tail call optimization - Page 419

Exceptional C++[Bug]?

- by gautam kumar

I have been reading Exceptional C++ by Herb Sutter. On reaching Item 32 I found the following namespace A { struct X; struct Y; void f( int ); void g( X ); } namespace B { void f( int i ) { f( i ); // which f()? } } This f() calls itself, with infinite recursion. The reason is that the only visible f() is B::f() itself. There is another function with signature f(int), namely the one in namespace A. If B had written "using namespace A;" or "using A::f;", then A::f(int) would have been visible as a candidate when looking up f(int), and the f(i) call would have been ambiguous between A::f(int) and B::f(int). Since B did not bring A::f(int) into scope, however, only B::f(int) can be considered, so the call unambiguously resolves to B::f(int). But when I did the following.. namespace A { struct X; struct Y; void f( int ); void g( X ); } namespace B { using namespace A; void f( int i ) { f( i ); // No error, why? } } That means Herb Sutter has got it all wrong? If not why dont I get an error?

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Using groovy ws with enum types?

- by Jared

I'm trying to use groovy ws to call a webservice. One of the properties of the generated class is it's self a class with an enum type. Although the debug messages show that the com.test.FinalActionType is created at runtime when the WSDL is read I can't create an instance of it using code like proxy.create("com.test.FinalActionType") When I try and assign a string to my class uin place of an instance of FinalActionType groovy is not able to do the conversion. How can I get an instance of this class to use in a webservice call? I've pasted the important part of the WSDL below. <xsd:simpleType name="FinalActionType"> <xsd:restriction base="xsd:string"> <xsd:enumeration value="stop"/> <xsd:enumeration value="quit"/> <xsd:enumeration value="continue"/> <xsd:whiteSpace value="collapse"/> </xsd:restriction> </xsd:simpleType>

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Microsoft JScript runtime error Object doesn't support this property or method

- by Darxval

So i am trying to call this function in my javascript but it gives me the error of "Microsoft JScript runtime error Object doesn't support this property or method" and i cant figure out why. It is occuring when trying to call hmacObj.getHMAC. This is from the jsSHA website: http://jssha.sourceforge.net/ to use the hmac-sha1 algorithm encryption. Thank you! hmacObj = new jsSHA(signature_base_string,"HEX"); signature = hmacObj.getHMAC("hgkghk","HEX","SHA-1","HEX"); Above this i have copied the code from sha.js snippet: function jsSHA(srcString, inputFormat) { /* * Configurable variables. Defaults typically work */ jsSHA.charSize = 8; // Number of Bits Per character (8 for ASCII, 16 for Unicode) jsSHA.b64pad = ""; // base-64 pad character. "=" for strict RFC compliance jsSHA.hexCase = 0; // hex output format. 0 - lowercase; 1 - uppercase var sha1 = null; var sha224 = null; The function it is calling (inside of the jsSHA function) (snippet) this.getHMAC = function (key, inputFormat, variant, outputFormat) { var formatFunc = null; var keyToUse = null; var blockByteSize = null; var blockBitSize = null; var keyWithIPad = []; var keyWithOPad = []; var lastArrayIndex = null; var retVal = null; var keyBinLen = null; var hashBitSize = null; // Validate the output format selection switch (outputFormat) { case "HEX": formatFunc = binb2hex; break; case "B64": formatFunc = binb2b64; break; default: return "FORMAT NOT RECOGNIZED"; }

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Problem with function calls [javascript]

- by Samuel

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Is locking on the requested object a bad idea?

- by Quick Joe Smith

Most advice on thread safety involves some variation of the following pattern: public class Thing { private static readonly object padlock = new object(); private string stuff, andNonsense; public string Stuff { get { lock (Thing.padlock) { if (this.stuff == null) this.stuff = "Threadsafe!"; } return this.stuff; } } public string AndNonsense { get { lock (Thing.padlock) { if (this.andNonsense == null) this.andNonsense = "Also threadsafe!"; } return this.andNonsense; } } // Rest of class... } In cases where the get operations are expensive and unrelated, a single locking object is unsuitable because a call to Stuff would block all calls to AndNonsense, degrading performance. And rather than create a lock object for each call, wouldn't it be better to acquire the lock on the member itself (assuming it is not something that implements SyncRoot or somesuch for that purpose? For example: public string Stuff { get { lock (this.stuff) { // Pretend that this is a very expensive operation. if (this.stuff == null) this.stuff = "Still threadsafe and good?"; } return this.stuff; } } Strangely, I have never seen this approach recommended or warned against. Am I missing something obvious?

