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• php form submit and the resend infromation screen

  - by Para

  Hello, I want to ask a best practice question. Suppose I have a form in php with 3 fields say name, email and comment. I submit the form via POST. In PHP I try and insert the date into the database. Suppose the insertion fails. I should now show the user an error and display the form filled in with the data he previously inserted so he can correct his error. Showing the form in it's initial state won't do. So I display the form and the 3 fields are now filled in from PHP with echo or such. Now if I click refresh I get a message saying "Are you sure you want to resend information?". OK. Suppose after I insert the data I don't carry on but I redirect to the same page but with the necessary parameters in the query string. This makes the message go away but I have to carry 3 parameters in the query string. So my question is: How is it better to do this? I want to not carry around lots of parameters in the query string but also not get that error. How can this be done? Should I use cookies to store the form information.

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• C - dns query to structure

  - by Bibo

  I have these structures: typedef struct dnsQuery { char header[12]; struct dnsQuerySection *querySection; } TdnsQuery; typedef struct dnsQuerySection { unsigned char *name; struct dnsQueryQuestion *question; } TdnsQuerySection; typedef struct dnsQueryQuestion { unsigned short qtype; unsigned short qclass; } TdnsQueryQuestion; and I have dns query in byte array from recvfrom. I am trying to get structure from byte array like this: TdnsQuery* dnsQuery = (TdnsQuery*)buf; When I tried to access qtype like this: printf("%u", dnsQuery->querySection->question.qtype); I get seg fault 11. Can someone help me with these structures? What´s wrong with them? I tried to add structure: typedef struct udpPacket { char header[8]; structr dnsQuery query; } and mapped this structure from byte array but it didn´t help. Can someone help me with these structures? How they should look like for dns query with udp protocol?

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• How to encapsulate a WinAPI application into a C++ class

  - by Semen Semenych

  There is a simple WinAPI application. All it does currently is this: register a window class register a tray icon with a menu create a value in the registry in order to autostart and finally, it checks if it's unique using a mutex As I'm used to writing code mainly in C++, and no MFC is allowed, I'm forced to encapsulate this into C++ classes somehow. So far I've come up with such a design: there is a class that represents the application it keeps all the wndclass, hinstance, etc variables, where the hinstance is passed as a constructor parameter as well as the icmdshow and others (see WinMain prototype) it has functions for registering the window class, tray icon, reigstry information it encapsulates the message loop in a function In WinMain, the following is done: Application app(hInstance, szCmdLIne, iCmdShow); return app.exec(); and the constructor does the following: registerClass(); registerTray(); registerAutostart(); So far so good. Now the question is : how do I create the window procedure (must be static, as it's a c-style pointer to a function) AND keep track of what the application object is, that is, keep a pointer to an Application around. The main question is : is this how it's usually done? Am I complicating things too much? Is it fine to pass hInstance as a parameter to the Application constructor? And where's the WndProc? Maybe WndProc should be outside of class and the Application pointer be global? Then WndProc invokes Application methods in response to various events.

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• ControlCollection extension method optimization

  - by Johan Leino

  Hi, got question regarding an extension method that I have written that looks like this: public static IEnumerable<T> FindControlsOfType<T>(this ControlCollection instance) where T : class { T control; foreach (Control ctrl in instance) { if ((control = ctrl as T) != null) { yield return control; } foreach (T child in FindControlsOfType<T>(ctrl.Controls)) { yield return child; } } } public static IEnumerable<T> FindControlsOfType<T>(this ControlCollection instance, Func<T, bool> match) where T : class { return FindControlsOfType<T>(instance).Where(match); } The idea here is to find all controls that match a specifc criteria (hence the Func<..) in the controls collection. My question is: Does the second method (that has the Func) first call the first method to find all the controls of type T and then performs the where condition or does the "runtime" optimize the call to perform the where condition on the "whole" enumeration (if you get what I mean). secondly, are there any other optimizations that I can do to the code to perform better. An example can look like this: var checkbox = this.Controls.FindControlsOfType<MyCustomCheckBox>( ctrl => ctrl.CustomProperty == "Test" ) .FirstOrDefault();

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• WCF data services (OData), query with inheritance limitation?

