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  • java-eclipse-jsf -404 error

    - by ognistysztorm
    I am trying to create my first project in JSF (Eclipse Juno). I have only one jsp file witch contain: <?xml version="1.0" encoding="ISO-8859-1" ?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xmlns:f="http://java.sun.com/jsf/core" xmlns:h="http://java.sun.com/jsf/html" xmlns:ui="http://java.sun.com/jsf/facelets"> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" /> <title>Insert title here</title> </head> <body> <f:view> <ui:component>Hello World</ui:component> </f:view> </body> </html> ...but when I try run it on server I receiving 404 error. I add jsf.jar and jstl.jar to my bulid path. this is web.xml: <?xml version="1.0" encoding="UTF-8"?> <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0"> <display-name>inwert</display-name> <servlet> <servlet-name>Faces Servlet</servlet-name> <servlet-class>javax.faces.webapp.FacesServlet</servlet-class> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>Faces Servlet</servlet-name> <url-pattern>/faces/*</url-pattern> </servlet-mapping> <context-param> <description>State saving method: 'client' or 'server' (=default). See JSF Specification 2.5.2</description> <param-name>javax.faces.STATE_SAVING_METHOD</param-name> <param-value>client</param-value> </context-param> <context-param> <param-name>javax.servlet.jsp.jstl.fmt.localizationContext</param-name> <param-value>resources.application</param-value> </context-param> <listener> <listener-class>com.sun.faces.config.ConfigureListener</listener-class> </listener> </web-app> After 3 Hours I give up :( Could anyone help me?

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  • What is "elegant" code?

    - by Breton
    I see a lot of lip service and talk about the most "elegant" way to do this or that. I think if you spend enough time programming you begin to obtain a sort of intuitive feel for what it is we call "elegance". But I'm curious. Even if we can look at a bit of code, and say instinctively "That's elegant", or "That's messy", I wonder if any of us really understands what that means. Is there a precise definition for this "elegance" we keep referring to? If there is, what is it? Now, what I mean by a precise definition, is a series of statements which can be used to derive questions about a peice of code, or a program as a whole, and determine objectively, or as objectively as possible, whether that code is "elegant" or not. May I assert, that perhaps no such definition exists, and it's all just personal preference. In this case, I ask you a slightly different question: Is there a better word for "elegance", or a better set of attributes to use for judging code quality that is perhaps more objective than merely appealing to individual intuition and taste? Perhaps code quality is a matter of taste, and the answer to both of my questions is "no". But I can't help but feel that we could be doing better than just expressing wishy washy feelings about our code quality. For example, user interface design is something that to a broad range of people looks for all the world like a field of study that oughtta be 100% subjective matter of taste. But this is shockingly and brutally not the case, and there are in fact many objective measures that can be applied to a user interface to determine its quality. A series of tests could be written to give a definitive and repeatable score to user interface quality. (See GOMS, for instance). Now, okay. is Elegance simply "code quality" or is it something more? Is it something that can be measured? Or is it a matter of taste? Does our profession have room for taste? Maybe I'm asking the wrong questions altogether. Help me out here. Bonus Round If there is such a thing as elegance in code, and that concept is useful, do you think that justifies classifying the field of programming as an "Art" capital A, or merely a "craft". Or is it just an engineering field populated by a bunch of wishful thinking humans? Consider this question in the light of your thoughts about the elegance question. Please note that there is a distinction between code which is considered "art" in itself, and code that was written merely in the service of creating an artful program. When I ask this question, I ask if the code itself justifies calling programming an art. Bounty Note I liked the answers to this question so much, I think I'd like to make a photographic essay book from it. Released as a free PDF, and published on some kind of on demand printing service of course, such as "zazz" or "tiggle" or "printley" or something . I'd like some more answers, please!

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  • Post calls RedirectToAction but view specified in RedirectToAction is not rendered

    - by W4IK
    Here's some of the html <form id="frmSubmit" action="/Viewer" style="display:none;"> <div id="renderSubmit" class="renderReport"> <input type="hidden" name="reportYear" id="reportYear" value="" /> <input type="hidden" name="reportMonth" id="reportMonth" value="" /> <input type="hidden" name="propIds" id="propIds" value="" /> <input type="hidden" name="reportName" id="reportName" value="" /> <input type="hidden" name="reportYearFrom" id="reportYearFrom" value="" /> <input type="hidden" name="reportMonthFrom" id="reportMonthFrom" value="" /> <input type="hidden" name="reportYearTo" id="reportYearTo" value="" /> <input type="hidden" name="reportMonthTo" id="reportMonthTo" value="" /> </div> </form> a little further down the page <div id="reportList" class="renderReport"> <fieldset style="width:105%;"> <legend class="reportStepLegend">Step 3. <br /> Click a report name below to view a report</legend> <br /> <% foreach (ReportMetaData item in (ReportMetaDataContainer)ViewData.Model) { %> <div> <input id=<%=item.SSRSName%> type="button" class="reportLink" value="<%=item.DisplayName%>" /> </div> <%}%> </fieldset> </div> Here's the javascript that gets called when the button is clicked $('.reportLink').click(function() { if (CheckDateAndProps() === true) { $('#reportName').val(this.id); var formData = $("#frmSubmit").serializeArray(); $.post('Home/PostViewer/', formData); } }); Note...i did have the $.post like so earlier...but it didn't seem to make any difference $.post('Home/PostViewer/', formData, function(data) { alert(data.Result); }, "json"); Here's the controller code [AcceptVerbs(HttpVerbs.Post)] public ActionResult PostViewer(string reportYear, string reportMonth, string propIds, string reportName, string reportYearFrom, string reportMonthFrom, string reportYearTo, string reportMonthTo) { return RedirectToAction("Viewer"); } All is good in the world up to this point..I'm hitting the above method and all the values are populated. Here's the get ActionResult method [AcceptVerbs(HttpVerbs.Get)] public ActionResult Viewer(string reportYear, string reportMonth, string propIds, string reportName, string reportYearFrom, string reportMonthFrom, string reportYearTo, string reportMonthTo) { return View(); } I'm hitting this too...not seeing any values in the parameters...but that's just because I haven't passed them in yet...I don't think that's whats keeping the Viewer page from displaying.? Now...one would one expect the Viewer view to be rendered...right?...well all I see is the page that this was called from...it never displays the Viewer page???!!?!? Here's the routes from global.asax routes.MapRoute( "Viewer", // Route name "Home/Viewer", // URL with parameters new { controller = "Home", action = "Viewer" } // Parameter defaults ); routes.MapRoute( "Default", // Route name "{controller}/{action}/{id}", // URL with parameters new { controller = "Home", action = "Index", id = "" } // Parameter defaults ); I can browse directly to the page http://localhost:50083/Home/Viewer and when I do so I hit the get ActionResult method and the page renders just fine. Any help is greatly appreciated!

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  • How to add the coding for displaying the address when a particular set of latitude and longitude is

    - by KKC
    import com.google.android.maps.GeoPoint; import com.google.android.maps.MapActivity; import com.google.android.maps.MapController; import com.google.android.maps.MapView; import android.os.Bundle; import android.view.KeyEvent; import android.view.View; import android.widget.AdapterView; import android.widget.ArrayAdapter; import android.widget.Spinner; import android.widget.AdapterView.OnItemSelectedListener; public class PopularAttractions extends MapActivity { private String[ ][ ] locations = { {"Singapore Zoological Garden","1.40502,103.793449"}, {"Singapore Night Safari","1.4037,103.789467"}, {"Jurong BirdPark","1.32005,103.707153"}, {"Jurong Reptile Park","1.321177,103.708486"}, {"Singapore Botanic Garden","1.31471,103.815689"}, {"Sungei Buloh Wetland Reserver","1.445144,103.729595"}, {"Escape Theme Park","1.38104,103.936928"}, {"Snow City","1.32823,103.74263"}, {"Super Ice World","1.300422,103.875348"}, {"Chinatown Heritage Center","1.2836,103.84425"}, {"Singapore Science Center","1.3249,103.740578"}, {"Red Dot Design Museum","1.277762,103.846225"}, {"G-Max Reverse Bungy","1.2906,103.845322"}, {"NEWater Visitor Center","1.33105,103.955311"} }; private Spinner spinnerView; private MapView mapView; private MapController mc; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); spinnerView = (Spinner) this.findViewById(R.id.spinner1); mapView = (MapView) findViewById(R.id.mapview1); mc = mapView.getController(); ArrayAdapter<CharSequence> adapter = new ArrayAdapter<CharSequence>(this, android.R.layout.simple_spinner_dropdown_item); //--add the various locations--- for(int i = 0; i < locations.length; i++) adapter.add(locations[i][0]); adapter.setDropDownViewResource( android.R.layout.simple_spinner_dropdown_item); spinnerView.setAdapter(adapter); spinnerView.setOnItemSelectedListener(selectListener); gotoSelected(); } //---when user selects an item--- private OnItemSelectedListener selectListener = new OnItemSelectedListener() { //---these are two methods you need to implement--- public void onItemSelected( AdapterView<?>parent, View v, int position, long id) { gotoSelected(); } public void onNothingSelected(AdapterView<?> arg0) {} }; //---when an item has been selected--- public void gotoSelected() { int index = spinnerView.getSelectedItemPosition(); String[] coordinates = locations[index][1].split(","); double lat = Double.parseDouble(coordinates[0]); double lng = Double.parseDouble(coordinates[1]); GeoPoint location = new GeoPoint ( (int)(lat * 1E6), (int)(lng * 1E6)); mc.animateTo(location); mc.setZoom(16); if (mapView.isSatellite()) mapView.setSatellite(false); else mapView.setStreetView(true); mapView.invalidate(); } public boolean onKeyDown(int keyCode, KeyEvent event) { MapController mc = mapView.getController(); switch (keyCode) { case KeyEvent.KEYCODE_3: mc.zoomIn(); break; case KeyEvent.KEYCODE_1: mc.zoomOut(); break; } return super.onKeyDown(keyCode, event); } @Override protected boolean isRouteDisplayed(){ //TODO Auto-generated method sub return false; } }