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jQuery select by two name roots and perform one of two function depending on which root was selected

- by RetroCoder

I'm trying to get this code to work in jQuery and I'm trying to make sure that for each iteration of each root element, its alternate root element for that same iteration doesn't contain anything. Otherwise it sets the .val("") property to an empty string. Looking for a simple solution if possible using search, find, or swap. Each matching number is on the same row level and the same iteration count. I have two input types of input text elements with two different root names like so: 1st Root is "rootA" <input type="text" name="rootA1" /> <input type="text" name="rootA2 /> <input type="text" name="rootA3" /> 2nd Root is "rootB" <input type="text" name="rootB1" /> <input type="text" name="rootB2 /> <input type="text" name="rootB3" /> On blur if any of rootA is called call function fnRootA();. On blur if any of rootB is called call function fnRootB();. Again, I'm trying to make sure that for each iteration like 1 that the alternate root doesn't contain anything, else it sets the .val("") property to an empty string of the root being blurred. My current code works for a single element but wanted to use find or search but not sure how to construct it.. $("input[name='rootA1']").blur(function(e) { fnRootA(1); // this code just removes rootA1's value val("") //if rootB1 has something in it value property // the (1) in parenthesis is the iteration number });

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xslt check for alpha numeric character

- by Newcoma

I want to check if a string contains only alphanumeric characters OR '.' This is my code. But it only works if $value matches $allowed-characters exactly. I use xslt 1.0. <xsl:template name="GetLastSegment"> <xsl:param name="value" /> <xsl:param name="separator" select="'.'" /> <xsl:variable name="allowed-characters">ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz.</xsl:variable> <xsl:choose> <xsl:when test="contains($value, $allowed-characters)"> <xsl:call-template name="GetLastSegment"> <xsl:with-param name="value" select="substring-after($value, $separator)" /> <xsl:with-param name="separator" select="$separator" /> </xsl:call-template> </xsl:when> <xsl:otherwise> <xsl:value-of select="$value" /> </xsl:otherwise> </xsl:choose> </xsl:template>

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Compiler turning a string& into a basic_string<>&

- by Shtong

Hello I'm coming back to C++ after long years spent on other technologies and i'm stuck on some weird behavior when calling some methods taking std::string as parameters : An example of call : LocalNodeConfiguration *LocalNodeConfiguration::ReadFromFile(std::string & path) { // ... throw configuration_file_error(string("Configuration file empty"), path); // ... } When I compile I get this (I cropped file names for readability) : /usr/bin/g++ -g -I/home/shtong/Dev/OmegaNoc/build -I/usr/share/include/boost-1.41.0 -o CMakeFiles/OmegaNocInternals.dir/configuration/localNodeConfiguration.cxx.o -c /home/shtong/Dev/OmegaNoc/source/configuration/localNodeConfiguration.cxx .../localNodeConfiguration.cxx: In static member function ‘static OmegaNoc::LocalNodeConfiguration* OmegaNoc::LocalNodeConfiguration::ReadFromFile(std::string&)’: .../localNodeConfiguration.cxx:72: error: no matching function for call to ‘OmegaNoc::configuration_file_error::configuration_file_error(std::string, std::basic_string<char, std::char_traits<char>, std::allocator<char> >&)’ .../configurationManager.hxx:25: note: candidates are: OmegaNoc::configuration_file_error::configuration_file_error(std::string&, std::string&) .../configurationManager.hxx:22: note: OmegaNoc::configuration_file_error::configuration_file_error(const OmegaNoc::configuration_file_error&) So as I understand it, the compiler is considering that my path parameter turned into a basic_string at some point, thus not finding the constructor overload I want to use. But I don't really get why this transformation happened. Some search on the net suggested me to use g++ but I was already using it. So any other advice would be appreciated :) Thanks