  - by Mathieu Hétu

  Project: WCF Data service using internally EF4 CTP5 Code-First approach. I configured entities with inheritance (TPH). See previous question on this topic: Previous question about multiple entities- same table The mapping works well, and unit test over EF4 confirms that queries runs smoothly. My entities looks like this: ContactBase (abstract) Customer (inherits from ContactBase), this entity has also several Navigation properties toward other entities Resource (inherits from ContactBase) I have configured a discriminator, so both Customer and Resource map to the same table. Again, everythings works fine on the Ef4 point of view (unit tests all greens!) However, when exposing this DBContext over WCF Data services, I get: - CustomerBases sets exposed (Customers and Resources sets seems hidden, is it by design?) - When I query over Odata on Customers, I get this error: Navigation Properties are not supported on derived entity types. Entity Set 'ContactBases' has a instance of type 'CodeFirstNamespace.Customer', which is an derived entity type and has navigation properties. Please remove all the navigation properties from type 'CodeFirstNamespace.Customer'. Stacktrace: at System.Data.Services.Serializers.SyndicationSerializer.WriteObjectProperties(IExpandedResult expanded, Object customObject, ResourceType resourceType, Uri absoluteUri, String relativeUri, SyndicationItem item, DictionaryContent content, EpmSourcePathSegment currentSourceRoot) at System.Data.Services.Serializers.SyndicationSerializer.WriteEntryElement(IExpandedResult expanded, Object element, ResourceType expectedType, Uri absoluteUri, String relativeUri, SyndicationItem target) at System.Data.Services.Serializers.SyndicationSerializer.<DeferredFeedItems>d__b.MoveNext() at System.ServiceModel.Syndication.Atom10FeedFormatter.WriteItems(XmlWriter writer, IEnumerable`1 items, Uri feedBaseUri) at System.ServiceModel.Syndication.Atom10FeedFormatter.WriteFeedTo(XmlWriter writer, SyndicationFeed feed, Boolean isSourceFeed) at System.ServiceModel.Syndication.Atom10FeedFormatter.WriteFeed(XmlWriter writer) at System.ServiceModel.Syndication.Atom10FeedFormatter.WriteTo(XmlWriter writer) at System.Data.Services.Serializers.SyndicationSerializer.WriteTopLevelElements(IExpandedResult expanded, IEnumerator elements, Boolean hasMoved) at System.Data.Services.Serializers.Serializer.WriteRequest(IEnumerator queryResults, Boolean hasMoved) at System.Data.Services.ResponseBodyWriter.Write(Stream stream) Seems like a limitation of WCF Data services... is it? Not much documentation can be found on the web about WCF Data services (OData) and inheritance specifications. How can I overpass this exception? I need these navigation properties on derived entities, and inheritance seems the only way to provide mapping of 2 entites on the same table with Ef4 CTP5... Any thoughts?

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• Inheritance and type parameters of Traversable

  - by Jesper

  I'm studying the source code of the Scala 2.8 collection classes. I have questions about the hierarchy of scala.collection.Traversable. Look at the following declarations: package scala.collection trait Traversable[+A] extends TraversableLike[A, Traversable[A]] with GenericTraversableTemplate[A, Traversable] trait TraversableLike[+A, +Repr] extends HasNewBuilder[A, Repr] with TraversableOnce[A] package scala.collection.generic trait HasNewBuilder[+A, +Repr] trait GenericTraversableTemplate[+A, +CC[X] <: Traversable[X]] extends HasNewBuilder[A, CC[A] @uncheckedVariance] Question: Why does Traversable extend GenericTraversableTemplate with type parameters [A, Traversable] - why not [A, Traversable[A]]? I tried some experimenting with a small program with the same structure and got a strange error message when I tried to change it to Traversable[A]: error: Traversable[A] takes no type parameters, expected: one I guess that the use of the @uncheckedVariance annotation in GenericTraversableTemplate also has to do with this? (That seems like a kind of potentially unsafe hack to force things to work...). Question: When you look at the hierarchy, you see that Traversable inherits HasNewBuilder twice (once via TraversableLike and once via GenericTraversableTemplate), but with slightly different type parameters. How does this work exactly? Why don't the different type parameters cause an error?

