',background='white',foreground='red') self.config(state=tk.DISABLED) def start(self): if self.started: return self.started = True self.original_stdout = sys.stdout self.original_stderr = sys.stderr stdout_redirector = ConsoleText.StdoutRedirector(self) stderr_redirector = ConsoleText.StderrRedirector(self) sys.stdout = stdout_redirector sys.stderr = stderr_redirector def stop(self): if not self.started: return self.started = False sys.stdout = self.original_stdout sys.stderr = self.original_stderr def write(self,val,is_stderr=False): #Fun Fact: The way Tkinter Text objects work is that if they're disabled, #you can't write into them AT ALL (via the GUI or programatically). Since we want them #disabled for the user, we have to set them to NORMAL (a.k.a. ENABLED), write to them, #then set their state back to DISABLED. self.write_lock.acquire() self.config(state=tk.NORMAL) self.insert('end',val,'STDERR' if is_stderr else 'STDOUT') self.see('end') self.config(state=tk.DISABLED) self.write_lock.release()

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• Gridview delete/edit not working when using select parameter

  - by Brian Carroll

  new to ASP.NET. I created a sqldatasource and set up basic select query (SELECT * FROM Accounts) using the wizard. I then had the sqldatasource wizard create the INSERT, EDIT and DELETE queries. Connected this datasource to a gridview with EDITING and DELETING enabled. Everything works fine. The SELECT query returns all records and I can edit/delete them. Now I need to send a parameter to the SELECT command to filter the records to those with the user's id (pulled from Membership.GetUser). When I add this parameter, the SELECT command works fine, but the EDIT/DELETE buttons in the gridview no longer work. No error is generated. The page refreshes but the records were not updated in the database. I don't understand what is wrong. CODE: <% Dim u As MembershipUser Dim userid As String u = Membership.GetUser(User.Identity.Name) userid = u.ProviderUserKey.ToString SqlDataSource1.SelectParameters("UserId").DefaultValue = userid %> <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" DataKeyNames="ID" DataSourceID="SqlDataSource1"> <Columns> <asp:CommandField ShowDeleteButton="True" ShowEditButton="True" /> <asp:BoundField DataField="ID" HeaderText="ID" InsertVisible="False" ReadOnly="True" SortExpression="ID" /> <asp:BoundField DataField="UserId" HeaderText="UserId" SortExpression="UserId" /> <asp:BoundField DataField="AccountName" HeaderText="AccountName" SortExpression="AccountName" /> <asp:BoundField DataField="DateAdded" HeaderText="DateAdded" SortExpression="DateAdded" /> <asp:BoundField DataField="LastModified" HeaderText="LastModified" SortExpression="LastModified" /> </Columns> </asp:GridView> <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:CheckingConnectionString %>" DeleteCommand="DELETE FROM [Accounts] WHERE [ID] = @ID" InsertCommand="INSERT INTO [Accounts] ([UserId], [AccountName], [DateAdded], [LastModified]) VALUES (@UserId, @AccountName, @DateAdded, @LastModified)" SelectCommand="SELECT * FROM [Accounts] WHERE [UserId] = @UserId" UpdateCommand="UPDATE [Accounts] SET [UserId] = @UserId, [AccountName] = @AccountName, [DateAdded] = @DateAdded, [LastModified] = @LastModified WHERE [ID] = @ID"> <DeleteParameters> <asp:Parameter Name="ID" Type="Int32" /> </DeleteParameters> <InsertParameters> <asp:Parameter Name="UserId" Type="String" /> <asp:Parameter Name="AccountName" Type="String" /> <asp:Parameter Name="DateAdded" Type="DateTime" /> <asp:Parameter Name="LastModified" Type="DateTime" /> </InsertParameters> <UpdateParameters> <asp:Parameter Name="UserId" Type="String" /> <asp:Parameter Name="AccountName" Type="String" /> <asp:Parameter Name="DateAdded" Type="DateTime" /> <asp:Parameter Name="LastModified" Type="DateTime" /> <asp:Parameter Name="ID" Type="Int32" /> </UpdateParameters> <SelectParameters> <asp:Parameter Name="UserId"/> </SelectParameters> </asp:SqlDataSource>

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• Javascript works great locally, but not on my server