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Thread mutex behaviour

- by Alberteddu

Hi there, I'm learning C. I'm writing an application with multiple threads; I know that when a variable is shared between two or more threads, it is better to lock/unlock using a mutex to avoid deadlock and inconsistency of variables. This is very clear when I want to change or view one variable. int i = 0; /** Global */ static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER; /** Thread 1. */ pthread_mutex_lock(&mutex); i++; pthread_mutex_unlock(&mutex); /** Thread 2. */ pthread_mutex_lock(&mutex); i++; pthread_mutex_unlock(&mutex); This is correct, I think. The variable i, at the end of the executions, contains the integer 2. Anyway, there are some situations in which I don't know exactly where to put the two function calls. For example, suppose you have a function obtain(), which returns a global variable. I need to call that function from within the two threads. I have also two other threads that call the function set(), defined with a few arguments; this function will set the same global variable. The two functions are necessary when you need to do something before getting/setting the var. /** (0) */ /** Thread 1, or 2, or 3... */ if(obtain() == something) { if(obtain() == somethingElse) { // Do this, sometimes obtain() and sometimes set(random number) (1) } else { // Do that, just obtain(). (2) } } else { // Do this and do that (3) // If # of thread * 3 > 10, then set(3*10) For example. (4) } /** (5) */ Where I have to lock, and where I have to unlock? The situation can be, I think, even more complex. I will appreciate an exhaustive answer. Thank you in advance. —Alberto

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Java reflection appropriateness

- by jsn

This may be a fairly subjective question, but maybe not. My application contains a bunch of forms that are displayed to the user at different times. Each form is a class of its own. Typically the user clicks a button, which launches a new form. I have a convenience function that builds these buttons, you call it like this: buildButton( "button text", new SelectionAdapter() { @Override public void widgetSelected( SelectionEvent e ) { showForm( new TasksForm( args... ) ); } } ); I do this dozens of times, and it's really cumbersome having to make a SelectionAdapter every time. Really all I need for the button to know is what class to instantiate when it's clicked and what arguments to give the constructor, so I built a function that I call like this instead: buildButton( "button text", TasksForm.class, args... ); Where args is an arbitrary list of objects that you could use to instantiate TasksForm normally. It uses reflection to get a constructor from the class, match the argument list, and build an instance when it needs to. Most of the time I don't have to pass any arguments to the constructor at all. The downside is obviously that if I'm passing a bad set of arguments, it can't detect that at compilation time, so if it fails, a dialog is displayed at runtime. But it won't normally fail, and it'll be easy to debug if it does. I think this is much cleaner because I come from languages where the use of function and class literals is pretty common. But if you're a normal Java programmer, would seeing this freak you out, or would you appreciate not having to scan a zillion SelectionAdapters?

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Visual Studio 2008 linker wants all symbols to be resolved, not only used ones

- by user343011

We recently upgraded to Visual Studio 2008 from 2005, and I think those error started after that. In our solution, we have a multitude of projects. Many of those are utility projects, or projects containing core functionality used by other projects. The output of those is lib files that are linked to when building the projects generating the final binaries using the "Project dependencies..." option. One of the other projects---Let us call it ResultLib---generates a DLL, and it needs one single function from the core project. This function uses only static function from its own source file, but the project in its entirety uses a lot of low-level Windows functions and also imports a DLL---Let us call it Driver.dll. Our problem is that when building ExtLib, the linker complains about a multitude of unresolved externals, for example all functions exported from Driver.dll, since its lib file is not specified when linking. If we try to fix this by adding all lib files used by other projects that use all of the core project, our resulting ResultLib DLL ends up importing Driver.dll and also exporting all functions defined in it. How do we tell Visual Studio to only try to resolve symbols that are actually used?

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Centralizing Messagebox handling for application

- by DRapp

I'm wondering how others deal with trying to centralize MessageBox function calling. Instead of having long text embedded all over the place in code, in the past (non .net language), I would put system and application base "messagebox" type of messages into a database file which would be "burned" into the executable, much like a resource file in .Net. When a prompting condition would arise, I would just do call something like MBAnswer = MyApplication.CallMsgBox( IDUserCantDoThat ) then check the MBAnswer upon return, such as a yes/no/cancel or whatever. In the database table, I would have things like what the messagebox title would be, the buttons that would be shown, the actual message, a special flag that automatically tacked on a subsequent standard comment like "Please contact help desk if this happens.". The function would call the messagebox with all applicable settings and just return back the answer. The big benefits of this was, one location to have all the "context" of messages, and via constants, easier to read what message was going to be presented to the user. Does anyone have a similar system in .Net to do a similar approach, or is this just a bad idea in the .Net environment.