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• In which year was the date the same as the original year?

  - by Marta

  It's my first question on this site, but I always found this site really useful. What I mean with my question is: you ask the person to give a date (eg. Fill in a date [dd-mm-yyyy]: 16-10-2013) you than have to ask an interval between 2 years (eg. Give an interval [yyyy-yyyy]:1800-2000) When the program runs, it has to show what day of the week the given date is. In this case it was a Wednesday. Than the program has to look in which year, in between the interval, the date 16 October also fell on a Wednesday. So in the end it has to look something like this: Fill in a date: [dd-mm-yyyy]: 16-10-2013 Give an interval [yyyy-yyyy]: 1900-2000 16 October was a wednesday in the following years: 1905 1911 1916 1922 1933 1939 1944 1950 1961 1967 1972 1978 1989 1995 2000 The full date is Wednesday 16 October, 2013 The small (or biggest) problem is, I am not allowed to use the DATE.function in java. If someone can help me with the second part I would be really really happy, cause I have no idea how I am supposed to do this To find out what day of the week the given date falls, I use the Zeller Congruence class Day { Date date; //To grab the month and year form the Date class int day; final static String[] DAYS_OF_WEEK = { "Saturday", "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday" }; public void dayWeekInterval{ //code to grab the interval from interval Class, and doing stuff here } public void dayOfTheWeek { int m = date.getMonth(); int y = date.getYear(); if (m < 3) { m += 12; y -= 1; } int k = y % 100; int j = y / 100; int day = ((q + (((m + 1) * 26) / 10) + k + (k / 4) + (j / 4)) + (5 * j)) % 7; return day; } public string ToString(){ return "" + DAYS_OF_WEEK[day] + day; } }

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• Retaining Managed objects - more general retaining objects

  - by Luuk D. Jansen

  A quick question regarding Managed Objects. I created an Array with Managed Objects (in Object 1: TableViewConbtroller), and pass one of those objects to another class/object (object 2: TableCell). The original array should still be retained in the original caller class. Then Object 2 is released, does that mean that that particular item in the array is released as well, as the reference to it in Object 2 was released? I am trying to better understand how to work with ManagedObjects as I get 'Object was released' errors. [EDIT] After some experimenting I came across the following scenario: I have the main AppDelegate. In a different class I create an AppDelegate to obtain the ManagedObjectContext. appDelegate = (iDomsAppDelegate *)[[UIApplication sharedApplication] delegate]; [self setContext:[appDelegate managedObjectContext]]; When the class is finished, and I release it, the variable in the class 'appDelegate' is also released. But then the ManagedObjectContext is closed, and obvious any future attempt to use it will cause a crash. So should I leave the appDelegate unreleased? This comes to the same question as the above about when and how to release in those situations where an objects is used from another class. I think a way of putting it is, how to know when you own an object and when not.

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• WPF ResourceDictionary and DynamicResource

  - by lanicor

  i am new to WPF so maybe this will be "noob" question but i can't find answer to it (and it seems so easy)... well i am programing WPF app and i want to use smth similar to css for webpages, so i found ResourceDictionary and tried to use it... I have main window in which i create Frame and on click some UserControl is loaded to that same Frame.I include my ResourceDictionary (root/style/Styles.xaml) to my main window like this: <Window.Resources> <ResourceDictionary x:Key="styles" Source="style/Styles.xaml" /> </Window.Resources> in which i have: <ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"> <Style x:Key="ProductsRequired" TargetType="{x:Type Label}"> <Setter Property="Height" Value="28" /> ... I don't use it on my main window but want to use it on my UserControls, which are loaded to that main window and i try to use it like this: <Label Name="product1" Style="{DynamicResource ProductsRequired}" /> Warning i am getting all the time is: The resource "ProductsRequired" could not be resolved. I even tried including Styles to my UserControl <UserControl.Resources> <ResourceDictionary x:Key="styles" Source="../style/Styles.xaml" /> </UserControl.Resources> and nothing happens... Well my question is long but i wanted to be clear... :) P.S. all that logic works in C# code btw private ResourceDictionary myStyles = new ResourceDictionary(); Style ProductsRequired = myStyles["ProductsRequired"] as Style; product1.Style = ProductsRequired;

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• What exactly does this PHP code do?