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  • Is it possible to implement bitwise operators using integer arithmetic?

    - by Statement
    Hello World! I am facing a rather peculiar problem. I am working on a compiler for an architecture that doesn't support bitwise operations. However, it handles signed 16 bit integer arithmetics and I was wondering if it would be possible to implement bitwise operations using only: Addition (c = a + b) Subtraction (c = a - b) Division (c = a / b) Multiplication (c = a * b) Modulus (c = a % b) Minimum (c = min(a, b)) Maximum (c = max(a, b)) Comparisons (c = (a < b), c = (a == b), c = (a <= b), et.c.) Jumps (goto, for, et.c.) The bitwise operations I want to be able to support are: Or (c = a | b) And (c = a & b) Xor (c = a ^ b) Left Shift (c = a << b) Right Shift (c = a b) (All integers are signed so this is a problem) Signed Shift (c = a b) One's Complement (a = ~b) (Already found a solution, see below) Normally the problem is the other way around; how to achieve arithmetic optimizations using bitwise hacks. However not in this case. Writable memory is very scarce on this architecture, hence the need for bitwise operations. The bitwise functions themselves should not use a lot of temporary variables. However, constant read-only data & instruction memory is abundant. A side note here also is that jumps and branches are not expensive and all data is readily cached. Jumps cost half the cycles as arithmetic (including load/store) instructions do. On other words, all of the above supported functions cost twice the cycles of a single jump. Some thoughts that might help: I figured out that you can do one's complement (negate bits) with the following code: // Bitwise one's complement b = ~a; // Arithmetic one's complement b = -1 - a; I also remember the old shift hack when dividing with a power of two so the bitwise shift can be expressed as: // Bitwise left shift b = a << 4; // Arithmetic left shift b = a * 16; // 2^4 = 16 // Signed right shift b = a >>> 4; // Arithmetic right shift b = a / 16; For the rest of the bitwise operations I am slightly clueless. I wish the architects of this architecture would have supplied bit-operations. I would also like to know if there is a fast/easy way of computing the power of two (for shift operations) without using a memory data table. A naive solution would be to jump into a field of multiplications: b = 1; switch (a) { case 15: b = b * 2; case 14: b = b * 2; // ... exploting fallthrough (instruction memory is magnitudes larger) case 2: b = b * 2; case 1: b = b * 2; } Or a Set & Jump approach: switch (a) { case 15: b = 32768; break; case 14: b = 16384; break; // ... exploiting the fact that a jump is faster than one additional mul // at the cost of doubling the instruction memory footprint. case 2: b = 4; break; case 1: b = 2; break; }

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  • Rx IObservable buffering to smooth out bursts of events

    - by Dan
    I have an Observable sequence that produces events in rapid bursts (ie: five events one right after another, then a long delay, then another quick burst of events, etc.). I want to smooth out these bursts by inserting a short delay between events. Imagine the following diagram as an example: Raw: --oooo--------------ooooo-----oo----------------ooo| Buffered: --o--o--o--o--------o--o--o--o--o--o--o---------o--o--o| My current approach is to generate a metronome-like timer via Observable.Interval() that signals when it's ok to pull another event from the raw stream. The problem is that I can't figure out how to then combine that timer with my raw unbuffered observable sequence. IObservable.Zip() is close to doing what I want, but it only works so long as the raw stream is producing events faster than the timer. As soon as there is a significant lull in the raw stream, the timer builds up a series of unwanted events that then immediately pair up with the next burst of events from the raw stream. Ideally, I want an IObservable extension method with the following function signature that produces the bevaior I've outlined above. Now, come to my rescue StackOverflow :) public static IObservable<T> Buffered(this IObservable<T> src, TimeSpan minDelay) PS. I'm brand new to Rx, so my apologies if this is a trivially simple question... 1. Simple yet flawed approach Here's my initial naive and simplistic solution that has quite a few problems: public static IObservable<T> Buffered<T>(this IObservable<T> source, TimeSpan minDelay) { Queue<T> q = new Queue<T>(); source.Subscribe(x => q.Enqueue(x)); return Observable.Interval(minDelay).Where(_ => q.Count > 0).Select(_ => q.Dequeue()); } The first obvious problem with this is that the IDisposable returned by the inner subscription to the raw source is lost and therefore the subscription can't be terminated. Calling Dispose on the IDisposable returned by this method kills the timer, but not the underlying raw event feed that is now needlessly filling the queue with nobody left to pull events from the queue. The second problem is that there's no way for exceptions or end-of-stream notifications to be propogated through from the raw event stream to the buffered stream - they are simply ignored when subscribing to the raw source. And last but not least, now I've got code that wakes up periodically regardless of whether there is actually any work to do, which I'd prefer to avoid in this wonderful new reactive world. 2. Way overly complex appoach To solve the problems encountered in my initial simplistic approach, I wrote a much more complicated function that behaves much like IObservable.Delay() (I used .NET Reflector to read that code and used it as the basis of my function). Unfortunately, a lot of the boilerplate logic such as AnonymousObservable is not publicly accessible outside the system.reactive code, so I had to copy and paste a lot of code. This solution appears to work, but given its complexity, I'm less confident that its bug free. I just can't believe that there isn't a way to accomplish this using some combination of the standard Reactive extensions. I hate feeling like I'm needlessly reinventing the wheel, and the pattern I'm trying to build seems like a fairly standard one.

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  • Jasper report always showing no content, why?

    - by spderosso
    Hi, I have the following code: InputStream reportFile = MyPage.this.getClass().getResourceAsStream("test.jrxml"); HashMap<String, String> parameters = new HashMap<String, String>(); parameters.put("StringParameterName", "show me"); try { JasperReport report = JasperCompileManager.compileReport(reportFile); JasperPrint print = JasperFillManager.fillReport(report, parameters); return JasperExportManager.exportReportToPdf(print); } catch (JRException e) { // TODO Auto-generated catch block e.printStackTrace(); return null; } And the test.jrxml looks like this (I generated part of it with the iReport, the only thing I did was to remove the language="groovy" attribute): <?xml version="1.0" encoding="UTF-8"?> <jasperReport xmlns="http://jasperreports.sourceforge.net/jasperreports" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://jasperreports.sourceforge.net/jasperreports http://jasperreports.sourceforge.net/xsd/jasperreport.xsd" name="test" pageWidth="595" pageHeight="842" columnWidth="555" leftMargin="20" rightMargin="20" topMargin="20" bottomMargin="20"> <property name="ireport.zoom" value="1.0"/> <property name="ireport.x" value="0"/> <property name="ireport.y" value="0"/> <parameter name="StringParameterName" isForPrompting="false" class="java.lang.String"/> <background> <band splitType="Stretch"/> </background> <title> <band height="20"> <staticText> <reportElement x="180" y="0" width="200" height="20"/> <text><![CDATA[Hello World!]]></text> </staticText> </band> </title> <pageHeader> <band height="35" splitType="Stretch"/> </pageHeader> <columnHeader> <band height="61" splitType="Stretch"/> </columnHeader> <detail> <band height="125" splitType="Stretch"> <textField> <reportElement x="243" y="77" width="100" height="20"/> <textElement/> <textFieldExpression class="java.lang.String"><![CDATA[$P{StringParameterName}]]></textFieldExpression> </textField> </band> </detail> <columnFooter> <band height="45" splitType="Stretch"/> </columnFooter> <pageFooter> <band height="54" splitType="Stretch"/> </pageFooter> <summary> <band height="42" splitType="Stretch"/> </summary> </jasperReport> As a result I always get a blank pdf file. What could be the reason?

