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• stackoverflow tags and related tags

  - by parminder

  Hi Experts, I am working on a website where a user can add tags to their posted books. It is similar to stackover flow, but I am keeping my tags in differnt table. so here are the tables/class in linq to entities. Books { bookId, Title } Tags { Id Tag } BooksTags { Id BookId TagId } Here are few sample records. Books BookId Title 113421 A 113422 B Tags Id Tag 1 ASP 2 C# 3 CSS 4 VB 5 VB.NET 6 PHP 7 java 8 pascal BooksTags Id BookId TagId 1 113421 1 2 113421 2 3 113421 3 4 113421 4 5 113422 1 6 113422 4 7 113422 8 Question 1 : I need to write something in linq to entities queries which gives me data according to the tags say if I want bookIds where tagid =1 it should return bookid 113421 and 113422 as it exists in both the books, but If I ask data for tags 1 and 2 it should return only book 113421 as that is the only book where both the tags are present. Question 2 : I need tags and their count too to show in related tags, so in first case my related tags class should have following result. RelatedTags Tag Count 2 1 3 1 4 2 8 1 in the second case when two tags are requested the result should be like RelatedTags Tag Count 3 1 4 1 I have get the first thing working by converting a sql query in linqer, but that seems like a hell. so want to know if there is any better idea. I have used dyanmic where clause to include two tags. So if someone can help. It will be much appreciated. Thanks Parminder

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• Using Reachability for Internet *or* local WiFi?

  - by randallmeadows

  I've searched SO for the answer to this question, and it's not really addressed, at least not to a point where I can make it work. I was originally only checking for Internet reachability, using: self.wwanReach = [Reachability reachabilityWithHostName:@"www.apple.com"]; [wwanReach startNotifer]; I now need to support a local WiFi connection (in the absence of reaching the Internet in general), and when I found +reachabilityForLocalWiFi, I also noticed there was +reachabilityForInternetConnection. I figured I could use these, instead of hard-coding "www.apple.com" in there, but alas, when I use self.wwanReach = [Reachability reachabilityForInternetConnection]; [wwanReach startNotifer]; self.wifiReach = [Reachability reachabilityForLocalWiFi]; [wifiReach startNotifer]; the reachability callback that I've set up "never" gets called, for values of "never" up to 10, 12, 15 minutes or so (which was as long as my patience lasted. (User's patience will be much less, I'm sure.) Switching back to +reachabilityWithHostName: works within seconds. I also tried each "pair" individually, in case there was an issue with two notifiers in progress simultaneously, but that made no difference. So: what is the appropriate way to determine reachability to either the Internet/WWAN or a local Wifi network (either one, or both)? [This particular use case is an iPhone or iPad connecting to a Mac mini computer-to-computer network; I'm sure other situations apply.]

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• Is it possible to replace values ina queryset before sending it to your template?

  - by Issy

  Hi Guys, Wondering if it's possible to change a value returned from a queryset before sending it off to the template. Say for example you have a bunch of records Date | Time | Description 10/05/2010 | 13:30 | Testing... etc... However, based on the day of the week the time may change. However this is static. For example on a monday the time is ALWAYS 15:00. Now you could add another table to configure special cases but to me it seems overkill, as this is a rule. How would you replace that value before sending it to the template? I thought about using the new if tags (if day=1), but this is more of business logic rather then presentation. Tested this in a custom template tag def render(self, context): result = self.model._default_manager.filter(from_date__lte=self.now).filter(to_date__gte=self.now) if self.day == 4: result = result.exclude(type__exact=2).order_by('time') else: result = result.order_by('type') result[0].time = '23:23:23' context[self.varname] = result return '' However it still displays the results from the DB, is this some how related to 'lazy' evaluation of templates? Thanks! Update Responding to comments below: It's not stored wrong in the DB, its stored Correctly However there is a small side case where the value needs to change. So for example I have a From Date & To date, my query checks if todays date is between those. Now with this they could setup a from date - to date for an entire year, and the special cases (like mondays as an example) is taken care off. However if you want to store in the DB you would have to capture several more records to cater for the side case. I.e you would be capturing the same information just to cater for that 1 day when the time changes. (And the time always changes on the same day, and is always the same)

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• Generated HTML word document not displaying image correctly