  - by Jonathan Cohen

  I'm teaching myself javascript by creating a script for displaying an external rss feed on a webpage. The code I patched together works great locally. This is a screen grab of the code producing exactly the desired behavior. The code is populating all the information inside the section "Blog: Shades of Gray", except for "tagged" which I hard coded: But when I upload the site files to my server, the code doesn't work at all. This is a screen grab of the code on my site NOT producing the desired behavior... This feels like I'm not getting something really basic about how javascript works locally vs. on the server. I did my half hour of googling for an answer and no trails look promising. So I'd really appreciate your help. This is my site (under construction) http://jonathangcohen.com Below is the code, which can also be found at http://jonathangcohen.com/grabFeeds.js. /*Javascript for Displaying an External RSS Feed on a Webpage Wrote some code that’ll grab attributes from an rss feed and assign IDs for displaying on a webpage. The code references my Tumblr blog but it’ll extend to any RSS feed.*/ window.onload = writeRSS; function writeRSS(){ writeBlog(); } function writeBlog(){ if (window.XMLHttpRequest) {// code for IE7+, Firefox, Chrome, Opera, Safari xmlhttp=new XMLHttpRequest(); } else {// code for IE6, IE5 xmlhttp=new ActiveXObject("Microsoft.XMLHTTP"); } xmlhttp.open("GET","http://blog.jonathangcohen.com/rss.xml",false); xmlhttp.send(); xmlDoc=xmlhttp.responseXML; var x=xmlDoc.getElementsByTagName("item"); //append category to link for (i=0;i<3;i++) { if (i == 0){ //print category var blogTumblrCategory = x[i].getElementsByTagName("category")[0].childNodes[0].nodeValue document.getElementById("getBlogCategory1").innerHTML = '<a class="BlogTitleLinkStyle" href="http://blog.jonathangcohen.com/tagged/'+blogTumblrCategory+'">'+blogTumblrCategory+'</a>'; //print date var k = x[i].getElementsByTagName("pubDate")[0].childNodes[0].nodeValue thisDate = new Date(); thisDate = formatTumblrDate(k); document.getElementById("getBlogPublishDate1").innerHTML = thisDate; //print title var blogTumblrTitle = x[i].getElementsByTagName("title")[0].childNodes[0].nodeValue var blogTumblrLink = x[i].getElementsByTagName("link")[0].childNodes[0].nodeValue document.getElementById("getBlogTitle1").innerHTML = '<a class="BlogTitleLinkStyle" href="'+blogTumblrLink+'">'+blogTumblrTitle+'</a>'; } if (i == 1){ //print category var blogTumblrCategory = x[i].getElementsByTagName("category")[0].childNodes[0].nodeValue document.getElementById("getBlogCategory2").innerHTML = '<a class="BlogTitleLinkStyle" href="http://blog.jonathangcohen.com/tagged/'+blogTumblrCategory+'">'+blogTumblrCategory+'</a>'; //print date var k = x[i].getElementsByTagName("pubDate")[0].childNodes[0].nodeValue thisDate = new Date(); thisDate = formatTumblrDate(k); document.getElementById("getBlogPublishDate2").innerHTML = thisDate; //print title var blogTumblrTitle = x[i].getElementsByTagName("title")[0].childNodes[0].nodeValue var blogTumblrLink = x[i].getElementsByTagName("link")[0].childNodes[0].nodeValue document.getElementById("getBlogTitle2").innerHTML = '<a class="BlogTitleLinkStyle" href="'+blogTumblrLink+'">'+blogTumblrTitle+'</a>'; } if (i == 2){ //print category var blogTumblrCategory = x[i].getElementsByTagName("category")[0].childNodes[0].nodeValue document.getElementById("getBlogCategory3").innerHTML = '<a class="BlogTitleLinkStyle" href="http://blog.jonathangcohen.com/tagged/'+blogTumblrCategory+'">'+blogTumblrCategory+'</a>'; //print date var k = x[i].getElementsByTagName("pubDate")[0].childNodes[0].nodeValue thisDate = new Date(); thisDate = formatTumblrDate(k); document.getElementById("getBlogPublishDate3").innerHTML = thisDate; //print title var blogTumblrTitle = x[i].getElementsByTagName("title")[0].childNodes[0].nodeValue var blogTumblrLink = x[i].getElementsByTagName("link")[0].childNodes[0].nodeValue document.getElementById("getBlogTitle3").innerHTML = '<a class="BlogTitleLinkStyle" href="'+blogTumblrLink+'">'+blogTumblrTitle+'</a>'; } } } function formatTumblrDate(k){ d = new Date(k); var curr_date = d.getDate(); var curr_month = d.getMonth(); curr_month++; var curr_year = d.getFullYear(); printDate = (curr_month + "/" + curr_date + "/" + curr_year); return printDate; } Thank you!