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  • Error data: line 2 column 1 when using pycurl with gzip stream

    - by Sagar Hatekar
    Thanks for reading. Background: I am trying to read a streaming API feed that returns data in JSON format, and then storing this data to a pymongo collection. The streaming API requires a "Accept-Encoding" : "Gzip" header. What's happening: Code fails on json.loads and outputs - Extra data: line 2 column 1 - line 4 column 1 (char 1891 - 5597) (Refer Error Log below) This does NOT happen while parsing every JSON object - it happens at random. My guess is I am encountering some weird JSON object after every "x" proper JSON objects. I did reference how to use pycurl if requested data is sometimes gzipped, sometimes not? and Encoding error while deserializing a json object from Google but so far have been unsuccessful at resolving this error. Could someone please help me out here? Error Log: Note: The raw dump of the JSON object below is basically using the repr() method. '{"id":"tag:search.twitter.com,2005:207958320747782146","objectType":"activity","actor":{"objectType":"person","id":"id:twitter.com:493653150","link":"http://www.twitter.com/Deathnews_7_24","displayName":"Death News 7/24","postedTime":"2012-02-16T01:30:12.000Z","image":"http://a0.twimg.com/profile_images/1834408513/deathnewstwittersquare_normal.jpg","summary":"Crashes, Murders, Suicides, Accidents, Crime and Naturals Death News From All Around World","links":[{"href":"http://www.facebook.com/DeathNews724","rel":"me"}],"friendsCount":56,"followersCount":14,"listedCount":1,"statusesCount":1029,"twitterTimeZone":null,"utcOffset":null,"preferredUsername":"Deathnews_7_24","languages":["tr"]},"verb":"post","postedTime":"2012-05-30T22:15:02.000Z","generator":{"displayName":"web","link":"http://twitter.com"},"provider":{"objectType":"service","displayName":"Twitter","link":"http://www.twitter.com"},"link":"http://twitter.com/Deathnews_7_24/statuses/207958320747782146","body":"Kathi Kamen Goldmark, Writers\xe2\x80\x99 Catalyst, Dies at 63 http://t.co/WBsNlNtA","object":{"objectType":"note","id":"object:search.twitter.com,2005:207958320747782146","summary":"Kathi Kamen Goldmark, Writers\xe2\x80\x99 Catalyst, Dies at 63 http://t.co/WBsNlNtA","link":"http://twitter.com/Deathnews_7_24/statuses/207958320747782146","postedTime":"2012-05-30T22:15:02.000Z"},"twitter_entities":{"urls":[{"display_url":"nytimes.com/2012/05/30/boo\xe2\x80\xa6","indices":[52,72],"expanded_url":"http://www.nytimes.com/2012/05/30/books/kathi-kamen-goldmark-writers-catalyst-dies-at-63.html","url":"http://t.co/WBsNlNtA"}],"hashtags":[],"user_mentions":[]},"gnip":{"language":{"value":"en"},"matching_rules":[{"value":"url_contains: nytimes.com","tag":null}],"klout_score":11,"urls":[{"url":"http://t.co/WBsNlNtA","expanded_url":"http://www.nytimes.com/2012/05/30/books/kathi-kamen-goldmark-writers-catalyst-dies-at-63.html?_r=1"}]}}\r\n{"id":"tag:search.twitter.com,2005:207958321003638785","objectType":"activity","actor":{"objectType":"person","id":"id:twitter.com:178760897","link":"http://www.twitter.com/Mobanu","displayName":"Donald Ochs","postedTime":"2010-08-15T16:33:56.000Z","image":"http://a0.twimg.com/profile_images/1493224811/small_mobany_Logo_normal.jpg","summary":"","links":[{"href":"http://www.mobanuweightloss.com","rel":"me"}],"friendsCount":10272,"followersCount":9698,"listedCount":30,"statusesCount":725,"twitterTimeZone":"Mountain Time (US & Canada)","utcOffset":"-25200","preferredUsername":"Mobanu","languages":["en"],"location":{"objectType":"place","displayName":"Crested Butte, Colorado"}},"verb":"post","postedTime":"2012-05-30T22:15:02.000Z","generator":{"displayName":"twitterfeed","link":"http://twitterfeed.com"},"provider":{"objectType":"service","displayName":"Twitter","link":"http://www.twitter.com"},"link":"http://twitter.com/Mobanu/statuses/207958321003638785","body":"Mobanu: Can Exercise Be Bad for You?: Researchers have found evidence that some people who exercise do worse on ... http://t.co/mTsQlNQO","object":{"objectType":"note","id":"object:search.twitter.com,2005:207958321003638785","summary":"Mobanu: Can Exercise Be Bad for You?: Researchers have found evidence that some people who exercise do worse on ... http://t.co/mTsQlNQO","link":"http://twitter.com/Mobanu/statuses/207958321003638785","postedTime":"2012-05-30T22:15:02.000Z"},"twitter_entities":{"urls":[{"display_url":"nyti.ms/KUmmMa","indices":[116,136],"expanded_url":"http://nyti.ms/KUmmMa","url":"http://t.co/mTsQlNQO"}],"hashtags":[],"user_mentions":[]},"gnip":{"language":{"value":"en"},"matching_rules":[{"value":"url_contains: nytimes.com","tag":null}],"klout_score":12,"urls":[{"url":"http://t.co/mTsQlNQO","expanded_url":"http://well.blogs.nytimes.com/2012/05/30/can-exercise-be-bad-for-you/?utm_medium=twitter&utm_source=twitterfeed"}]}}\r\n' json exception: Extra data: line 2 column 1 - line 4 column 1 (char 1891 - 5597) Header Output: HTTP/1.1 200 OK Content-Type: application/json; charset=UTF-8 Vary: Accept-Encoding Date: Wed, 30 May 2012 22:14:48 UTC Connection: close Transfer-Encoding: chunked Content-Encoding: gzip get_stream.py: #!/usr/bin/env python import sys import pycurl import json import pymongo STREAM_URL = "https://stream.test.com:443/accounts/publishers/twitter/streams/track/Dev.json" AUTH = "userid:passwd" DB_HOST = "127.0.0.1" DB_NAME = "stream_test" class StreamReader: def __init__(self): try: self.count = 0 self.buff = "" self.mongo = pymongo.Connection(DB_HOST) self.db = self.mongo[DB_NAME] self.raw_tweets = self.db["raw_tweets_gnip"] self.conn = pycurl.Curl() self.conn.setopt(pycurl.ENCODING, 'gzip') self.conn.setopt(pycurl.URL, STREAM_URL) self.conn.setopt(pycurl.USERPWD, AUTH) self.conn.setopt(pycurl.WRITEFUNCTION, self.on_receive) self.conn.setopt(pycurl.HEADERFUNCTION, self.header_rcvd) while True: self.conn.perform() except Exception as ex: print "error ocurred : %s" % str(ex) def header_rcvd(self, header_data): print header_data def on_receive(self, data): temp_data = data self.buff += data if data.endswith("\r\n") and self.buff.strip(): try: tweet = json.loads(self.buff, encoding = 'UTF-8') self.buff = "" if tweet: try: self.raw_tweets.insert(tweet) except Exception as insert_ex: print "Error inserting tweet: %s" % str(insert_ex) self.count += 1 if self.count % 10 == 0: print "inserted "+str(self.count)+" tweets" except Exception as json_ex: print "json exception: %s" % str(json_ex) print repr(temp_data) stream = StreamReader()

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  • Are free operator->* overloads evil?