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JQuery dynamic .load - works for 1 and not for the other??

- by Alvin

UPDATE: Site is online http://qwickqual.com/memorial/create/ under "Memoria Media" - Click on "Our Videos" and it loads the list of categories click on any sub category and it goes through the process below ---------------- end edit ---------------------------------- UPDATED DESCRIPTION OF ERROR: All code is based on <li> objects being linked If I click on an <li> from the Initial page load to load: section 1: I can click on an <li> to load sub-categories section 2: I then click on an <li>, the query is made server returns section 3, section is not loaded to screen / and callback function is skipped over perhaps someone has run into a similar issue before?? ---------------- end edit ---------------------------------- I've also added comments to the code I have a jquery function that is setup to load categorized lists of thumbnails. So far the function is in use in 3 location. Each of them generates HTML using the same template under django. The function works perfectly in 2 of the 3 locations, and I"m plain stumped as to why the 3rd won't work. Below is the complete set of relevant javascript, the page load HTML for the relevant section. And 2 examples of HTML that is loaded through the script, 1 of them works, 1 of them doesn't and both are loaded into the same page load HTML Any ideas what I'm missing here? Or information I need to add to help debug? Currently posting this to a live server to interact with, been local only till now... Error: Script works properly through all levels of title="our_photos" Script loads 1st level of title="our_videos" Script will not load sub-category of title="our_videos" Example: From HTML below: Click on Script will query the server properly: GET http://localhost%3A8000/memorial/media%5Ftype/our%5Fvideos/4/ Script will not load the returned HTML into the #select_media div scopeChain: [Call, Call multi=false uri=/memorial/media_type/our_videos/, Window # 0=Call 1=Call 2=window] relative vars: label = "our_videos" wrapper = "media" uri = "/memorial/media_type/our_videos/" multi = false Javascript <script type="text/javascript"> // this piece is where I'm having trouble in the grand scheme of things // label = piece of class tag // wrapper = tag to load everything inside of // uri = base of the page to load // multi = not relevant for this piece but needed to pass on to next function function img_thumb_loader(label, wrapper, uri, multi) { if(!(wrapper)) { wrapper = label } $('.'+label+'_category').click(function () { // show the loading animation $('div#'+wrapper+'_load').show(); // get var of current object type = $(this).attr('title') || ''; // load it into the screen - this is the error // when I click on an <li> from section 2 below it will query server // (Tamper data & server see it - & return section 3 below // But will not load into the screen on return // also skips over the callback function $('#select_'+label).load(uri+type+'/', '', function() { $('div#'+wrapper+'_load').hide(); $('input.img_'+label+'_field').each(function() { img = $(this).attr('value'); $('li#img_'+label+'-'+img).css('selected_thumb'); }); img_thumb_selected(label); window[label+'_loader'](); }); }); $('.img_'+label).click(function () { if($(this).hasClass('selected_thumb')) { $(this).removeClass('selected_thumb'); id = $(this).attr('title'); $('.img_'+label+'_selected[value="'+id+'"]').remove(); } else { if(!