  - by spiderdijon

  I'm trying to add an image to a generated html word document that is embedded in a classic ASP page. The code looks something like this: <% Response.ContentType = "application/msword" %> <html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word"> ... <v:shape id="_x0000_s1030" type="#_x0000_t75" style='position:absolute; left:0;text-align:left;margin-left:0;margin-top:17.95pt;width:7in;height:116.85pt; z-index:2;mso-position-horizontal:center;mso-position-horizontal-relative:page; mso-position-vertical-relative:page'> <v:imagedata src="http://xxx/image001.gif" o:title="image001"/> <w:wrap anchorx="page" anchory="page"/> <w:anchorlock/> </v:shape><![endif]--><![if !vml]><span style='mso-ignore:vglayout;position: absolute;z-index:0;left:0px;margin-left:0px;margin-top:24px;width:672px; height:156px'><img width=672 height=156 src="http://xxx/image001.gif" v:shapes="_x0000_s1030"></span><![endif]> The image URL is correct and can be viewed through a browser, however when the word document opens, the image has a red x, with the error message: The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may be corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again. If i copy the html code and try to open the word document on my local machine, it displays the image correctly. It just doesn't work when retrieving the document from the server. This happens for any images I try to add. Is there another way to add images to html-generated word documents that can be output from an asp page? Thanks.

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• trouble finding element on page using xpath or css

  - by doneright

  Guys, I'm trying to write xpath or css to find/click on list element "All" based on known span(in this case SNG NAME below). On page, there are different lists Which can contain same list item called as "All". So we have to identify "All" based on span(in this case SNG NAME below) can someone shed some light on my issue <html> <head> <body> <div class="grc_selected"> <div class ="lbl_selected"> <span> SNG NAME </span> </div> <div id="id1" class="cl1"> <ul id="id_ul"> <li class="tclass" title="[1] All"> <img class="treeIcon" src="1/2/3.gif"/> <span class="inA">All</span> </li> </ul> </div> </body> </head> </html>

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• Process-to-port mapping with SNMP and/or wmi/wmic in java

  - by Niddy888

  I'm trying to use SNMP to map outgoing ports on my host computer with the application running on the computer that is responsible for that communication. When running "netstat -ano" I get access to Protocol, Local Address (with port), Foreign Address (with port), State and PID. But I want to do this entirely without having to execute "cmd" from Java. By using SNMP OID: .1.3.6.1.2.1.25.4 (.iso.org.dod.internet.mgmt.mib-2.host.hrSWRun) I get access to PID (ex. 1704), Name (ex. cmd.exe), Path (ex. C:\Windows\system32) among others. There is an SNMP OID: .1.3.6.1.2.1.6.13 (.iso.org.dod.internet.mgmt.mib-2.tcp.tcpConnTable) that give you access to TCP connection state, local address, local port, remote address, remote port. But NO PID. So to sum up. My question again: Is there a way to "map" these tables together? Either directly in SNMP with other OID's or in conjunction with WMI / WMIC?

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• Determine the folder of a SAS source file

  - by exhuma

  When I open a SAS file in enterprise guide and run it, it is executed on the server. The source file itself is located either on the production site or the development site. In both cases, it is executed the same server however. I want to be able to tell my script to store results in a relative folder. But if I write something like libname lib_out xport "..\tmp\foobar.xpt"; I get an error, because the working folder of the SAS Enterprise Guide process is not the location of my source file, but a folder on the server. And the folder ..\tmp does not exist there. Even if it would, the server process does not have write permission in that folder. I would like to determine from which folder the .sas file was loaded and set the working folder accordingly. In one case it's S:\Development\myproject\sas\foobar.sas and in the other case it's S:\Production\myproject\sas\foobar.sas It this possible at all? Or how would you do this?

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• Using a Context Menu to delete from a SQLite database in Android