    - by Potatoswatter
    I was perusing section 13.5 after refuting the notion that built-in operators do not participate in overload resolution, and noticed that there is no section on operator->*. It is just a generic binary operator. Its brethren, operator->, operator*, and operator[], are all required to be non-static member functions. This precludes definition of a free function overload to an operator commonly used to obtain a reference from an object. But the uncommon operator->* is left out. In particular, operator[] has many similarities. It is binary (they missed a golden opportunity to make it n-ary), and it accepts some kind of container on the left and some kind of locator on the right. Its special-rules section, 13.5.5, doesn't seem to have any actual effect except to outlaw free functions. (And that restriction even precludes support for commutativity!) So, for example, this is perfectly legal (in C++0x, remove obvious stuff to translate to C++03): #include <utility> #include <iostream> #include <type_traits> using namespace std; template< class F, class S > typename common_type< F,S >::type operator->*( pair<F,S> const &l, bool r ) { return r? l.second : l.first; } template< class T > T & operator->*( pair<T,T> &l, bool r ) { return r? l.second : l.first; } template< class T > T & operator->*( bool l, pair<T,T> &r ) { return l? r.second : r.first; } int main() { auto x = make_pair( 1, 2.3 ); cerr << x->*false << " " << x->*4 << endl; auto y = make_pair( 5, 6 ); y->*(0) = 7; y->*0->*y = 8; // evaluates to 7->*y = y.second cerr << y.first << " " << y.second << endl; } I can certainly imagine myself giving into temp[la]tation. For example, scaled indexes for vector: v->*matrix_width[2][5] = x; Did the standards committee forget to prevent this, was it considered too ugly to bother, or are there real-world use cases?

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  • news feed using .Net Dataservices / OData / Atom ?

    - by Stephan
    Let's say I have an web CMS type application, and an EDM model with an entity called 'article', and I need to offer the ability for client applications, to a read/query the articles (and other resources stored in our database) a straightforward syndication feed of these articles to end users (along the lines of a simple RSS feed) It seems to me that for the first task, and .net 4's dataservice would be perfect for the job. For the second case, I'm wondering (a) whether atom the right format to choose - I think it is - and (b) whether it's possible to achieve such a feed using the same ado.net OData service. I took a look at some of the examples out there and briefly set up a proof of concept: http://localhost/projectname/DataService.svc/Articles <?xml version="1.0" encoding="utf-8" standalone="yes"?> <feed xml:base="http://localhost/projectname/DataService.svc/" xmlns:d="http://schemas.microsoft.com/ado/2007/08/dataservices" xmlns:m="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata" xmlns="http://www.w3.org/2005/Atom"> <title type="text">Articles</title> <id>http://localhost/projectname/DataService.svc/Articles</id> <updated>2010-05-21T09:41:22Z</updated> <link rel="self" title="Articles" href="Articles" /> <entry> <id>http://---------DataService.svc/Articles(1)</id> <title type="text"></title> <updated>2010-05-21T09:41:22Z</updated> <author> <name /> </author> <link rel="edit" title="Article" href="Articles(1)" /> <category term="Model1.Article" scheme="http://schemas.microsoft.com/ado/2007/08/dataservices/scheme" /> <content type="application/xml"> <m:properties> <d:int_ContentID m:type="Edm.Int32">1</d:int_ContentID> <d:Titel>hello world</d:Titel> <d:Source>http://www.google.com</d:Source> </m:properties> </content> </entry> </feed> and noticed that, though the feed works and items are showing up, the title tag on the entry level is left blank. (as a result, when you check this feed in a feed reader, you will see no title). I searched msdn but haven't found a way to do that, but it should be possible. Stackoverflow itself uses an atom feed in that fashion, so it should be possible. Right? So I suppose my question is; Is there a way to make the ado.net dataservice Atom feed look like something suitable for your average news feed reader? - OR, am I using the wrong tool for the wrong purposes, and should I be looking elsewhere (.net syndication API's perhaps)?

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  • Django: TypeError: 'str' object is not callable, referer: http://xxx

    - by user705415
    I've been wondering why when I set the settings.py of my django project 'arvindemo' debug = Flase and deploy it on Apache with mod_wsgi, I got the 500 Internal Server Error. Env: Django 1.4.0 Python 2.7.2 mod_wsgi 2.8 OS centOS Here is the recap: Visit the homepage, go to sub page A/B/C/D, and fill some forms, then submit it to the Apache server. Once click 'submit' button, I will get the '500 Internal Server Error', and the error_log listed below(Traceback): [Tue Apr 10 10:07:20 2012] [error] [client 122.198.133.250] Traceback (most recent call last): [Tue Apr 10 10:07:20 2012] [error] [client 122.198.133.250] File "/opt/python2.7/lib/python2.7/site-packages/django/core/handlers/wsgi.py", line 241, in __call__ [Tue Apr 10 10:07:20 2012] [error] [client 122.198.133.250] response = self.get_response(request) [Tue Apr 10 10:07:20 2012] [error] [client 122.198.133.250] File "/opt/python2.7/lib/python2.7/site-packages/django/core/handlers/base.py", line 179, in get_response [Tue Apr 10 10:07:20 2012] [error] [client 122.198.133.250] response = self.handle_uncaught_exception(request, resolver, sys.exc_info()) [Tue Apr 10 10:07:20 2012] [error] [client 122.198.133.250] File "/opt/python2.7/lib/python2.7/site-packages/django/core/handlers/base.py", line 224, in handle_uncaught_exception [Tue Apr 10 10:07:20 2012] [error] [client 122.198.133.250] if resolver.urlconf_module is None: [Tue Apr 10 10:07:20 2012] [error] [client 122.198.133.250] File "/opt/python2.7/lib/python2.7/site-packages/django/core/urlresolvers.py", line 323, in urlconf_module [Tue Apr 10 10:07:20 2012] [error] [client 122.198.133.250] self._urlconf_module = import_module(self.urlconf_name) [Tue Apr 10 10:07:20 2012] [error] [client 122.198.133.250] File "/opt/python2.7/lib/python2.7/site-packages/django/utils/importlib.py", line 35, in import_module [Tue Apr 10 10:07:20 2012] [error] [client 122.198.133.250] __import__(name) [Tue Apr 10 10:07:20 2012] [error] [client 122.198.133.250] File "/opt/web/django/arvindemo/arvindemo/../arvindemo/urls.py", line 23, in <module> [Tue Apr 10 10:07:20 2012] [error] [client 122.198.133.250] url(r'^submitPage$', name=submitPage), [Tue Apr 10 10:07:20 2012] [error] [client 122.198.133.250] TypeError: url() takes at least 2 arguments (2 given) When using django runserver, I set arvindemo.settings debug = True, everything is OK. But things changed once I set debug = Flase. Here is my views.py from django.http import HttpResponseRedirect from django.http import HttpResponse, HttpResponseServerError from django.shortcuts import render_to_response import datetime, string from user_info.models import * from django.template import Context, loader, RequestContext import settings def hello(request): return HttpResponse("hello girl") def helpPage(request): return render_to_response('kktHelp.html') def server_error(request, template_name='500.html'): return render_to_response(template_name, context_instance = RequestContext(request) ) def page404(request): return render_to_response('404.html') def submitPage(request): post = request.POST Mall = 'goodsName' Contest = 'ojs' Presentation = 'addr' WeatherReport = 'city' Habit = 'task' if Mall in post: return submitMall(request) elif Contest in post: return submitContest(request) elif Presentation in post: return submitPresentation(request) elif Habit in post: return submitHabit(request) elif WeatherReport in post: return submitWeather(request) else: return HttpResponse(request.POST) return HttpResponseRedirect('404') def submitXXX(): ..... def xxxx(): .... Here comes the urls.py from django.conf.urls import patterns, include, url from views import * from django.conf import settings handler500 = 'server_error' urlpatterns = patterns('', url(r'^hello/$', hello), # hello world url(r'^$', homePage), url(r'^time/$', getTime), url(r'^time/plus/(\d{1,2})/$', hoursAhead), url(r'^Ttime/$', templateGetTime), url(r'^Mall$', templateMall), url(r'^Contest$', templateContest), url(r'^Presentation$', templatePresentation), url(r'^Habit$', templateHabit), url(r'^Weather$', templateWeather), url(r'^Help$', helpPage), url(r'^404$', page404), url(r'^500$', server_error), url(r'^submitPage$', submitPage), url(r'^submitMall$', submitMall), url(r'^submitContest$', submitContest), url(r'^submitPresentation$', submitPresentation), url(r'^submitHabit$', submitHabit), url(r'^submitWeather$', submitWeather), url(r'^terms$', terms), url(r'^privacy$', privacy), url(r'^thanks$', thanks), url(r'^about$', about), url(r'^static/(?P<path>.*)$','django.views.static.serve',{'document_root':settings.STATICFILES_DIRS}), ) I'm sure there is no syntax error in my django project,cause when I use django runserver, everything is fine. Anyone can help ? Best regards

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  • Java Refuses to Start - Could not reserve enough space for object heap