  - by Rob

  Alright, my friend gave me this code for requesting headers and comparing them to what the header should be. It works perfectly, but I'm not sure why. Here is the code: $headers = apache_request_headers(); $customheader = "Header: 7ddb6ffab28bb675215a7d6e31cfc759"; foreach ($headers as $header => $value) { // 1 $custom .= "$header: $value"; // 2 } $mystring = $custom; // 3 $findme = $customheader; // 4 $pos = strpos($mystring, $findme); if ($pos !== false) { // Do something } else{ exit(); } //If it doesn't match, exit. I commented with some numbers relating to the following questions: 1: What exactly is happening here? Is it setting the $headers as $header AND $value? 2: Again, don't have any idea what is going on here. 3: Why set the variable to a different variable? This is the only area where the variable is getting used, so is there a reason to set it to something else? 4: Same question as 3. I'm sorry if this is a terrible question, but its been bothering me, and I really want to know WHY it works. Well, I understand why it works, I guess I just want to know more specifically. Thanks for any insight you can provide.

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• How does the receiver of a cipher text know the IV used for encryption?

  - by PatrickL

  If a random IV is used in encrypting plain text, how does the receiver of the cipher text know what the IV is in order to decrypt it? This is a follow-up question to a response to the previous stackoverflow question on IVs here. The IV allows for plaintext to be encrypted such that the encrypted text is harder to decrypt for an attacker. Each bit of IV you use will double the possibilities of encrypted text from a given plain text. The point is that the attacker doesn't know what the IV is and therefore must compute every possible IV for a given plain text to find the matching cipher text. In this way, the IV acts like a password salt. Most commonly, an IV is used with a chaining cipher (either a stream or block cipher). ... So, if you have a random IV used to encrypt the plain text, how do you decrypt it? Simple. Pass the IV (in plain text) along with your encrypted text. Wait. You just said the IV is randomly generated. Then why pass it as plain text along with the encrypted text?

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• php convert european datetime to mysql datetime

  - by Mathlight

  I'm really stuck with this problem. I've got an datetime string like this: 28-06-14 11:01:00 I'm trying to convert it to 2014-06-28 11:01:00 so that i can insert it into the database ( with field type datetime. I've tryed multiple things like this: $datumHolder = new DateTime($data['datum'], new DateTimeZone('Europe/Amsterdam')); $datum1 = $datumHolder -> format("Y-m-d H:i:s"); $datum2 = date( 'Y-m-d', strtotime(str_replace('-', '/', $data['datum']) ) ); $datum3 = DateTime::createFromFormat( 'Y-m-d-:Hi:s', $data['datum']); This is the output i get: datum1: 2028-06-14 11:01:00 datum2: 1970-01-01 And i get an error for datum3: echo "datum3: " . $datum3->format( 'Y-m-d H:i:s'); . '<br />'; Call to a member function format() on a non-object So my question is very clear... What am I doing wrong / how to get this working? Thanks in advantage guys! I know that this question is asked many, many times... But whatever i try, i can't get it working...

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• Treating differential operator as algebraic entity

  - by chappar

  I know that this question is offtopic and don't belong here. But i didn't know somewhere else to ask. So here is the question. I was reading e:the story of a number by Eli Maor, where he treats differential operator as just like any algebraic entity. For example if we have a differential equation like y’’ + 5y’ - 6y = 0. This can be treaed as (D^2 + 5D – 6)y = 0. So, either y = 0 (trivial solution) or (D^2 + 5D – 6) = 0. Factoring out above equation we get (D-1)(D+6)= 0 with solutions as D = 1 and D = -6. Since D does not have any meaning on its own, multiplying by y on both the sides we get Dy = y and Dy = -6y for which the solutions are Ae^x and Be^-6x. Combining these 2 solutions we get Ae^x + Be^-6x. Now my doubt is this approach break when we have an equation like D^2y = 0. Which means y = 0 (again trivial) or D^2 = 0 which means D = 0. Now Dy = y*0 = 0. That means y = C ( a constant). The actual answer should be Cx. I know that it is stupidity to treat D^2 = 0 as D = 0, it led me to doubt the entire process of treating differential equation as algebraic equation. Can someone throw light on this? Or any other site where i might get answer?