  - by LordSnoutimus

  Hi, I have created a list view that displays the names and dates of items stored in a SQLite database, now I want to use a Context Menu to modify these items stored in the database such as edit the name, delete, and view. This is the code for the list view: public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.listview); SQLiteDatabase myDB = null; myDB = this.openOrCreateDatabase(MY_DB_NAME, MODE_PRIVATE, null); Cursor cur = myDB.rawQuery("SELECT _id, trackname, tracktime" + " FROM " + MY_DB_TABLE, null); ListAdapter adapter = new SimpleCursorAdapter(this, R.layout.listview, cur, new String[] { Constants.TRACK_NAME, Constants.TRACK_TIME}, new int[] { R.id.text1, R.id.text2}); ListView list = (ListView)findViewById(R.id.list); list.setAdapter(adapter); registerForContextMenu(list); } and the Context Menu... public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo) { super.onCreateContextMenu(menu, v, menuInfo); menu.setHeaderTitle("Track Options"); menu.add(0, CHANGE_NAME, 0, "Change name"); menu.add(0, VIEW_TRACK, 0, "View track"); menu.add(0, SEND_TRACK, 0, "Send track"); menu.add(0, DELETE_TRACK, 0, "Delete track"); } I have used a Switch statement to control the menu items.. public boolean onContextItemSelected(MenuItem item) { switch (item.getItemId()){ case CHANGE_NAME: changename(); return true; case DELETE_TRACK: deletetrack(); return true; default: return super.onContextItemSelected(item); } So how would I go ahead and map the deletetrack(); method to find the ID of the track stored in the database to the item that has been selected in the list view?

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• echo -e acts differently when run in a script by root on ubuntu

  - by ekrub

  When running a bash script on ubuntu 9.10, I get different behavior from bash echo's "-e" option depending on whether or not I'm running as root. Consider this script: $ cat echo-test if [ "`whoami`" = "root" ]; then echo "Running as root" fi echo Testing /bin/echo -e /bin/echo -e "foo\nbar" echo Testing bash echo -e echo -e "foo\nbar" When run as non-root user, I see this output: $ ./echo-test Testing /bin/echo -e foo bar Testing bash echo -e foo bar When run as root, I see this output: $ sudo ./echo-test Running as root Testing /bin/echo -e foo bar Testing bash echo -e -e foo bar Notice the "-e" being echoed in the last case ("-e foo" instead of "foo" on the second-to-last line). When running a script as root, the echo command runs as if "-e" was given and, if -e is given, the option itself is echoed. I can understand some subtle differences in behavior between /bin/echo and bash echo, but I would expect bash echo to behave the same no matter which user invokes it. Anyone know why this is the case? Is this a bug in bash echo? FYI -- I'm running GNU bash, version 4.0.33(1)-release (x86_64-pc-linux-gnu)

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• Why can't I roll a loop in Javascript?

  - by Carl Manaster

  I am working on a web page that uses dojo and has a number (6 in my test case, but variable in general) of project widgets on it. I'm invoking dojo.addOnLoad(init), and in my init() function I have these lines: dojo.connect(dijit.byId("project" + 0).InputNode, "onChange", function() {makeMatch(0);}); dojo.connect(dijit.byId("project" + 1).InputNode, "onChange", function() {makeMatch(1);}); dojo.connect(dijit.byId("project" + 2).InputNode, "onChange", function() {makeMatch(2);}); dojo.connect(dijit.byId("project" + 3).InputNode, "onChange", function() {makeMatch(3);}); dojo.connect(dijit.byId("project" + 4).InputNode, "onChange", function() {makeMatch(4);}); dojo.connect(dijit.byId("project" + 5).InputNode, "onChange", function() {makeMatch(5);}); and change events for my project widgets properly invoke the makeMatch function. But if I replace them with a loop: for (var i = 0; i < 6; i++) dojo.connect(dijit.byId("project" + i).InputNode, "onChange", function() {makeMatch(i);}); same makeMatch() function, same init() invocation, same everything else - just rolling my calls up into a loop - the makeMatch function is never called; the objects are not wired. What's going on, and how do I fix it? I've tried using dojo.query, but its behavior is the same as the for loop case.

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• Hibernate not saving foreign key, but with junit it's ok

  - by Leonardo

  Hi All, I have this strange problem. In a J2ee webapp with spring, smartgwt and hibernate, it happens that I have a class A wich has a set of class B, both of them mapped to table A and table B. I wrote a simple test case for testing the service manager which is supposed to do insert, update, delete and everything work as expected especially during insert. In the end I have one record in A and records in B with foreign key to A. But when I try to call the service from the web app, the entity in B are saved without a foreign key reference. I am sure that the service is the same. One thing I noticed is that enabling hibernate logging, seems that when the service is called from the application, one more update is made: insert A insert B update A update B update B (foreign key only) update A <--- ??? update B <--- ??? Instead, when junit test case is run, the update is as follows: insert A insert B update A update B update B (foreign key only) I suppose the latest update is what is causing the erroe, maybe it is overwriting values. Considering that the app is using spring, with the well known mechanism of DAO + Manager, where can I investigate to solve this issue ? Someone told me that the session is not closed, so hibernate would do one more update before release the objects by itself. I am pretty sure that all the configuration hbm, xml, and the rest are fine...but I maybe wrong. thanks