    - by Randyaa
    Background We have a pool of aproximately 20 linux blades. Some are running Suse, some are running Redhat. ALL share NAS space which contains the following 3 folders: /NAS/app/java - a symlink that points to an installation of a Java JDK. Currently version 1.5.0_10 /NAS/app/lib - a symlink that points to a version of our application. /NAS/data - directory where our output is written All our machines have 2 processors (hyperthreaded) with 4gb of physical memory and 4gb of swap space. We limit the number of 'jobs' each machine can process at a given time to 6 (this number likely needs to change, but that does not enter into the current problem so please ignore it for the time being). Some of our jobs set a Max Heap size of 512mb, some others reserve a Max Heap size of 2048mb. Again, we realize we could go over our available memory if 6 jobs started on the same machine with the heap size set to 2048, but to our knowledge this has not yet occurred. The Problem Once and a while a Job will fail immediately with the following message: Error occurred during initialization of VM Could not reserve enough space for object heap Could not create the Java virtual machine. We used to chalk this up to too many jobs running at the same time on the same machine. The problem happened infrequently enough (MAYBE once a month) that we'd just restart it and everything would be fine. The problem has recently gotten much worse. All of our jobs which request a max heap size of 2048m fail immediately almost every time and need to get restarted several times before completing. We've gone out to individual machines and tried executing them manually with the same result. Debugging It turns out that the problem only exists for our SuSE boxes. The reason it has been happening more frequently is becuase we've been adding more machines, and the new ones are SuSE. 'cat /proc/version' on the SuSE boxes give us: Linux version 2.6.5-7.244-bigsmp (geeko@buildhost) (gcc version 3.3.3 (SuSE Linux)) #1 SMP Mon Dec 12 18:32:25 UTC 2005 'cat /proc/version' on the RedHat boxes give us: Linux version 2.4.21-32.0.1.ELsmp ([email protected]) (gcc version 3.2.3 20030502 (Red Hat Linux 3.2.3-52)) #1 SMP Tue May 17 17:52:23 EDT 2005 'uname -a' gives us the following on BOTH types of machines: UTC 2005 i686 i686 i386 GNU/Linux No jobs are running on the machine, and no other processes are utilizing much memory. All of the processes currently running might be using 100mb total. 'top' currently shows the following: Mem: 4146528k total, 3536360k used, 610168k free, 132136k buffers Swap: 4194288k total, 0k used, 4194288k free, 3283908k cached 'vmstat' currently shows the following: procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu---- r b swpd free buff cache si so bi bo in cs us sy id wa 0 0 0 610292 132136 3283908 0 0 0 2 26 15 0 0 100 0 If we kick off a job with the following command line (Max Heap of 1850mb) it starts fine: java/bin/java -Xmx1850M -cp helloworld.jar HelloWorld Hello World If we bump up the max heap size to 1875mb it fails: java/bin/java -Xmx1875M -cp helloworld.jar HelloWorld Error occurred during initialization of VM Could not reserve enough space for object heap Could not create the Java virtual machine. It's quite clear that the memory currently being used is for Buffering/Caching and that's why so little is being displayed as 'free'. What isn't clear is why there is a magical 1850mb line where anything higher means Java can't start. Any explanations would be greatly appreciated.

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  • Throwing a C++ exception from inside a Linux Signal handler

    - by SoapBox
    As a thought experiment more than anything I am trying to get a C++ exception thrown "from" a linux signal handler for SIGSEGV. (I'm aware this is not a solution to any real world SIGSEGV and should never actually be done, but I thought I would try it out after being asked about it, and now I can't get it out of my head until I figure out how to do it.) Below is the closest I have come, but instead of the signal being caught properly, terminate() is being called as if no try/catch block is available. Anyone know why? Or know a way I can actually get a C++ exception from a signal handler? The code (beware, the self modifying asm limits this to running on x86_64 if you're trying to test it): #include <iostream> #include <stdexcept> #include <signal.h> #include <stdint.h> #include <errno.h> #include <string.h> #include <sys/mman.h> using namespace std; uint64_t oldaddr = 0; void thrower() { cout << "Inside thrower" << endl; throw std::runtime_error("SIGSEGV"); } void segv_handler(int sig, siginfo_t *info, void *pctx) { ucontext_t *context = (ucontext_t *)pctx; cout << "Inside SIGSEGV handler" << endl; oldaddr = context->uc_mcontext.gregs[REG_RIP]; uint32_t pageSize = (uint32_t)sysconf(_SC_PAGESIZE); uint64_t bottomOfOldPage = (oldaddr/pageSize) * pageSize; mprotect((void*)bottomOfOldPage, pageSize*2, PROT_READ|PROT_WRITE|PROT_EXEC); // 48 B8 xx xx xx xx xx xx xx xx = mov rax, xxxx *((uint8_t*)(oldaddr+0)) = 0x48; *((uint8_t*)(oldaddr+1)) = 0xB8; *((int64_t*)(oldaddr+2)) = (int64_t)thrower; // FF E0 = jmp rax *((uint8_t*)(oldaddr+10)) = 0xFF; *((uint8_t*)(oldaddr+11)) = 0xE0; } void func() { try { *(uint32_t*)0x1234 = 123456789; } catch (...) { cout << "caught inside func" << endl; throw; } } int main() { cout << "Top of main" << endl; struct sigaction action, old_action; action.sa_sigaction = segv_handler; sigemptyset(&action.sa_mask); action.sa_flags = SA_SIGINFO | SA_RESTART | SA_NODEFER; if (sigaction(SIGSEGV, &action, &old_action)<0) cerr << "Error setting handler : " << strerror(errno) << endl; try { func(); } catch (std::exception &e) { cout << "Caught : " << e.what() << endl; } cout << "Bottom of main" << endl << endl; } The actual output: Top of main Inside SIGSEGV handler Inside thrower terminate called after throwing an instance of 'std::runtime_error' what(): SIGSEGV Aborted Expected output: Top of main Inside thrower caught inside func Caught : SIGSEGV Bottom of main

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  • Evidence-Based-Scheduling - are estimations only as accurate as the work-plan they're based on?

    - by Assaf Lavie
    I've been using FogBugz's Evidence Based Scheduling (for the uninitiated, Joel explains) for a while now and there's an inherent problem I can't seem to work around. The system is good at telling me the probability that a given project will be delivered at some date, given the detailed list of tasks that comprise the project. However, it does not take into account the fact that during development additional tasks always pop up. Now, there's the garbage-can approach of creating a generic task/scheduled-item for "last minute hacks" or "integration tasks", or what have you, but that clearly goes against the idea of aggregating the estimates of many small cases. It's often the case that during the development stage of a project you realize that there's a whole area your planning didn't cover, because, well, that's the nature of developing stuff that hasn't been developed before. So now your ~3 month project may very well turn into a 6 month project, but not because your estimations were off (you could be the best estimator in the world, for those task the comprised your initial work plan); rather because you ended up adding a whole bunch of new tasks that weren't there to begin with. EBS doesn't help you with that. It could, theoretically (I guess). It could, perhaps, measure the amount of work you add to a project over time and take that into consideration when estimating the time remaining on a given project. Just a thought. In other words, EBS works on a task basis, but not on a project/release basis - but the latter is what's important. It's what your boss typically cares about - delivery date, not the time it takes to finish each task along the way, and not the time it would have taken, if your planning was perfect. So the question is (yes, there's a question here, don't close it): What's your methodology when it comes to using EBS in FogBugz and how do you solve the problem above, which seems to be a main cause of schedule delays and mispredictions? Edit Some more thoughts after reading a few answers: If it comes down to having to choose which delivery date you're comfortable presenting to your higher-ups by squinting at the delivery-probability graph and choosing 80%, or 95%, or 60% (based on what, exactly?) then we've resorted to plain old buffering/factoring of our estimates. In which case, couldn't we have skipped the meticulous case by case hour-sized estimation effort step? By forcing ourselves to break down tasks that take more than a day into smaller chunks of work haven't we just deluded ourselves into thinking our planning is as tight and thorough as it could be? People may be consistently bad estimators that do not even learn from their past mistakes. In that respect, having an EBS system is certainly better than not having one. But what can we do about the fact that we're not that good in planning as well? I'm not sure it's a problem that can be solved by a similar system. Our estimates are wrong because of tendencies to be overly optimistic/pessimistic about certain tasks, and because of neglect to account for systematic delays (e.g. sick days, major bug crisis) - and usually not because we lack knowledge about the work that needs to be done. Our planning, on the other hand, is often incomplete because we simply don't have enough knowledge in this early stage; and I don't see how an EBS-like system could fill that gap. So we're back to methodology. We need to find a way to accommodate bad or incomplete work plans that's better than voodoo-multiplication.