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• Make TBODY scrollable in Webkit browsers

  - by Andrew

  I'm aware of this question, but none of the answers work in Safari, Chrome, etc. The accepted strategy (as demonstrated here) is to set the tbody height and overflow properties like so: <table> <thead> <tr><th>This is the header and doesn't scroll</th></tr> </thead> <tbody style="height:100px; overflow:auto;"> <tr><td>content that scrolls</td></tr> <tr><td>content that scrolls</td></tr> <tr><td>content that scrolls</td></tr> <tr><td>content that scrolls</td></tr> <tr><td>content that scrolls</td></tr> <tr><td>content that scrolls</td></tr> <tr><td>content that scrolls</td></tr> </tbody> </table> Unfortunately, this does not work in any webkit browsers. There is a bug report about it that doesn't seem to be a high priority (reported June 05). So my question is: are there alternate strategies that do actually work? I've tried the two-table approach, but it's impossible to guarantee that the header will line up with the content. Do I just have to wait for Webkit to fix it?

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• problem configure JBoss to work with JNDI(2)

  - by Spiderman

  in continuation to the question from last week: http://stackoverflow.com/questions/2828237/problem-configure-jboss-to-work-with-jndi I'm trying to bind datasource in JBoss and use it in my application. In my struggling, I already managed to avoid the javax.naming.NameNotFoundException by: 1. using in java new InitialContext().lookup(connection); instead of new JndiObjectFactoryBean().setJndiName(connection); 2. changing the connection name from: 'jndi-name' to 'java:jndi-name' Now the problem is that the datasouce that I get from the lookup is null. I created the datsource file: <datasources> <local-tx-datasource> <jndi-name>bilby</jndi-name> <connection-url>jdbc:oracle:myURL</connection-url> <driver-class>oracle.jdbc.OracleDriver </driver-class> <user-name>myUsername</user-name> <password>myPassword</password> <exception-sorter-class- name>org.jboss.resource.adapter.jdbc.vendor.OracleExceptionSorter</exception-sorter-class-name> <metadata> <type-mapping>Oracle9i</type-mapping> </metadata> </local-tx-datasource> </datasources> and put it under \server\default\deploy\oracle-ds.xml I get during runtime the line: 18:37:56,560 INFO [ConnectionFactoryBindingService] Bound ConnectionManager 'jb oss.jca:service=DataSourceBinding,name=bilby' to JNDI name 'java:bilby' So my question is - why do I get null as my datasource???

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• I want just the insert query for a temp table.

  - by John Stephen

  Hi..I am using C#.Net and Sql Server ( Windows Application ). I had created a temporary table. When a button is clicked, temporary table (#tmp_emp_details) is created. I am having another button called "insert Values" and also 5 textboxes. The values that are entered in the textbox are used and whenever com.ExecuteNonQuery(); line comes, it throws an error message Invalid object name '#tbl_emp_answer'.. Below is the set of code.. Please give me a solution. Code for insert (in insert value button): private void btninsertvalues_Click(object sender, EventArgs e) { username = txtusername.Text; examloginid = txtexamloginid.Text; question = txtquestion.Text; answer = txtanswer.Text; useranswer = txtanswer.Text; SqlConnection con = new SqlConnection("Data Source=.;Initial Catalog=tempdb;Integrated Security=True;"); SqlCommand com = new SqlCommand("Insert into #tbl_emp_answer values('"+username+"','"+examloginid+"','"+question+"','"+answer+"','"+useranswer+"')", con); con.Open(); com.ExecuteNonQuery(); con.Close(); }

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• Is it possible to spoof or reuse VIEWSTATE or detect if it is protected from modification?