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• Interchange structured data between Haskell and C

  - by Eonil

  First, I'm a Haskell beginner. I'm planning integrating Haskell into C for realtime game. Haskell does logic, C does rendering. To do this, I have to pass huge complexly structured data (game state) from/to each other for each tick (at least 30 times per second). So the passing data should be lightweight. This state data may laid on sequential space on memory. Both of Haskell and C parts should access every area of the states freely. In best case, the cost of passing data can be copying a pointer to a memory. In worst case, copying whole data with conversion. I'm reading Haskell's FFI(http://www.haskell.org/haskellwiki/FFICookBook#Working_with_structs) The Haskell code look specifying memory layout explicitly. I have a few questions. Can Haskell specify memory layout explicitly? (to be matched exactly with C struct) Is this real memory layout? Or any kind of conversion required? (performance penalty) If Q#2 is true, Any performance penalty when the memory layout specified explicitly? What's the syntax #{alignment foo}? Where can I find the document about this? If I want to pass huge data with best performance, how should I do that? *PS Explicit memory layout feature which I said is just C#'s [StructLayout] attribute. Which is specifying in-memory position and size explicitly. http://www.developerfusion.com/article/84519/mastering-structs-in-c/ I'm not sure Haskell has matching linguistic construct matching with fields of C struct.

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• Linq to Entities custom ordering via position mapping table

  - by Bigfellahull

  Hi, I have a news table and I would like to implement custom ordering. I have done this before via a positional mapping table which has newsIds and a position. I then LEFT OUTER JOIN the position table ON news.newsId = position.itemId with a select case statement CASE WHEN [position] IS NULL THEN 9999 ELSE [position] END and order by position asc, articleDate desc. Now I am trying to do the same with Linq to Entities. I have set up my tables with a PK, FK relationship so that my News object has an Entity Collection of positions. Now comes the bit I can't work out. How to implement the LEFT OUTER JOIN. I have so far: var query = SelectMany (n => n.Positions, (n, s) => new { n, s }) .OrderBy(x => x.s.position) .ThenByDescending(x => x.n.articleDate) .Select(x => x.n); This kinda works. However this uses a INNER JOIN so not what I am after. I had another idea: ret = ret.OrderBy(n => n.ShufflePositions.Select(s => s.position)); However I get the error DbSortClause expressions must have a type that is order comparable. I also tried ret = ret.GroupJoin(tse.ShufflePositions, n => n.id, s => s.itemId, (n, s) => new { n, s }) .OrderBy(x => x.s.Select(z => z.position)) .ThenByDescending(x => x.n.articleDate) .Select(x => x.n); but I get the same error! If anyone can help me out, it would be much appreciated!

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• Few Basic Questions in Overriding

  - by Dahlia

  I have few problems with my basic and would be thankful if someone can clear this. What does it mean when I say base *b = new derived; Why would one go for this? We very well separately can create objects for class base and class derived and then call the functions accordingly. I know that this base *b = new derived; is called as Object Slicing but why and when would one go for this? I know why it is not advisable to convert the base class object to derived class object (because base class is not aware of the derived class members and methods). I even read in other StackOverflow threads that if this is gonna be the case then we have to change/re-visit our design. I understand all that, however, I am just curious, Is there any way to do this? class base { public: void f(){cout << "In Base";} }; class derived:public base { public: void f(){cout << "In Derived";} }; int _tmain(int argc, _TCHAR* argv[]) { base b1, b2; derived d1, d2; b2 = d1; d2 = reinterpret_cast<derived*>(b1); //gives error C2440 b1.f(); // Prints In Base d1.f(); // Prints In Derived b2.f(); // Prints In Base d1.base::f(); //Prints In Base d2.f(); getch(); return 0; } In case of my above example, is there any way I could call the base class f() using derived class object? I used d1.base()::f() I just want to know if there any way without using scope resolution operator? Thanks a lot for your time in helping me out!

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• How to write this function as a pL/pgSQl function ?