(multi)) { previous = $('.img_'+label+'_selected').val(); $('#img_'+label+'-'+previous).removeClass('selected_thumb'); $('.img_'+label+'_selected').remove(); } $(this).addClass('selected_thumb'); id = $(this).attr('title'); $('#select_'+wrapper).after('<input class="img_'+label+'_selected" id="img_'+label+'_field-'+id+'" type="hidden" name="imgs[]" value="'+id+'" />'); } }); img_thumb_selected(label); } function img_thumb_selected(label) { $('.img_'+label+'_selected').each(function() { current = $(this).val(); if(current) { $('#img_'+label+'-'+current).addClass('selected_thumb'); } }); } function media_type() { $('.media_type').click(function () { $('#media_load').show(); type = $(this).attr('title') || ''; $('#select_media').load('/memorial/media_type/'+type+'/', '', function() { $('#select_media').wrapInner('<div id="select_'+type+'"></div>'); $('#select_media').append('<ul class="root_link"><h3><a class="load_media" onclick="return false;" href="#">Return to Select Media Type</a></h3></ul>'); load_media_type(); $('#media_load').hide(); window[type+'_loader'](); }); }); } media_type(); function load_media_type() { $('.load_media').click(function () { $('#media_load').show(); $('#select_media').load('{% url mem_media_type %}', '', function() { $('#media_load').hide(); media_type(); }); }); } function our_photos_loader() { img_thumb_loader('our_photos', 'media', '{% url mem_our_photos %}', true); } function our_videos_loader() { img_thumb_loader('our_videos', 'media', '{% url mem_our_videos %}', false); } </script> HTML - Initial Page load <fieldset> <legend>Memorial Media</legend> <div style="display: none;" id="media_load" class="loading"/> <div id="select_media"> <ul style="width: 528px;" class="initial"> <li title="your_photos" class="media_type"><div class="photo_select_upload"><h3>Your Photos</h3></div></li> <li title="our_photos" class="media_type"><div class="photo_select"><h3>Our Photos</h3></div></li> <li title="our_videos" class="media_type"><div class="video_select"><h3>Our Videos</h3></div></li> </ul> </div> </fieldset> HTML - Returned from Click on section 1 this section can make calls to subcategories and it will work <br class="clear" /> <ul class="thumb_sub_category" style="width: 352px;"> <li id="our_photos_category-29" class="our_photos_category" title="29"> <div> <span style="background-image: url(/site_media/photologue/photos/cache/stuff_004_thumbnail.jpg);" class="thumb"><span></span></span> <p>Birds 1</p> </div> </li> <li id="our_photos_category-25" class="our_photos_category" title="25"> <div> <span style="background-image: url(/site_media/photologue/photos/cache/dsc_0035_thumbnail.jpg);" class="thumb"><span></span></span> <p>Dogs 1</p> </div> </li> </ul> HTML - Returned from click on Section 2 Having trouble with sub-categories from this area <br class="clear" /> <ul class="thumb_sub_category" style="width: 528px;"> <li id="our_videos_category-1" class="our_videos_category" title="1"> <div> <span style="background-image: url(/site_media/photologue/photos/cache/forest-1_thumbnail.jpg);" class="thumb"><span></span></span> <p>Video 1</p> </div> </li> <li id="our_videos_category-3" class="our_videos_category" title="3"> <div> <span style="background-image: url(/site_media/photologue/photos/cache/mountain-1_thumbnail.jpg);" class="thumb"><span></span></span> <p>Video 3</p> </div> </li> <li id="our_videos_category-4" class="our_videos_category" title="4"> <div> <span style="background-image: url(/site_media/photologue/photos/cache/mountain-3_thumbnail.jpg);" class="thumb"><span></span></span> <p>Video 4</p> </div> </li> </ul> HTML that fails to load inside - Section 3 <br class="clear" /> <ul class="thumb_sub_category" style="width: 528px;"> <li id="our_videos_category-1" class="our_videos_category" title="1"> <div> <span style="background-image: url(/site_media/photologue/photos/cache/forest-1_thumbnail.jpg);" class="thumb"><span></span></span> <p>Video 1</p> </div> </li> <li id="our_videos_category-3" class="our_videos_category" title="3"> <div> <span style="background-image: url(/site_media/photologue/photos/cache/mountain-1_thumbnail.jpg);" class="thumb"><span></span></span> <p>Video 3</p> </div> </li> <li id="our_videos_category-4" class="our_videos_category" title="4"> <div> <span style="background-image: url(/site_media/photologue/photos/cache/mountain-3_thumbnail.jpg);" class="thumb"><span></span></span> <p>Video 4</p> </div> </li> </ul>