  - by Peter Jaric

  Question ASP and ASP.NET web applications use a value called VIEWSTATE in forms. From what I understand, this is used to persist some kind of state on the client between requests to the web server. I have never worked with ASP or ASP.NET and need some help with two questions (and some sub-questions): 1) Is it possible to programmatically spoof/construct a VIEWSTATE for a form? Clarification: can a program look at a form and from that construct the contents of the base64-encoded VIEWSTATE value? 1 a) Or can it always just be left out? 1 b) Can an old VIEWSTATE for a particular form be reused in a later invocation of the same form, or would it just be luck if that worked? 2) I gather from http://msdn.microsoft.com/en-us/library/ms972976.aspx#viewstate_topic12 that it is possible to turn on security so that the VIEWSTATE becomes secure from spoofing. Is it possible for a program to detect that a VIEWSTATE is safeguarded in such a way? 2 a) Is there a one-to-one mapping between the occurrence of EVENTVALIDATION values and secure VIEWSTATEs? Regarding 1) and 2), if yes, can I have a hint about how I would do that? For 2) I am thinking I could base64-decode the value and search for a string that always is found in unencrypted VIEWSTATEs. "First:"? Something else? Background I have made a small tool for detecting and exploiting so called CSRF vulnerabilities. I use it to quickly make proof of concepts of such vulnerabilities that I send to the affected site owners. Quite often I encounter these forms with a VIEWSTATE, and these I don't know if they are secure or not. Edit 1: Clarified question 1 somewhat. Edit 2: Added text in italics.

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• Chrome renders button links completely screwed up when placed inside a paragraph

  - by Ferdy

  I am fairly proficient in CSS but now I am running into a very strange rendering issue in Google Chrome 9. I am trying to create some fancy looking link buttons (basically heavily styled anchors). Here is some example markup: <a href="" class="button"> <figure class="sprite icon icon_back"></figure> Link button with icon</a> This markup may look a litte strange to you, there's a few things you should know: I am using HTML5's figure class to include an icon as part of the button. I have the proper reset CSS applied and Chrome can render this tag for sure. Instead of actually pointing to an image I am applying CSS classes to the figure element. Within the CSS I am using the spriting technique to show the correct portion of a single large sprite image. All of this is working fine in Firefox, and actually also in Chrome. The correct rendering can be seen in the following image: It renders like that in both Firefox and Chrome. Here comes the problem, if I place such a button within paragraph tags <p></p> this is what happens in Chrome only: Notice how the button is ripped apart? Only in Chrome and only when placed inside a paragraph. It gets even stranger: this only happens for the first button inside the paragraph, if I would place three buttons inside a paragraph, only the 1st one is screwed up. Your first question would probably be about the CSS. It is rather verbose so hereby a temporary link to the page in question: Edit: link to live page removed, was only temporary for problem inspection.

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• Trailing comments after variable assignment subvert comparison

  - by nobar

  In GNU make, trailing comments appended to variable assignments prevent subsequent comparison (via ifeq) from working correctly. Here's the Makefile... A = a B = b ## trailing comment C = c RESULT := ifeq "$(A)" "a" RESULT += a endif ifeq "$(B)" "b" RESULT += b endif ifeq "$(C)" "c" RESULT += c endif rule: @echo RESULT=\"$(RESULT)\" @echo A=\"$(A)\" @echo B=\"$(B)\" @echo C=\"$(C)\" Here's the output... $ make RESULT=" a c" A="a" B="b " C="c" As you can see from the displayed value of RESULT, the ifeq was affected by the presence of the comment in the assignment of B. Echoing the variable B, shows that the problem is not the comment, but the intervening space. The obvious solution is to explicitly strip the whitespace prior to comparison like so... ifeq "$(strip $(B))" "b" RESULT += b endif However this seems error prone. Since the strip operation is not needed unless/until a comment is used, you can leave out the strip and everything will initially work just fine -- so chances are you won't always remember to add the strip. Later, if someone adds a comment when setting the variable, the Makefile no longer works as expected. Note: There is a closely related issue, as demonstrated in this question, that trailing whitespace can break string compares even if there is no comment. Question: Is there a more fool-proof way to deal with this issue?