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• Efficient representation of Hierarchies in Hibernate.

  - by Alison G

  I'm having some trouble representing an object hierarchy in Hibernate. I've searched around, and haven't managed to find any examples doing this or similar - you have my apologies if this is a common question. I have two types which I'd like to persist using Hibernate: Groups and Items. * Groups are identified uniquely by a combination of their name and their parent. * The groups are arranged in a number of trees, such that every Group has zero or one parent Group. * Each Item can be a member of zero or more Groups. Ideally, I'd like a bi-directional relationship allowing me to get: * all Groups that an Item is a member of * all Items that are a member of a particular Group or its descendants. I also need to be able to traverse the Group tree from the top in order to display it on the UI. The basic object structure would ideally look like this: class Group { ... /** @return all items in this group and its descendants */ Set<Item> getAllItems() { ... } /** @return all direct children of this group */ Set<Group> getChildren() { ... } ... } class Item { ... /** @return all groups that this Item is a direct member of */ Set<Group> getGroups() { ... } ... } Originally, I had just made a simple bi-directional many-to-many relationship between Items and Groups, such that fetching all items in a group hierarchy required recursion down the tree, and fetching groups for an Item was a simple getter, i.e.: class Group { ... private Set<Item> items; private Set<Group> children; ... /** @return all items in this group and its descendants */ Set<Item> getAllItems() { Set<Item> allItems = new HashSet<Item>(); allItems.addAll(this.items); for(Group child : this.getChildren()) { allItems.addAll(child.getAllItems()); } return allItems; } /** @return all direct children of this group */ Set<Group> getChildren() { return this.children; } ... } class Item { ... private Set<Group> groups; /** @return all groups that this Item is a direct member of */ Set<Group> getGroups() { return this.groups; } ... } However, this resulted in multiple database requests to fetch the Items in a Group with many descendants, or for retrieving the entire Group tree to display in the UI. This seems very inefficient, especially with deeper, larger group trees. Is there a better or standard way of representing this relationship in Hibernate? Am I doing anything obviously wrong or stupid? My only other thought so far was this: Replace the group's id, parent and name fields with a unique "path" String which specifies the whole ancestry of a group, e.g.: /rootGroup /rootGroup/aChild /rootGroup/aChild/aGrandChild The join table between Groups and Items would then contain group_path and item_id. This immediately solves the two issues I was suffering previously: 1. The entire group hierarchy can be fetched from the database in a single query and reconstructed in-memory. 2. To retrieve all Items in a group or its descendants, we can select from group_item where group_path='N' or group_path like 'N/%' However, this seems to defeat the point of using Hibernate. All thoughts welcome!

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• Entity Framework Generic Repository Error