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Dynamic Select boxes page load

- by Chris

Hello, I have a dynamic chained select box that I am attempting to show the value of on a page load. In my chained select box, it will default to the first option within the select box on page load, could anyone provide assitance? I stumbled upon this thread, but I can't seem to translate what they are doing with that answer to my language of CF. Dynamic chained drop downs on page refresh Here is the JS script I am using. function dynamicSelect(id1, id2) { // Feature test to see if there is enough W3C DOM support if (document.getElementById && document.getElementsByTagName) { // Obtain references to both select boxes var sel1 = document.getElementById(id1); var sel2 = document.getElementById(id2); // Clone the dynamic select box var clone = sel2.cloneNode(true); // Obtain references to all cloned options var clonedOptions = clone.getElementsByTagName("option"); // Onload init: call a generic function to display the related options in the dynamic select box refreshDynamicSelectOptions(sel1, sel2, clonedOptions); // Onchange of the main select box: call a generic function to display the related options in the dynamic select box sel1.onchange = function() { refreshDynamicSelectOptions(sel1, sel2, clonedOptions); } } } function refreshDynamicSelectOptions(sel1, sel2, clonedOptions) { // Delete all options of the dynamic select box while (sel2.options.length) { sel2.remove(0); } // Create regular expression objects for "select" and the value of the selected option of the main select box as class names var pattern1 = /( |^)(select)( |$)/; var pattern2 = new RegExp("( |^)(" + sel1.options[sel1.selectedIndex].value + ")( |$)"); // Iterate through all cloned options for (var i = 0; i < clonedOptions.length; i++) { // If the classname of a cloned option either equals "select" or equals the value of the selected option of the main select box if (clonedOptions[i].className.match(pattern1) || clonedOptions[i].className.match(pattern2)) { // Clone the option from the hidden option pool and append it to the dynamic select box sel2.appendChild(clonedOptions[i].cloneNode(true)); } } } Thanks so much for any assistance

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C++ - Basic WinAPI question

- by HardCoder1986

Hello! I am now working on a some sort of a game engine and I had an idea to put everything engine-related into a static library and then link it to my actual problem. Right now I achieved it and actually link that library and every functions seem to work fine, except those, which are windows-related. I have a chunk of code in my library that looks like this: hWnd = CreateWindow(className, "Name", WS_OVERLAPPED | WS_CAPTION | WS_EX_TOPMOST, 0, 0, 800, 600, NULL, NULL, GetModuleHandle(NULL), this); if (hWnd) { ShowWindow(hWnd, SW_NORMAL); UpdateWindow(hWnd); } else { MessageBox(NULL, "Internal program error", "Error", MB_OK | MB_ICONERROR); return; } When this code was not in the library, but in the actual project, it worked fine, created the window and everything was ok. Right now (when I'm linking to my library that contains this code) CreateWindow(...) call returns NULL and GetLastError() returns "Operation succesfully completed" (wtf?). Could anybody help me with this? Is it possible to create a window and display it using a static library call and why could my code fail? Thank you.

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PHP / Zend custom date input formats

- by mld

Hi, I'm creating a library component for other developers on my team using PHP and Zend. This component needs to be able to take as input a date (string) and another string telling it the format of that date. Looking through the Zend documentation and examples, I thought I found the solution - $dateObject = Zend_Date('13.04.2006', array('date_format' => 'dd.MM.yyyy')); this line, however, throws an error - call to undefined function. So instead I tried this - $dt = Zend_Locale_Format::getDate('13.04.2006', array('date_format' => 'dd.MM.yyyy')); This gets the job done, but throws an error if a date that is entered isn't valid. The docs make it look like you can use the isDate() function to check validity - Zend_Date::isDate('13.04.2006', array('date_format' => 'dd.MM.yyyy')) but this line always returns false. So my questions - Am I going about this the right way? If not, is there a better way to handle this via Zend or straight PHP? If I do use Zend_Locale_Format::getDate(), do I need to worry about a locale being set elsewhere and changing the results of the call? I'm locked into PHP 5.2.6 on windows, btw... so 5.3+ functions & strptime() are out.

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Run Reporting Service in local mode and generate columns automatically?

- by grady

Hi, I have a SQL query right now which I want to use with the MS reporting services in my ASP.NET application. So I created a report in local mode (rdlc) and attached this to a report viewer. Since my query uses parameters, I created a stored procedure, which had exactly those parameters. In addition to that I had some textboxes which are used for entering the params for the query and a button to call the stored proc and to fill the datatset which is bound to the report viewer. This works, I press the button and according to what I entred the correct data is shown. Now my question: In the future I plan to have multiple reports (which will be selected in a dropdown) and I wonder if I can somehow just call the correct stored procedure and according to the columns which are *SELECT*ed in the procedure, the columns are shown in the report. Example: I select report1 from the dropdown (procedure for report 1 is called), 5 columns are shown in the reportviewer. I select report2 from dropdown (procedure for report 2 is called), 8 columns are shown. Is that possible somehow? Thanks :-)

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How to write a "thread safe" function in C ?