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  • What container type provides better (average) performance than std::map?

    - by Truncheon
    In the following example a std::map structure is filled with 26 values from A - Z (for key) and 0 - 26 for value. The time taken (on my system) to lookup the last entry (10000000 times) is roughly 250 ms for the vector, and 125 ms for the map. (I compiled using release mode, with O3 option turned on for g++ 4.4) But if for some odd reason I wanted better performance than the std::map, what data structures and functions would I need to consider using? I apologize if the answer seems obvious to you, but I haven't had much experience in the performance critical aspects of C++ programming. UPDATE: This example is rather trivial and hides the true complexity of what I'm trying to achieve. My real world project is a simple scripting language that uses a parser, data tree, and interpreter (instead of a VM stack system). I need to use some kind of data structure (perhaps map) to store the variables names created by script programmers. These are likely to be pretty randomly named, so I need a lookup method that can quickly find a particular key within a (probably) fairly large list of names. #include <ctime> #include <map> #include <vector> #include <iostream> struct mystruct { char key; int value; mystruct(char k = 0, int v = 0) : key(k), value(v) { } }; int find(const std::vector<mystruct>& ref, char key) { for (std::vector<mystruct>::const_iterator i = ref.begin(); i != ref.end(); ++i) if (i->key == key) return i->value; return -1; } int main() { std::map<char, int> mymap; std::vector<mystruct> myvec; for (int i = 'a'; i < 'a' + 26; ++i) { mymap[i] = i - 'a'; myvec.push_back(mystruct(i, i - 'a')); } int pre = clock(); for (int i = 0; i < 10000000; ++i) { find(myvec, 'z'); } std::cout << "linear scan: milli " << clock() - pre << "\n"; pre = clock(); for (int i = 0; i < 10000000; ++i) { mymap['z']; } std::cout << "map scan: milli " << clock() - pre << "\n"; return 0; }

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  • Trying get dynamic content hole-punched through Magento's Full Page Cache

    - by rlflow
    I am using Magento Enterprise 1.10.1.1 and need to get some dynamic content on our product pages. I am inserting the current time in a block to quickly see if it is working, but can't seem to get through full page cache. I have tried a variety of implementations found here: http://tweetorials.tumblr.com/post/10160075026/ee-full-page-cache-hole-punching http://oggettoweb.com/blog/customizations-compatible-magento-full-page-cache/ http://magentophp.blogspot.com/2011/02/magento-enterprise-full-page-caching.html (http://www.exploremagento.com/magento/simple-custom-module.php - custom module) Any solutions, thoughts, comments, advice is welcome. here is my code: app/code/local/Fido/Example/etc/config.xml <?xml version="1.0"?> <config> <modules> <Fido_Example> <version>0.1.0</version> </Fido_Example> </modules> <global> <blocks> <fido_example> <class>Fido_Example_Block</class> </fido_example> </blocks> </global> </config> app/code/local/Fido/Example/etc/cache.xml <?xml version="1.0" encoding="UTF-8"?> <config> <placeholders> <fido_example> <block>fido_example/view</block> <name>example</name> <placeholder>CACHE_TEST</placeholder> <container>Fido_Example_Model_Container_Cachetest</container> <cache_lifetime>86400</cache_lifetime> </fido_example> </placeholders> </config> app/code/local/Fido/Example/Block/View.php <?php /** * Example View block * * @codepool Local * @category Fido * @package Fido_Example * @module Example */ class Fido_Example_Block_View extends Mage_Core_Block_Template { private $message; private $att; protected function createMessage($msg) { $this->message = $msg; } public function receiveMessage() { if($this->message != '') { return $this->message; } else { $this->createMessage('Hello World'); return $this->message; } } protected function _toHtml() { $html = parent::_toHtml(); if($this->att = $this->getMyCustom() && $this->getMyCustom() != '') { $html .= '<br />'.$this->att; } else { $now = date('m-d-Y h:i:s A'); $html .= $now; $html .= '<br />' ; } return $html; } } app/code/local/Fido/Example/Model/Container/Cachetest.php <?php class Fido_Example_Model_Container_Cachetest extends Enterprise_PageCache_Model_Container_Abstract { protected function _getCacheId() { return 'HOMEPAGE_PRODUCTS' . md5($this->_placeholder->getAttribute('cache_id') . $this->_getIdentifier()); } protected function _renderBlock() { $blockClass = $this->_placeholder->getAttribute('block'); $template = $this->_placeholder->getAttribute('template'); $block = new $blockClass; $block->setTemplate($template); return $block->toHtml(); } protected function _saveCache($data, $id, $tags = array(), $lifetime = null) { return false; } } app/design/frontend/enterprise/[mytheme]/template/example/view.phtml <?php /** * Fido view template * * @see Fido_Example_Block_View * */ ?> <div> <?php echo $this->receiveMessage(); ?> </span> </div> snippet from app/design/frontend/enterprise/[mytheme]/layout/catalog.xml <reference name="content"> <block type="catalog/product_view" name="product.info" template="catalog/product/view.phtml"> <block type="fido_example/view" name="product.info.example" as="example" template="example/view.phtml" />

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  • Where do I start ?

    - by Panthe
    Brief History: Just graduated high school, learned a bit of python and C++, have no friends with any helpful computer knowledge at all. Out of anyone i met in my school years I was probably the biggest nerd, but no one really knew. I consider my self to have a vast amount of knowledge on computers and tech then the average person. built/fixed tons of computers, and ability to troubleshoot pretty much any problem I came across. Now that high school is over, Ive really been thinking about my career. Loving, living computers for the past 15 years of my life I decided to take my ability's and try to learn computer programming, why I didn't start earlier I don't know, seems to be big mistake on my part... Doing some research I concluded that Python was the first programming language I should learn, since it was high level and easier to understand then C++ and Java. I also knew that to become good at what I did I needed to know more then just 2 or 3 languages, which didn't seem like a big problem considering once I learned the way Python worked, mainly syntax changed, and the rest would come naturally. I watched a couple of youtube videos, downloaded some book pdf's and snooped around from some tutorials here and there to get the hang of what to do. A two solid weeks had passed of trying to understand the syntax, create small programs that used the basic functions and understanding how it worked, I think i have got the hang of it. It breaks down into what ive been dealing with all this time (although i kinda knew) is that, input,output, loops, functions and other things derived from 0's and 1's storing data and recalling it, ect. (A VERY BASIC IDEA). Ive been able to create small programs, Hangman, file storing, temperature conversion, Caeser Cipher decode/encoding, Fibonacci Sequence and more, which i can create and understand how each work. Being 2 weeks into this, I have learned alot. Nothing at all compared to what i should be learning in the years to come if i get a grip on what I'm doing. While doing these programs I wont stop untill I've done doing a practice problem on a book, which embarresing enough will take me a couple hour depending on the complexity of it. I absolutly will not put aside the challenge until its complete, WHICH CAN BE EXTREMELY DRAINING, ive tried most problems without cheating and reached success, which makes me feel extremely proud of my self after completing something after much trial and error. After all this I have met the demon, alogrithm's which seem to be key to effiecent code. I cant seem to rap my head around some of the computer codes people put out there using numbers, and sometimes even basic functions, I have been able to understand them after a while but i know there are alot more complex things to come, considering my self smart, functions that require complex codes, actually hurt my brain. NOTHING EVER IN LIFE HURT MY BRAIN....... not even math classes in highschool, trying to understand some of the stuff people put out there makes me feel like i have a mental disadvantage lol... i still walk forward though, crossing my fingers that the understanding will come with time. Sorry if is this is long i just wish someone takes all these things into consideration when answering my question. even through all these downsides im still pushing through and continuing to try and get good at this, i know reading these tutorials wont make me any good unless i can become creative and make my own, understand other peoples programs, so this leads me to the simple question i could have asked in the beginning..... WHERE IN THE WORLD DO I START ? Ive been trying to find out how to understand some of the open source projects, how i can work with experianced coders to learn from them and help them, but i dont think thats even possible by the way how far people's knowledge is compared to me, i have no freinds who i can learn from, can someone help me and guide me into the right direction.. i have a huge motivation to get good at coding, anything information would be extremely helpful

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  • jQuery: Div elements are not showing up