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• Java Enumeration of Musical Notes

  - by Crupler

  How would you create an enumeration of the musical notes in Java, with each notes having an octave and then a keyed variable? This is what I have so far... public enum Notes { c, cS, d, dS, e, f, fS, g, gS, a, aS, b; int octave; boolean isPlaying; } So when I access the enums in my code I write something like this... Notes.c.octave = 4; Notes.c.isPlaying = true; Now here is my question: How can I have an isPlaying boolean for each note in each octave? Like so: Notes.c.octave.isPlaying = true; Or would I have to go like: public enum Notes { c1, cS1, d1, dS1, e1, f1, fS1, g1, gS1, a1, aS1, b1 c2, cS2, d2, dS2, e2, f2, fS2, g2, gS2, a2, aS2, b2; etc... boolean isPlaying; } Thank you in advance for taking your time to answer this question!

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• Why won't WPF databindings show text when ToString() has a collaborating object?

  - by Jay

  In a simple form, I bind to a number of different objects -- some go in listboxes; some in textblocks. A couple of these objects have collaborating objects upon which the ToString() method calls when doing its work -- typically a formatter of some kind. When I step through the code I see that when the databinding is being set up, ToString() is called the collaborating object is not null and returns the expected result when inspected in the debugger, the objects return the expected result from ToString() BUT the text does not show up in the form. The only common thread I see is that these use a collaborating object, whereas the other bindings that show up as expected simply work from properties and methods of the containing object. If this is confusing, here is the gist in code: public class ThisThingWorks { private SomeObject some_object; public ThisThingWorks(SomeObject s) { some_object = s; } public override string ToString() { return some_object.name; } } public class ThisDoesntWork { private Formatter formatter; private SomeObject some_object; public ThisDoesntWork(SomeObject o, Formatter f) { formatter = f; some_object = o; } public override string ToString() { return formatter.Format(some_object.name); } } Again, let me reiterate -- the ToString() method works in every other context -- but when I bind to the object in WPF and expect it to display the result of ToString(), I get nothing. Update: The issue seems to be what I see as a buggy behaviour in the TextBlock binding. If I bind the Text property to a property of the DataContext that is declared as an interface type, ToString() is never called. If I change the property declaration to an implementation of the interface, it works as expected. Other controls, like Label work fine when binding the Content property to a DataContext property declared as either the implementation or the interface. Because this is so far removed from the title and content of this question, I've created a new question here: http://stackoverflow.com/questions/2917878/why-doesnt-textblock-databinding-call-tostring-on-a-property-whose-compile-tim

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• How can I create global context variables in JBOSS?

  - by NobodyMan

  This is a follow-up to a question I posted a while back: "Can I use a single WAR in multiple environments?". I was able to create a single-war solution in Tomcat, but now we are migrating our app to JBoss 4.2 and I can't figure out how to set up global environment variables. In Tomcat 6 this was pretty straightforward: I simply put the following snippet in tomcat/conf/Catalina/myappname.xml: <Context ...> <Environment name="TARGET_ENV" value="DEV" type="java.lang.String" override="false"/> </Context> Then in my app I was able to resolve the environment name with the following: Context context = (Context) InitialContext().lookup("java:comp/env"); String targetEnvironment = (String) context.lookup("TARGET_ENV"); The problem is that I can't find out where/how to place global variables in JBoss. I've tried putting the <Environment> tag in the following files to no avail: server/all/deploy/jboss-web.deployer/context.xml server/default/deploy/jboss-web.deployer/context.xml I know that I can put environment variables in my app's web.xml but that defeats the purpose of having a unified war - I'd still need custom .war's for dev, qa and prod. I'm a JBoss newbie so if there's any additional information that would help just let me know and I'll append to this question. Many thanks! --N

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• Partial class or "chained inheritance"