- by Andrei Ciobanu

Hello I am writing some data structures in C, and I've realized that their associated functions aren't thread safe. The i am writing code uses only standard C, and I want to achieve some sort of 'synchronization'. I was thinking to do something like this: enum sync_e { TRUE, FALSE }; typedef enum sync_e sync; struct list_s { //Other stuff struct list_node_s *head; struct list_node_s *tail; enum sync_e locked; }; typedef struct list_s list; , to include a "boolean" field in the list structure that indicates the structures state: locked, unlocked. For example an insertion function will be rewritten this way: int list_insert_next(list* l, list_node *e, int x){ while(l->locked == TRUE){ /* Wait */ } l->locked = TRUE; /* Insert element */ /* -------------- */ l->locked = FALSE; return (0); } While operating on the list the 'locked' field will be set to TRUE, not allowing any other alterations. After operation completes the 'locked' field will be again set to 'TRUE'. Is this approach good ? Do you know other approaches (using only standard C).

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System Calls in windows & Native API?

- by claws

Recently I've been using lot of Assembly language in *NIX operating systems. I was wondering about the windows domain. Calling convention in linux: mov $SYS_Call_NUM, %eax mov $param1 , %ebx mov $param2 , %ecx int $0x80 Thats it. That is how we should make a system call in linux. Reference of all system calls in linux: Regarding which $SYS_Call_NUM & which parameters we can use this reference : http://docs.cs.up.ac.za/programming/asm/derick_tut/syscalls.html OFFICIAL Reference : http://kernel.org/doc/man-pages/online/dir_section_2.html Calling convention in Windows: ??? Reference of all system calls in Windows: ??? Unofficial : http://www.metasploit.com/users/opcode/syscalls.html , but how do I use these in assembly unless I know the calling convention. OFFICIAL : ??? If you say, they didn't documented it. Then how is one going to write libc for windows without knowing system calls? How is one gonna do Windows Assembly programming? Atleast in the driver programming one needs to know these. right? Now, whats up with the so called Native API? Is Native API & System calls for windows both are different terms referring to same thing? In order to confirm I compared these from two UNOFFICIAL Sources System Calls: http://www.metasploit.com/users/opcode/syscalls.html Native API: http://undocumented.ntinternals.net/aindex.html My observations: All system calls are beginning with letters Nt where as Native API is consisting of lot of functions which are not beginning with letters Nt. System Call of windows are subset of Native API. System calls are just part of Native API. Can any one confirm this and explain.

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jQuery.data() works in Mac OS WebKit, but not on iPhone OS?

- by rpj

I'm playing around with jQTouch for an iPhone OS app that I've been toying with off and on for a while. I wanted to try my hand building it as a web app so I started playing with jQTouch. For reference, here is the page+source (all my code is currently in index.html so you can just "View Source" to see it all): http://rpj.me/doughapp.com/wd/ Essentially, I'm trying to save pertinent JSON objects retrieved from Google Local into DOM objects using the data() method (in this example, obj is the Google Local object): $('#locPane').data('selected', obj); then later (in a different "pane"), retrieving that object to be used: $('#locPane').bind('pageAnimationEnd', function(e, inf) { var selobj = $(this).data('selected'); // use 'selobj' here ... } In Chromium and Safari on the desktop OS (Snow Leopard in my case), this works perfectly (try it out). However, the same code returns undefined for the call to $(this).data('selected') in the second snippet above. I've also tried $('#' + e.target.id).data('selected') and even the naive $('#locPane').data('selected'). All variants return undefined in the iPhone OS version of WebKit, but not on the desktop. Interestingly, the running this on Mobile Safari in the iPhone Simulator fails as well. If you look at the full source, you'll see that I even try to save this object into my global jQTouch object (named jqt in my code). This, too, fails on the mobile platform. Has anyone else ever ran into this? I'll admit to not being a web/javascript programmer by trade, so if I'm making an idiot's error please call me out on it. Thank you in advance for the help! -RPJ Update: I didn't make it clear in the original post, but I'm open to any workaround if it works consistently. Since I'm having trouble storing these objects in general, anything that allows me to keep them around is good enough for now. Thanks!