  - by Jeff Ancel

  I am trying to create a very generic generics repository for my Entity Framework repository that has the basic CRUD statements and uses an Interface. I have hit a brick wall head first and been knocked over. Here is my code, written in a console application, using a Entity Framework Model, with a table named Hurl. Simply trying to pull back the object by its ID. Here is the full application code. using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Data.Objects; using System.Linq.Expressions; using System.Reflection; using System.Data.Objects.DataClasses; namespace GenericsPlay { class Program { static void Main(string[] args) { var hs = new HurlRepository(new hurladminEntity()); var hurl = hs.Load<Hurl>(h => h.Id == 1); Console.Write(hurl.ShortUrl); Console.ReadLine(); } } public interface IHurlRepository { T Load<T>(Expression<Func<T, bool>> expression); } public class HurlRepository : IHurlRepository, IDisposable { private ObjectContext _objectContext; public HurlRepository(ObjectContext objectContext) { _objectContext = objectContext; } public ObjectContext ObjectContext { get { return _objectContext; } } private Type GetBaseType(Type type) { Type baseType = type.BaseType; if (baseType != null && baseType != typeof(EntityObject)) { return GetBaseType(type.BaseType); } return type; } private bool HasBaseType(Type type, out Type baseType) { Type originalType = type.GetType(); baseType = GetBaseType(type); return baseType != originalType; } public IQueryable<T> GetQuery<T>() { Type baseType; if (HasBaseType(typeof(T), out baseType)) { return this.ObjectContext.CreateQuery<T>("[" + baseType.Name.ToString() + "]").OfType<T>(); } else { return this.ObjectContext.CreateQuery<T>("[" + typeof(T).Name.ToString() + "]"); } } public T Load<T>(Expression<Func<T, bool>> whereCondition) { return this.GetQuery<T>().Where(whereCondition).First(); } public void Dispose() { if (_objectContext != null) { _objectContext.Dispose(); } } } } Here is the error that I am getting: System.Data.EntitySqlException was unhandled Message="'Hurl' could not be resolved in the current scope or context. Make sure that all referenced variables are in scope, that required schemas are loaded, and that namespaces are referenced correctly., near escaped identifier, line 3, column 1." Source="System.Data.Entity" Column=1 ErrorContext="escaped identifier" ErrorDescription="'Hurl' could not be resolved in the current scope or context. Make sure that all referenced variables are in scope, that required schemas are loaded, and that namespaces are referenced correctly." This is where I am attempting to extract this information from. http://blog.keithpatton.com/2008/05/29/Polymorphic+Repository+For+ADONet+Entity+Framework.aspx

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• Organising XML results as cells in container (AS3)

  - by PJ Palomaki

  Hi, I'm having some problems figuring out how to organise data pulled off XML in cells within a container. I'm sure this should be a basic thing in AS3, but my head's fried.. can anyone help? Basically an array if fed to callThumbs() which iterates through it and compares the entries with preloaded XML _my_images. If match is found, it's sent to processXML which loads all relevant info and loads a .jpg thumbnail. All this is then fed to createCell which creates a specific cell with position values depending on x_counter and y_counter values (4 cells in a row) and adds the cell into a container _container_mc. The Problem: This all works fine and looks fine, the problem is that the cells within the container do not display in descending order. They are in random order, probably because some of the .jpg's takes longer to load etc. How do I easily organise the cells within the container in descending order by the XML .id value? Or how do I tell Flash to wait till the thumbnail and data is loaded and the cell created and added? Thanks guys, would really appreciate all the help! PJ //Flash (AS3) function callThumbs(_my_results:Array):void { // selector = 1 for specific items, 2 for search items var _thumb_url:XML; for (var r:Number=0; r < _my_results.length; r++) { // iterate through results vector, compare with _my_images XML .id for (var i:Number=0; i < _my_images.length(); i++) { if (_my_images[i][email protected]() == _my_results[r]) { _thumb_url=_my_images[i]; processXML(_thumb_url, i); } } } } // End callThumbs function processXML(imageXML:XML, num:Number) { // Processes XML data and loads .jpg thumbnail var _thumb_loader=new Loader(); _thumb_loader.load(new URLRequest("thumbs/thumb_sm/" + imageXML.@id + "_st.jpg")); _thumb_loader.contentLoaderInfo.addEventListener(Event.COMPLETE,thumbLoaded); _thumb_loader.contentLoaderInfo.addEventListener(IOErrorEvent.IO_ERROR, urlNotFound); var id:XMLList = new XMLList; id = imageXML.@id; var description:XMLList = new XMLList; description = imageXML.@description; function urlNotFound(event:IOErrorEvent):void { trace("The image URL '" + String(imageXML.@id) + "' was not found."); } function thumbLoaded(e:Event):void { var imageLoader:Loader = Loader(e.target.loader); var bm:Bitmap = Bitmap(imageLoader.content); createCell(bm, id, description, num); adjustFooterBar(); // Adjust bottom footer } } // End processXML private function createCell(_image:Bitmap, _id, _description:String, _position):void { // Creates a cell with data, add to container var _cell_mc = new CellTitle(); _cell_mc.initCell(_image, _id, _description, _position, x_counter, y_counter); if (x_counter+1 < 4) { x_counter++; } else { x_counter = 0; y_counter++; } _container_mc.addChild(_cell_mc); // movieclip container } // End createCell

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• Proxy Issues with Javascript Cross Domain RSS Feed Parsing