  - by morpheous

  I am trying to implement some business logic in a PL/pgSQL function. I have hacked together some pseudo code that explains the type of business logic I want to include in the function. Note: This function returns a table, so I can use it in a query like: SELECT A.col1, B.col1 FROM (SELECT * from some_table_returning_func(1, 1, 2, 3)) as A, tbl2 as B; The pseudocode of the pl/PgSQL function is below: CREATE FUNCTION some_table_returning_func(uid int, type_id int, filter_type_id int, filter_id int) RETURNS TABLE AS $$ DECLARE where_clause text := 'tbl1.id = ' + uid; ret TABLE; BEGIN switch (filter_type_id) { case 1: switch (filter_id) { case 1: where_clause += ' AND tbl1.item_id = tbl2.id AND tbl2.type_id = filter_id'; break; //other cases follow ... } break; //other cases follow ... } // where clause has been built, now run query based on the type ret = SELECT [COL1, ... COLN] WHERE where_clause; IF (type_id <> 1) THEN return ret; ELSE return select * from another_table_returning_func(ret,123); ENDIF; END; $$ LANGUAGE plpgsql; I have the following questions: How can I write the function correctly to (i.e. EXECUTE the query with the generated WHERE clause, and to return a table How can I write a PL/pgSQL function that accepts a table and an integer and returns a table (another_table_returning_func) ?

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• Error in Ordinary Differential Equation representation

  - by Priya M

  UPDATE I am trying to find the Lyapunov Exponents given in link LE. I am trying to figure it out and understand it by taking the following eqs for my case. These are a set of ordinary differential equations (these are just for testing how to work with cos and sin as ODE) f(1)=ALPHA*(y-x); f(2)=x*(R-z)-y; f(3) = 10*cos(x); and x=X(1); y=X(2); cos(y)=X(3); f1 means dx/dt;f2 dy/dt and f3 in this case would be -10sinx. However,when expressing as x=X(1);y=X(2);i am unsure how to express for cos.This is just a trial example i was doing so as to know how to work with equations where we have a cos,sin etc terms as a function of another variable. When using ode45 to solve these Eqs [T,Res]=sol(3,@test_eq,@ode45,0,0.01,20,[7 2 100 ],10); it throws the following error ??? Attempted to access (2); index must be a positive integer or logical. Error in ==> Eq at 19 x=X(1); y=X(2); cos(x)=X(3); Is my representation x=X(1); y=X(2); cos(y)=X(3); alright? How to resolve the error? Thank you

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• Chrome extension sendRequest from async callback not working?

  - by Eugene

  Can't figure out what's wrong. onRequest not triggered on call from async callback method, the same request from content script works. The sample code below. background.js ============= ... makeAsyncRequest(); ... chrome.extension.onRequest.addListener(function(request, sender, sendResponse) { switch (request.id) { case "from_content_script": // This works console.log("from_content_script"); sendResponse({}); // clean up break; case "from_async": // Not working! console.log("from_async"); sendResponse({}); // clean up break; } }); methods.js ========== makeAsyncRequest = function() { ... var xhr = new XMLHttpRequest(); xhr.onreadystatechange = function() { if (xhr.readyState == 4) { ... // It works console.log("makeAsyncRequest callback"); chrome.extension.sendRequest({id: "from_async"}, function(response) { }); } } ... }; UPDATE: manifest configuration file. Don't no what's wrong here. { "name": "TestExt", "version": "0.0.1", "icons": { "48": "img/icon-48-green.gif" }, "description": "write it later", "background_page": "background.html", "options_page": "options.html", "browser_action": { "default_title": "TestExt", "default_icon": "img/icon-48-green.gif" }, "permissions": [ "tabs", "http://*/*", "https://*/*", "file://*/*", "webNavigation" ] }

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• How to implement jsf validator?