  - by Charlie boy

  Hi From my understanding partial classes are a bit frowned upon by professional developers, but I've come over a bit of an issue; I have made an implementation of the RichTextBox control that uses user32.dll calls for faster editing of large texts. That results in quite a bit of code. Then I added spellchecking capabilities to the control, this was made in another class inheriting RichTextBox control as well. That also makes up a bit of code. These two functionalities are quite separate but I would like them to be merged so that I can drop one control on my form that has both fast editing capabilities and spellchecking built in. I feel that simply adding the code form one class to the other would result in a too large code file, especially since there are two very distinct areas of functionality, so I seem to need another approach. Now to my question; To merge these two classes should I make the spellchecking RichTextBox inherit from the fast edit one, that in turn inherits RichTextBox? Or should I make the two classes partials of a single class and thus making them more “equal” so to speak? This is more of a question of OO principles and exercise on my part than me trying to reinvent the wheel, I know there are plenty of good text editing controls out there. But this is just a hobby for me and I just want to know how this kind of solution would be managed by a professional. Thanks!

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• WHY JSLint complains: "someFunction() was used before it was defined"?

  - by 7hi4g0

  Searching for the JSLint error "was used before it was defined" i've found these: JSLint: Using a function before it's defined error Function was used before it was defined - JSLint JSLint: was used before it was defined jsLint error: “somefunction() was used before it was defined” jslint - Should we tolerate misordered definitions? Problem None of those answers WHY the error is shown. Elaboration According to the ECMA-262 Specification functions are evaluated before execution starts, hence all functions declared using the function keyword are available to all the code idenpendent of the place they were declared (assuming they are acessible on that scope). This is otherwise known as hoisting. Douglas Crockford seems to think it is better to declare every function before the code that uses it regardless of the hoisting effect. According to StackOverflowNewbie in his question, this raises some code organization problems. Not to mention some people, like me, prefer to declare their functions underneath the main/init code. On those questions there are some ways to avoid or fix the error, such as using function expressions vs function declarations. But none of them showed me the reason of the error. Not even Crockford's site. Question(s) Why is it an error to call a function before the declaration, even if it was declared using the function keyword? Is it better to use function expressions instead of function declaration in the JSLint context? If one is preferred, why? Note Not looking for answers like: Crockford is a tyrant Is just Crockford's opinion Thank you :*

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• Request for advice about class design, inheritance/aggregation

  - by Lasse V. Karlsen

  I have started writing my own WebDAV server class in .NET, and the first class I'm starting with is a WebDAVListener class, modelled after how the HttpListener class works. Since I don't want to reimplement the core http protocol handling, I will use HttpListener for all its worth, and thus I have a question. What would the suggested way be to handle this: Implement all the methods and properties found inside HttpListener, just changing the class types where it matters (ie. the GetContext + EndGetContext methods would return a different class for WebDAV contexts), and storing and using a HttpListener object internally Construct WebDAVListener by passing it a HttpListener class to use? Create a wrapper for HttpListener with an interface, and constrct WebDAVListener by passing it an object implementing this interface? If going the route of passing a HttpListener (disguised or otherwise) to the WebDAVListener, would you expose the underlying listener object through a property, or would you expect the program that used the class to keep a reference to the underlying HttpListener? Also, in this case, would you expose some of the methods of HttpListener through the WebDAVListener, like Start and Stop, or would you again expect the program that used it to keep the HttpListener reference around for all those things? My initial reaction tells me that I want a combination. For one thing, I would like my WebDAVListener class to look like a complete implementation, hiding the fact that there is a HttpListener object beneath it. On the other hand, I would like to build unit-tests without actually spinning up a networked server, so some kind of mocking ability would be nice to have as well, which suggests I would like the interface-wrapper way. One way I could solve this would be this: public WebDAVListener() : WebDAVListener(new HttpListenerWrapper()) { } public WebDAVListener(IHttpListenerWrapper listener) { } And then I would implement all the methods of HttpListener (at least all those that makes sense) in my own class, by mostly just chaining the call to the underlying HttpListener object. What do you think? Final question: If I go the way of the interface, assuming the interface maps 1-to-1 onto the HttpListener class, and written just to add support for mocking, is such an interface called a wrapper or an adapter?

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