    - by Legend
    I am adapting the Coverflow technique to work with a div. Following is the html: <html> <head> <meta http-equiv="Content-type" content="text/html; charset=utf-8" /> <style type="text/css" media="screen"> body,html { margin: 0; padding: 0; background: #000; height: 100%; color: #eee; font-family: Arial; font-size: 10px; } div.magnifyme { height: 80px; padding: 80px; position: absolute; top: 0px; left: 0px; width: 8000px; } div.wrapper { margin: 0px; height: 470px; /*border: 2px solid #999;*/ overflow: hidden; padding-left: 40px; right: 1px; width: 824px; position: relative; } div.container {position: relative; width: 854px; height: 480px; background: #000; margin: auto;} div.nav {position: absolute; top: 10px; width: 20%; height: 10%; right: 1px; } div.magnifyme div { position: absolute; width: 300px; height: 280px; float: left; margin: 5px; position: relative; border: 2px solid #999; background: #500; } </style> <script type="text/javascript" src="jquery-1.3.2.js"></script> <script type="text/javascript" src="ui.coverflow.js"></script> <script type="text/javascript"> $(function() { $("div.magnifyme").coverflow(); $("#add").click(function() { location.reload(); $(".magnifyme").append("<div id=\"div5\">hello world</div>"); $("div.magnifyme").coverflow(); }); }); </script> </head> <body> <div class="container"> <div class="wrapper"> <div class="magnifyme"> <div id="div0">This is div 0</div> <div id="div1">This is div 1</div> <div id="div2">This is div 2</div> <div id="div3">This is div 3</div> <div id="div4">This is div 4</div> </div> </div> <div class="nav"> <button type="button" id="add">Add to Deck</button> </div> </div> </body> </html> The coverflow function (included as a js file in the head section) is here. When I click the button, I was expecting it to add a DIV to the already present deck. For some reason, it doesn't show the newly added DIV. I tried calling the coverflow() function after I added the new element but that didn't work either. Is there any way I can make this work?

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  • xsl:include fails after upgrading PHP version; is libxml/libxslt version mismatch the issue?

    - by Wiseguy
    I'm running Windows XP with the precompiled PHP binaries available from windows.php.net. I upgraded from PHP 5.2.5 to PHP 5.2.16, and now the xsl:includes in some of my stylesheets stopped working. Testing each version in succession, I discovered that it worked up through 5.2.8 and does not work in 5.2.9+. I now get the following three errors for each xsl:include. Warning: XSLTProcessor::importStylesheet() [xsltprocessor.importstylesheet]: I/O warning : failed to load external entity "file%3A/C%3A/path/to/included/stylesheet.xsl" in ... on line 227 Warning: XSLTProcessor::importStylesheet() [xsltprocessor.importstylesheet]: compilation error: file file%3A//C%3A/path/to/included/stylesheet.xsl line 36 element include in ... on line 227 Warning: XSLTProcessor::importStylesheet() [xsltprocessor.importstylesheet]: xsl:include : unable to load file%3A/C%3A/path/to/included/stylesheet.xsl in ... on line 227 I presume this is because it cannot find the specified file. Many of the includes are in the same directory as the stylesheet being transformed and have no directory in the path, i.e. <xsl:include href="fileInSameDir.xsl">. Interestingly, in the first and third errors, it is displaying the file:// protocol with only one slash instead of the correct two. I'm guessing that's the problem. (When I hard-code a full path using "file:/" it fails, but when I hard-code a full path with "file://" it works.) But what could cause that? A bug in libxslt/libxml? I also found an apparent version mismatch between libxml and the version of libxml that libxslt was compiled against. 5.2.5 libxml Version = 2.6.26 libxslt compiled against libxml Version = 2.6.26 5.2.8 libxml Version = 2.6.32 libxslt compiled against libxml Version = 2.6.32 === it breaks in versions starting at 5.2.9 === 5.2.9 libxml Version = 2.7.3 libxslt compiled against libxml Version = 2.6.32 5.2.16 libxml Version = 2.7.7 libxslt compiled against libxml Version = 2.6.32 Up until PHP 5.2.9, libxslt was compiled against the same version of libxml that was included with PHP. But starting with PHP 5.2.9, libxslt was compiled against an older version of libxml than that which was included with PHP. Is this a problem with the distributed binaries or just a coincidence? To test this, I imagine PHP could be built with different versions of libxml/libxslt to see which combinations work or don't. Unfortunately, I'm out of my element in a Windows world, and building PHP on Windows seems over my head. Regrettably, I've been thus far unable to reproduce this problem with an example outside my app, so I'm struggling to narrow it down and can't submit a specific bug. So, do you think it is caused by a version mismatch problem in the distributed binaries? a bug introduced in PHP 5.2.9? a bug introduced in libxml 2.7? something else? I'm stumped. Any thoughts that could point me in the right direction are greatly appreciated. Thanks.

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  • Help with Silverlight Sockets and Message delivery

    - by pixel3cs
    There are 4 months since I stopped developing my Silverlight Multiplayer Chess game. The problem was a bug wich I couldn't reproduce. Sice I got some free time this week I managed to discover the problem and I am now able to reproduce the bug. It seems that if I send 10 messages from client, one after another, with no delay between them, just like in the below example // when I press Enter, the client will 10 messages with no delay between them private void textBox_KeyDown(object sender, KeyEventArgs e) { if (e.Key == Key.Enter && textBox.Text.Length > 0) { for (int i = 0; i < 10; i++) { MessageBuilder mb = new MessageBuilder(); mb.Writer.Write((byte)GameCommands.NewChatMessageInTable); mb.Writer.Write(string.Format("{0}{2}: {1}", ClientVars.PlayerNickname, textBox.Text, i)); SendChatMessageEvent(mb.GetMessage()); //System.Threading.Thread.Sleep(100); } textBox.Text = string.Empty; } } // the method used by client to send a message to server public void SendData(Message message) { if (socket.Connected) { SocketAsyncEventArgs myMsg = new SocketAsyncEventArgs(); myMsg.RemoteEndPoint = socket.RemoteEndPoint; byte[] buffer = message.Buffer; myMsg.SetBuffer(buffer, 0, buffer.Length); socket.SendAsync(myMsg); } else { string err = "Server does not respond. You are disconnected."; socket.Close(); uiContext.Post(this.uiClient.ProcessOnErrorData, err); } } // the method used by server to receive data from client private void OnDataReceived(IAsyncResult async) { ClientSocketPacket client = async.AsyncState as ClientSocketPacket; int count = 0; try { if (client.Socket.Connected) count = client.Socket.EndReceive(async); // THE PROBLEM IS HERE // IF SERVER WAS RECEIVE ALL MESSAGES SEPARATELY, ONE BY ONE, THE COUNT // WAS ALWAYS 15, BUT BECAUSE THE SERVER RECEIVE 3 MESSAGES IN 1, THE COUNT // IS SOMETIME 45 } catch { HandleException(client); } client.MessageStream.Write(client.Buffer, 0, count); Message message; while (client.MessageStream.Read(out message)) { message.Tag = client; ThreadPool.QueueUserWorkItem(new WaitCallback(this.processingThreadEvent.ServerGotData), message); totalReceivedBytes += message.Buffer.Length; } try { if (client.Socket.Connected) client.Socket.BeginReceive(client.Buffer, 0, client.Buffer.Length, 0, new AsyncCallback(OnDataReceived), client); } catch { HandleException(client); } } there are sent only 3 big messages, and every big message contain 3 or 4 small messages. This is not the behavior I want. If I put a 100 milliseconds delay between message delivery, everything is work fine, but in a real world scenario users can send messages to server even at 1 millisecond between them. Are there any settings to be done in order to make the client send only one message at a time, or Even if I receive 3 messages in 1, are they full messages all the time (I dont't want to receive 2.5 messages in one big message) ? because if they are, I can read them and treat this new situation

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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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  • Javascript phsyics in a 2d space