  - by Krishna

  HI, I want to know how to implement Validator in JSF. What is the advantages of declaring the validator-id. When it will be called in the life cycle?. I have implemented the following code. Please find out what is wrong in the code. I am not seeing it called anywhere in the life cycle. <?xml version="1.0"?> <!DOCTYPE faces-config PUBLIC "-//Sun Microsystems, Inc.//DTD JavaServer Faces Config 1.1//EN" "http://java.sun.com/dtd/web-facesconfig_1_1.dtd"> <faces-config> <lifecycle> <phase-listener>javabeat.net.jsf.JsfPhaseListener</phase-listener> </lifecycle> <validator> <validator-id>JsfValidator</validator-id> <validator-class>javabeat.net.jsf.JsfValidator</validator-class> </validator> <managed-bean> <managed-bean-name>jsfBean</managed-bean-name> <managed-bean-class>javabeat.net.beans.ManagedBean</managed-bean-class> <managed-bean-scope>request</managed-bean-scope> </managed-bean> <navigation-rule> <navigation-case> <from-outcome>success</from-outcome> <to-view-id>success.jsp</to-view-id> </navigation-case> </navigation-rule> </faces-config> public class JsfValidator implements Validator { public JsfValidator() { System.out.println("Inside JsfValidator Constructor"); } @Override public void validate(FacesContext facesContext, UIComponent uiComponent, Object object) throws ValidatorException { System.out.println("Inside Validator"); } }

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• Javascript/jQuery: programmatically follow a link

  - by Dan

  In Javascript code, I would like to programmatically cause the browser to follow a link that's on my page. Simple case: <a id="foo" href="mailto:[email protected]">something</a> function goToBar() { $('#foo').trigger('follow'); } This is hypothetical as it doesn't actually work. And no, triggering click doesn't do it. I am aware of window.location and window.open but these differ from native link-following in some ways that matter to me: a) in the presence of a <base /> element, and b) in the case of mailto URLs. The latter in particular is significant. In Firefox at least, calling window.location.href = "mailto:[email protected]" causes the window's unload handlers to fire, whereas simply clicking a mailto link does not, as far as I can tell. I'm looking for a way to trigger the browser's default handling of links, from Javascript code. Does such a mechanism exist? Toolkit-specific answers also welcome (especially for Gecko).

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• Unit testing a Grails custom taglib based on built-in Grails taglib

  - by dipess

  I've an app based on Grails 1.3.7. And I need to write a unit test for a custom taglib that is based on the built-in taglib, <g:select /> to be specific. I checked out the solution on this previous SO post but the solution stated is not working in my case (some properties are not being prooperly mocked up). The other solution that I found was this. Using this approach, I get most of the properties of FormTagLib mocked up except for the grailsApplication property that select requires. The actual error that I get is Cannot invoke method getArtefact() on null object. How can I properly write the unit test in such a case? Edit Here are my test class and the full stacktrace. Line #45 on the stacktrace is the call to the g.select from my custom taglib. My custom taglib is something like def clientSpecificQueues = {attrs-> def queueList = taskService.getClientSpecificQueues(session.clientName) def queueLabel = "Some String" if (queueList.size() > 0){ out << queueLabel else out << g.select(name:'queueId', from: queueList, optionKey: 'id', optionValue: 'name') }

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• Ruby TypeErrors involving `expected Data`

  - by Kenny Peng

  I've ran into situations where I have gotten these expected Data errors before, but they have always pointed to ActiveRecord not playing well with other libraries in the past. This piece of code: def load(kv_block, debug=false) # Converts a string block to a Hash using split kv_map = StringUtils.kv_array_to_hash(kv_block) # Loop through each key, value kv_map.each do |mem,val| # Format the member from camel case to underscore member = mem.camel_to_underscore() # If the object includes a method to set the key (i.e. the key # is a member of self), invoke the method, setting the value of # the member) if self.methods.include?(member.to_set_method_name()) then # Exception thrown here self.send(member.to_set_method_name(), val) # Else, check for the same case, this time for an instance variable elsif self.instance_variable_defined?(member.to_instance_var_name()) self.instance_variable_set(member.to_instance_var_name(), val) # Else, complain that the object doesn't understand the key with # respect to its class definition. else raise ArgumentError, "I don't know what to do with #{member}. #{self.class} does not have a member or function called #{member}" end end end produces the error wrong argument type #<Class:0x11a02088> (expected Data) (TypeError) in the each loop on the first if test. I've inspected a post-mortem debugging instance using rdebug, and running that line manually, it works without a hitch. Has anyone seen this error before and what's been your solution to it? I used to think it was ActiveRecord and other gems stomping on each other's definitions, but I removed any references to ActiveRecord and this still occurs.

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• Does "epsilon" really guarantees anything in floating-point computations?!