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2 dimensional arrays passed to a function in c++

- by John Marcus

I'm working on doing calculations in a two dimensional array but keep getting a nasty error. i call the function by : if(checkArray(array)) and try to pass it in like this: bool checkArray(double array[][10]) //or double *array[][10] to no avail the error is error: cannot convert ‘double ()[(((unsigned int)(((int)n) + -0x00000000000000001)) + 1)]’ to ‘double’ for argument ‘1’ to ‘bool checkArray(double*)’ code snippet //array declaration int n = 10; double array[n][n]; //function call to pass in array while(f != 25) { cout<<endl; cout<<endl; if(checkArray(array)) //this is the line of the error { cout<<"EXIT EXIT EXIT"<<endl; } f++; } //function declaration bool checkArray(double *array)//, double newArray[][10]) { double length = sizeof(array); for(int i = 0; i < length; i++) for(int j = 0; j < length;j++) { double temp = array[i][j]; } }

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Minimizing server load in case of many XMLHttpRequest calls

- by user1888975

I am making a website where users are to like some articles. Whenever the like button is clicked I am sending a XMLHttpRequest to the server to run a file called like_clicked.php along with the get data of article id and user id. This file takes article id and user id and updates the sql database and also adds a node in an xml file related to the user. This is the first time I am doing something for mass usage. I am worried about the server load when too many users call the like_clicked.php file. Please help me, if this method is ok. I am also thinking of an alternative in case the above method fails. I am thinking of making many like_clicked files (namely like_clicked1.php, like_clicked2.php ... ) to minimize load on a single i-node. Is there a method to detect that it is better to call the next like_clicked file. Here we would need to detect how many calls per unit time are coming for the particular file. How do we handle this? Thanks in advance.

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Jquery Ajax + PHP

- by Kris.Mitchell

I am having problems with jQuery Ajax and PHP I have my php file set up to echo the data I am gathering from a mysql database. I have verified that the database is returning something and that the string at the end of the function actually contains data. What is happening though, is that it looks like the php echo is happening before the ajax call, causing the php data to be displayed at the top of the page, and not below in proper div. I think it might have something to do with timing of the ajax and the php call, but I am not sure. So, why is the data not getting caught by the .ajax and thrown into the div? Thanks for the help! jQuery $(document).ready(function() { $.ajax({ url: "../database_functions.php", type: "GET", data: "cat=jw&sub=pi&sort=no", cache: false, success: function (html) { alert("Success!"); $('#product-list').html(html); } }); }); PHP echo "Hello World";

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What wrapper class in C++ should I use for automated resource management?

- by Vilx-

I'm a C++ amateur. I'm writing some Win32 API code and there are handles and weirdly compositely allocated objects aplenty. So I was wondering - is there some wrapper class that would make resource management easier? For example, when I want to load some data I open a file with CreateFile() and get a HANDLE. When I'm done with it, I should call CloseHandle() on it. But for any reasonably complex loading function there will be dozens of possible exit points, not to mention exceptions. So it would be great if I could wrap the handle in some kind of wrapper class which would automatically call CloseHandle() once execution left the scope. Even better - it could do some reference counting so I can pass it around in and out of other functions, and it would release the resource only when the last reference left scope. The concept is simple - but is there something like that in the standard library? I'm using Visual Studio 2008, by the way, and I don't want to attach a 3rd party framework like Boost or something.

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Pass object from JSON into MVC Controller - its always null ?

- by SteveCl

Hi I have seen a few questions on here related to the a similar issue, I have read them, followed them, but still i have the same problem. I am basically creating an object in javascript and trying to call a method on the controller that will return a string of html. Not JSON. I've been playing around with dataType and contentType but still no joy. So apologies if the code snippets are a bit messy. Build the object in JS. function GetCardModel() { var card = {}; card.CardTitle = $("#CardTitle").val(); card.TopicTitle = $("#TopicTitle").val(); card.TopicBody = $("#TopicBody").data("tEditor").value(); card.CardClose = $("#CardClose").val(); card.CardFromName = $("#CardFromName").val(); return card; } Take a look at the object - all looks good and as it should in JSON. var model = GetCardModel(); alert(JSON.stringify(GetCardModel())); Make the call... $.ajax({ type: "POST", url: "/Postcard/Create/Preview/", dataType: "json", //contentType: "application/json", date: GetCardModel(), processData: true, success: function (data) { alert("im back"); alert(data); }, error: function (xhr, ajaxOptions, error) { alert(xhr.status); alert("Error: " + xhr.responseText); //alert(error); } }); Always when I step into the controller, the object is ALWAYS there, but with null values for all the properties.

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