  - by Amir

  This is my Javascript function which grabs an rss feed via the proxy script and then spits out the 5 latest rss items from the feed along with a link to my stylesheet: function getWidget (feed,limit) { if (window.XMLHttpRequest) { xhttp=new XMLHttpRequest() } else { xhttp=new ActiveXObject("Microsoft.XMLHTTP") } xhttp.open("GET","http://MYSITE/proxy.php?url="+feed,false); xhttp.send(""); xmlDoc=xhttp.responseXML; var x = 1; var div = document.getElementById("div"); srdiv.innerHTML = '<link type="text/css" href="http://MYSITE/css/widget.css" rel="stylesheet" /><div id="rss-title"></div></h3><div id="items"></div><br /><br /><a href="http://MYSITE">Powered by MYSITE</a>'; document.body.appendChild(div); content=xmlDoc.getElementsByTagName("title"); thelink=xmlDoc.getElementsByTagName("link"); document.getElementByTagName("rss-title").innerHTML += content[0].childNodes[0].nodeValue; for (x=1;x<=limit;srx++) { y=x; y--; var shout = '<div class="item"><a href="'+thelink[y].childNodes[0].nodeValue+'">'+content[x].childNodes[0].nodeValue+'</a></div>'; document.getElementById("items").innerHTML += shout; } } Here is the the code from proxy.php: $session = curl_init($_GET['url']); // Open the Curl session curl_setopt($session, CURLOPT_HEADER, false); // Don't return HTTP headers curl_setopt($session, CURLOPT_RETURNTRANSFER, true); // Do return the contents of the call $xml = curl_exec($session); // Make the call header("Content-Type: text/xml"); // Set the content type appropriately echo $xml; // Spit out the xml curl_close($session); // And close the session Now when I try to load this on any domain that's not my site nothing loads. I get no JS errors, but I in the Console tab in firebug I get "407 Proxy Authentication Required" So I'm not really sure how to make this work. The goal is to be able to grab the RSS feed, parse it to grab the titles and links and spit it out into some HTML on any website on the web. I"m basically making a simple RSS widget for my site's various RSS feeds. My Javascript is wack Also, I'm really a beginner with Javascript. I know jQuery pretty well, but I wasn't able to use it in this case, because this script will be embeded on any site and I can't really rely on the jQuery library. So I was decided to write some basic Javascript relying on the default XML parsing options available. Any suggestions here would be cool. Thanks! What's with the x and y They way my site creates RSS feeds is that the first title is actually the RSS feed title. The second title is the title of the first item. The first link is the link to the first item. So when using the javascript to get the title, I had to first grab the first title (which is the RSS title) and then start with the second title that being the first title of the item. Sorry for the confusion, but I don't think this is related to my issue. Just wanted to clarify my code.

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• this program runs but not correctly:brief decription of what i am trying to do can someone tell me i

  - by user320950

  this is what i have to do: write a program that determines the grade dispersal for 100 students You are to read the exam scores into three arrays, one array for each exam. You must then calculate how many students scored A’s (90 or above), B’s (80 or above), C’s (70 or above), D’s (60 or above), and F’s (less than 60). Do this for each exam and write the distribution to the screen. // basic file operations #include <iostream> #include <fstream> using namespace std; int read_file_in_array(double exam[100][3]); double calculate_total(double exam1[], double exam2[], double exam3[]); // function that calcualates grades to see how many 90,80,70,60 //void display_totals(); double exam[100][3]; int main() { double go,go2,go3; double exam[100][3],exam1[100],exam2[100],exam3[100]; go=read_file_in_array(exam); go2=calculate_total(exam1,exam2,exam3); //go3=display_totals(); cout << go,go2,go3; return 0; } /* int display_totals() { int grade_total; grade_total=calculate_total(exam1,exam2,exam3); return 0; } */ double calculate_total(double exam1[],double exam2[],double exam3[]) { int calc_tot,above90=0, above80=0, above70=0, above60=0,i,j, fail=0; double exam[100][3]; calc_tot=read_file_in_array(exam); for(i=0;i<100;i++) { for (j=0; j<3; j++) { exam1[i]=exam[100][0]; exam2[i]=exam[100][1]; exam3[i]=exam[100][2]; if(exam[i][j] <=90 && exam[i][j] >=100) { above90++; { if(exam[i][j] <=80 && exam[i][j] >=89) { above80++; { if(exam[i][j] <=70 && exam[i][j] >=79) { above70++; { if(exam[i][j] <=60 && exam[i][j] >=69) { above60++; { if(exam[i][j] >=59) { fail++; } } } } } } } } } } } return 0; } int read_file_in_array(double exam[100][3]) { ifstream infile; int exam1[100]; int exam2[100]; int exam3[100]; infile.open("grades.txt");// file containing numbers in 3 columns if(infile.fail()) // checks to see if file opended { cout << "error" << endl; } int num, i=0,j=0; while(!infile.eof()) // reads file to end of line { for(i=0;i<100;i++) // array numbers less than 100 { for(j=0;j<3;j++) // while reading get 1st array or element infile >> exam[i][j]; infile >> exam[i][j]; infile >> exam[i][j]; cout << exam[i][j] << endl; { if (! (infile >> exam[i][j]) ) cout << exam[i][j] << endl; } exam[i][j]=exam1[i]; exam[i][j]=exam2[i]; exam[i][j]=exam3[i]; } infile.close(); } return 0; }