  - by Michal Czardybon

  To make the problem short let's say I want to compute expression: a / (b - c) on float's. To make sure the result is meaningful, I can check if 'b' and 'c' are inequal: float eps = std::numeric_limits<float>::epsilon(); if ((b - c) > EPS || (c - b) > EPS) { return a / (b - c); } but my tests show it is not enough to guarantee either meaningful results nor not failing to provide a result if it is possible. Case 1: a = 1.0f; b = 0.00000003f; c = 0.00000002f; Result: The if condition is NOT met, but the expression would produce a correct result 100000008 (as for the floats' precision). Case 2: a = 1e33f; b = 0.000003; c = 0.000002; Result: The if condition is met, but the expression produces not a meaningful result +1.#INF00. I found it much more reliable to check the result, not the arguments: const float INF = numeric_limits<float>::infinity(); float x = a / (b - c); if (-INF < x && x < INF) { return x; } But what for is the epsilon then and why is everyone saying epsilon is good to use?

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• C++: parsing with simple regular expression or shoud I use sscanf?

  - by Helltone

  I need to parse a string like func1(arg1, arg2); func2(arg3, arg4);. It's not a very complex parsing problem, so I would prefer to avoid resorting to flex/bison or similar utilities. My first approch was to try to use POSIX C regcomp/regexec or Boost implementation of C++ std::regex. I wrote the following regular expression, which does not work (I'll explain why further on). "^" "[ ;\t\n]*" "(" // (1) identifier "[a-zA-Z_][a-zA-Z0-9_]*" ")" "[ \t\n]*" "(" // (2) non-marking "\[" "(" // (3) non-marking "[ \t]*" "(" // (4..n-1) argument "[a-zA-Z0-9_]+" ")" "[ \t\n]*" "," ")*" "[ \t\n]*" "(" // (n) last argument "[a-zA-Z0-9_]+" ")" "]" ")?" "[ \t\n]*" ";" Note that the group 1 captures the identifier and groups 4..n-1 are intended to capture arguments except the last, which is captured by group n. When I apply this regex to, say func(arg1, arg2, arg3) the result I get is an array {func, arg2, arg3}. This is wrong because arg1 is not in it! The problem is that in the standard regex libraries, submarkings only capture the last match. In other words, if you have for instance the regex "((a*|b*))*" applied on "babb", the results of the inner match will be bb and all previous captures will have been forgotten. Another thing that annoys me here is that in case of error there is no way to know which character was not recognized as these functions provide very little information about the state of the parser when the input is rejected. So I don't know if I'm missing something here... In this case should I use sscanf or similar instead? Note that I prefer to use C/C++ standard libraries (and maybe boost).

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• leak in fgets when assigning to buffer

  - by monkeyking

  I'm having problems understanding why following code leaks in one case, and not in the other case. The difference is while(NULL!=fgets(buffer,length,file))//doesnt leak while(NULL!=(buffer=fgets(buffer,length,file))//leaks I thought it would be the same. Full code below. #include <stdio.h> #include <stdlib.h> #define LENS 10000 void no_leak(const char* argv){ char *buffer = (char *) malloc(LENS); FILE *fp=fopen(argv,"r"); while(NULL!=fgets(buffer,LENS,fp)){ fprintf(stderr,"%s",buffer); } fclose(fp); fprintf(stderr,"%s\n",buffer); free(buffer); } void with_leak(const char* argv){ char *buffer = (char *) malloc(LENS); FILE *fp=fopen(argv,"r"); while(NULL!=(buffer=fgets(buffer,LENS,fp))){ fprintf(stderr,"%s",buffer); } fclose(fp); fprintf(stderr,"%s\n",buffer); free(buffer); }

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• NHibernate mapping with two special cases

  - by brainimus

  I am using NHibernate to map a class to a database table. The Part table has an ID column (primary key) and a ParentPart column (along with a few others). class Part { public virtual long ID{ get; set; } public virtual Part ParentPart { get; set; } } The ParentPart is normally another valid part in the part table but I have two special cases. I have a case where the ParentPart column can be 0 (zero) and another case where it can be -1. Neither of these cases currently represent another valid Part object. I was thinking I could make 2 subclasses of Part (ZeroPart and NegativeOnePart) that would never persist. I want the zero and -1 values to be entered in the column but not persist the entire ZeroPart or NegativeOnePart objects. I am unsure how to map this (I'm using hbm files) or if this even the correct approach. How can I map this so that normal valid parts are persisted but I can also handle the special cases? As an aside: My current hbm file has the Part.ID's unsaved value as zero but I think I can just change this in the mapping to something different and default it in the class.

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