    - by eroo
    So, I am working on teaching myself Canvas (HTML5) and have most of a simple game engine coded up. It is a 2d representation of a space scene (planets, stars, celestial bodies, etc). My default "Sprite" class has a frame listener like such: "baseClass" contains a function that allows inheritance and applies "a" to "this.a". So, "var aTest = new Sprite({foo: 'bar'});" would make "aTest.foo = 'bar'". This is how I expose my objects to each other. { Sprite = baseClass.extend({ init: function(a){ baseClass.init(this, a); this.fields = new Array(); // list of fields of gravity one is in. Not sure if this is a good idea. this.addFL(function(tick){ // this will change to be independent of framerate soon. // and this is where I need help // gobjs is an array of all the Sprite objects in the "world". for(i = 0; i < gobjs.length; i++){ // Make sure its got setup correctly, make sure it -wants- gravity, and make sure it's not -this- sprite. if(typeof(gobjs[i].a) != undefined && !gobjs[i].a.ignoreGravity && gobjs[i].id != this.id){ // Check if it's within a certain range (obviously, gravity doesn't work this way... But I plan on having a large "space" area, // And I can't very well have all objects accounted for at all times, can I? if(this.distanceTo(gobjs[i]) < this.s.size*10 && gobjs[i].fields.indexOf(this.id) == -1){ gobjs[i].fields.push(this.id); } } } for(i = 0; i < this.fields.length; i++){ distance = this.distanceTo(gobjs[this.fields[i]]); angletosun = this.angleTo(gobjs[this.fields[i]])*(180/Math.PI); // .angleTo works very well, returning the angle in radians, which I convert to degrees here. // I have no idea what should happen here, although through trial and error (and attempting to read Maths papers on gravity (eeeeek!)), this sort of mimics gravity. // angle is its orientation, currently I assign a constant velocity to one of my objects, and leave the other static (it ignores gravity, but still emits it). this.a.angle = angletosun+(75+(distance*-1)/5); //todo: omg learn math if(this.distanceTo(gobjs[this.fields[i]]) > gobjs[this.fields[i]].a.size*10) this.fields.splice(i); // out of range, stop effecting. } }); } }); } Thanks in advance. The real trick is that one line: { this.a.angle = angletosun+(75+(distance*-1)/5); } This is more a physics question than Javascript, but I've searched and searched and read way to many wiki articles on orbital mathematics. It gets over my head very quickly. Edit: There is a weirdness with the SO formatting; forgives me, I is noobie.

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  • Decentralized synchronized secure data storage

    - by Alberich
    Introduction Hi, I am going to ask a question which seems utopic for me, but I need to know if there is a way to achieve what I need. And if not, I need to know why not. The idea Suppose I have a database structure, in MySql. I want to create some solution to allow anyone (no matter who, no matter where) to have a synchronized copy (updated clone) of this database (with its content) Well, and it is not going to be just one synchronized copy, it could (and should) be a multiple replication (supposing the basic, this means, for example, ten copies all over the world) And, the most important thing: It must be secure. By secure I mean only real-accepted transactions will be synchronized with all the others (no matter how many) database copies/clones. Note: Since it would be quite difficult to make the synchronization in real-time, I will design everything to make this feature dispensable. So it is not required. My auto-suggestion This is how I am thinking to manage it: Time identifiers and Updates checking: Every action (insert, update, delete...) will be stored as the action instruction itself, associated to the time identifier. [I think better than a DATETIME field, it'll be an INT one, with the number of miliseconds passed from 1st january 2013 on, for example]. So each copy is going to ask to the "neighbour copy" for new actions done since last update, and execute them after checking they are allowed. Problem 1: the "neighbour copy" could be outdated too. Solution 1: do not ask just one neighbour, create a random list with some of the copies/clones and ask them for news (I could avoid the list and ask ALL the clones for updates, but this will be inefficient if clones number ascends too much). Problem 2: Real-time global synchronization is not active. What if... Someone at CLONE_ENTERPRISING inserts a row into TABLE. ... this row goes to every clone ... Someone at CLONE_FIXEMALL deletes this row. ... and at the same time, somewhere in an outdated clone ... Someone at CLONE_DROPOUT edits this row (now inexistent at the other clones) Solution 2: easy stuff, force a GLOBAL synchronization before doing any new "depending-on-third-data action" (edit, for example). This global synch. will be unnecessary when making an INSERT, for instance. Note: Well, someone could have some fun, and make the same insert in two clones... since they're not getting updated in real-time, this row will exist twice. But, it's the same as when we have one single database, in some needed cases we check if there is an existing same-row before doing the final action. Not a problem. Problem 3: It is possible to edit the code and do not filter actions, so someone could spread instructions to delete everything, or just make some trolling activity. This is not a problem, since good clones will always be somewhere. Those who got bad won't interest anymore. I really appreciate if you read. I know this is not the perfect solution, it has possibly hundred of holes, but it is my basic start. I will now appreciate anything you can teach me now. Thanks a lot. PS.: It could be that all this I am trying already exists and has its own name. Sorry for asking then (I'd anyway thank this name, if it exists)

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  • Recommended integration mechanism for bi-directional, authenticated, encrypted connection in C clien

    - by rcampbell
    Let me first give an example. Imagine you have a single server running a JVM application. This server keeps a collection of N equations, once for each client: Client #1: 2x Client #2: 1 + y Client #3: z/4 This server includes an HTTP interface so that random visitors can type https://www.acme.com/client/3 int their browsers and see the latest evaluated result of z/4. The tricky part is that either the client or the server may change the variable value at any time, informing the other party immediately. More specifically, Client #3 - a C app - can initially tell the server that z = 20. An hour later that same client informs the server that z = 23. Likewise the server can later inform the client that z = 28. As caf pointed out in the comments, there can be a race condition when values are changed by the client and server simultaneously. The solution would be for both client and server to send the operation performed in their message, which would need to be executed by the other party. To keep things simple, let's limit the operations to (commutative) addition, allowing us to disregard message ordering. For example, the client seeds the server with z = 20: server:z=20, client:z=20 server sends {+3} message (so z=23 locally) & client sends {-2} message (so z=18 locally) at the exact same time server receives {-2} message at some point, adds to his local copy so z=21 client receives {+3} message at some point, adds to his local copy so z=21 As long as all messages are eventually evaluated by both parties, the correct answer will eventually be given to the users of the client and server since we limited ourselves to commutative operations (addition of 3 and -2). This does mean that both client and server can be returning incorrect answers in the time it takes for messages to be exchanged and processed. While undesirable, I believe this is unavoidable. Some possible implementations of this idea include: Open an encrypted, always on TCP socket connection for communication Pros: no additional infrastructure needed, client and server know immediately if there is a problem (disconnect) with the other party, fairly straightforward (except the the encryption), native support from both JVM and C platforms Cons: pretty low-level so you end up writing a lot yourself (protocol, delivery verification, retry-on-failure logic), probably have a lot of firewall headaches during client app installation Asynchronous messaging (ex: ActiveMQ) Pros: transactional, both C & Java integration, free up the client and server apps from needing retry logic or delivery verification, pretty straightforward encryption, easy extensibility via message filters/routers/etc Cons: need additional infrastructure (message server) which must never fail, Database or file system as asynchronous integration point Same pros/cons as above but messier RESTful Web Service Pros: simple, possible reuse of the server's existing REST API, SSL figures out the encryption problem for you (maybe use RSA key a la GitHub for authentication?) Cons: Client now needs to run a C HTTP REST server w/SSL, client and server need retry logic. Axis2 has both a Java and C version, but you may be limited to SOAP. What other techniques should I be evaluating? What real world experiences have you had with these mechanisms? Which do you recommend for this problem and why?

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  • Are there supposed to be more restrictions on operator->* overloads?

    - by Potatoswatter
    I was perusing section 13.5 after refuting the notion that built-in operators do not participate in overload resolution, and noticed that there is no section on operator->*. It is just a generic binary operator. Its brethren, operator->, operator*, and operator[], are all required to be non-static member functions. This precludes definition of a free function overload to an operator commonly used to obtain a reference from an object. But the uncommon operator->* is left out. In particular, operator[] has many similarities. It is binary (they missed a golden opportunity to make it n-ary), and it accepts some kind of container on the left and some kind of locator on the right. Its special-rules section, 13.5.5, doesn't seem to have any actual effect except to outlaw free functions. (And that restriction even precludes support for commutativity!) So, for example, this is perfectly legal (in C++0x, remove obvious stuff to translate to C++03): #include <utility> #include <iostream> #include <type_traits> using namespace std; template< class F, class S > typename common_type< F,S >::type operator->*( pair<F,S> const &l, bool r ) { return r? l.second : l.first; } template< class T > T & operator->*( pair<T,T> &l, bool r ) { return r? l.second : l.first; } template< class T > T & operator->*( bool l, pair<T,T> &r ) { return l? r.second : r.first; } int main() { auto x = make_pair( 1, 2.3 ); cerr << x->*false << " " << x->*4 << endl; auto y = make_pair( 5, 6 ); y->*(0) = 7; y->*0->*y = 8; // evaluates to 7->*y = y.second cerr << y.first << " " << y.second << endl; } I can certainly imagine myself giving into temp[la]tation. For example, scaled indexes for vector: v->*matrix_width[5] = x; Did the standards committee forget to prevent this, was it considered too ugly to bother, or are there real-world use cases?

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