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• Languages and VMs: Features that are hard to optimize and why

  - by mrjoltcola

  I'm doing a survey of features in preparation for a research project. Name a mainstream language or language feature that is hard to optimize, and why the feature is or isn't worth the price paid, or instead, just debunk my theories below with anecdotal evidence. Before anyone flags this as subjective, I am asking for specific examples of languages or features, and ideas for optimization of these features, or important features that I haven't considered. Also, any references to implementations that prove my theories right or wrong. Top on my list of hard to optimize features and my theories (some of my theories are untested and are based on thought experiments): 1) Runtime method overloading (aka multi-method dispatch or signature based dispatch). Is it hard to optimize when combined with features that allow runtime recompilation or method addition. Or is it just hard, anyway? Call site caching is a common optimization for many runtime systems, but multi-methods add additional complexity as well as making it less practical to inline methods. 2) Type morphing / variants (aka value based typing as opposed to variable based) Traditional optimizations simply cannot be applied when you don't know if the type of someting can change in a basic block. Combined with multi-methods, inlining must be done carefully if at all, and probably only for a given threshold of size of the callee. ie. it is easy to consider inlining simple property fetches (getters / setters) but inlining complex methods may result in code bloat. The other issue is I cannot just assign a variant to a register and JIT it to the native instructions because I have to carry around the type info, or every variable needs 2 registers instead of 1. On IA-32 this is inconvenient, even if improved with x64's extra registers. This is probably my favorite feature of dynamic languages, as it simplifies so many things from the programmer's perspective. 3) First class continuations - There are multiple ways to implement them, and I have done so in both of the most common approaches, one being stack copying and the other as implementing the runtime to use continuation passing style, cactus stacks, copy-on-write stack frames, and garbage collection. First class continuations have resource management issues, ie. we must save everything, in case the continuation is resumed, and I'm not aware if any languages support leaving a continuation with "intent" (ie. "I am not coming back here, so you may discard this copy of the world"). Having programmed in the threading model and the contination model, I know both can accomplish the same thing, but continuations' elegance imposes considerable complexity on the runtime and also may affect cache efficienty (locality of stack changes more with use of continuations and co-routines). The other issue is they just don't map to hardware. Optimizing continuations is optimizing for the less-common case, and as we know, the common case should be fast, and the less-common cases should be correct. 4) Pointer arithmetic and ability to mask pointers (storing in integers, etc.) Had to throw this in, but I could actually live without this quite easily. My feelings are that many of the high-level features, particularly in dynamic languages just don't map to hardware. Microprocessor implementations have billions of dollars of research behind the optimizations on the chip, yet the choice of language feature(s) may marginalize many of these features (features like caching, aliasing top of stack to register, instruction parallelism, return address buffers, loop buffers and branch prediction). Macro-applications of micro-features don't necessarily pan out like some developers like to think, and implementing many languages in a VM ends up mapping native ops into function calls (ie. the more dynamic a language is the more we must lookup/cache at runtime, nothing can be assumed, so our instruction mix is made up of a higher percentage of non-local branching than traditional, statically compiled code) and the only thing we can really JIT well is expression evaluation of non-dynamic types and operations on constant or immediate types. It is my gut feeling that bytecode virtual machines and JIT cores are perhaps not always justified for certain languages because of this. I welcome your answers.

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