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• Source code dependency manager for C++

  - by 7vies

  There are already some questions about dependency managers here, but it seems to me that they are mostly about build systems, while I am looking for something targeted purely at making dependency tracking and resolution simpler (and I'm not necessarily interested in learning a new build system). So, typically we have a project and some common code with another project. This common code is organized as a library, so when I want to get the latest code version for a project, I should also go get all the libraries from the source control. To do this, I need a list of dependencies. Then, to build the project I can reuse this list too. I've looked at Maven and Ivy, but I'm not sure if they would be appropriate for C++, as they look quite heavily java-targeted (even though there might be plugins for C++, I haven't found people recommending them). I see it as a GUI tool producing some standardized dependency list which can then be parsed by different scripts etc. It would be nice if it could integrate with source control (tag, get a tagged version with dependencies etc), but that's optional. Would you have any suggestions? Maybe I'm just missing something, and usually it's done some other way with no need for such a tool? Thanks.

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• Looking forward to a programming future but confused where to start.

  - by Kraivyne

  Hi there, I am very new to this site and to programming. I started doing some basic programming with python a few weeks ago and recently, messing around with Java basics. My main problem is that I am completely overwhelmed and haven't got the slightest clue where I should be starting. I want to learn programming because I really enjoy doing it, the simple applications that I have managed to conjure up put a smile on my face. My plan is to eventually (by eventually I'm talking about 6 years+) go into games programming. I have been informed that C++ is the best way to go about this but haven't got the slightest clue what book/sight is optimal for someone who is still learning the very basics. These are my questions: I have been to the Definitive C++ Book Guide but am still unsure which book is best to start of with. Should I stick with Python or Java instead of moving on to C++? Is there any advice you would give to a beginner programmer? Thanks again for all your help.

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• How to call a method after asynchronous task is complete

  - by doctordoder

  I have a class called WikiWebView which is a subclass of UIWebView which loads Wikipedia subjects and is designed to fetch all the links of the webpage, in order to create a sort of site map for the subject. My problem is that I can only create the links once the web page has loaded, but the loading isn't done right after [self loadRequest:requestObj] is called. - (void)loadSubject:(NSString *)subject { // load the actual webpage NSString *wiki = @"http://www.wikipedia.org/wiki/"; NSString *fullURL = [wiki stringByAppendingString:subject]; NSURL *url = [NSURL URLWithString:fullURL]; NSURLRequest *requestObj = [NSURLRequest requestWithURL:url]; [self loadRequest:requestObj]; // [self createLinks]; // need this to be called after the view has loaded } - (void)createLinks { NSString *javascript = @"var string = \"\";" "var arr = document.getElementsByClassName(\"mw-redirect\");" "for (var i = 0; i < arr.length; ++i)" "{" "var redirectLink = arr[i].href;" "string = string + redirectLink + \" \";" "}" "string;"; NSString *links = [self stringByEvaluatingJavaScriptFromString:javascript]; self.links = [links componentsSeparatedByString:@" "]; } I tried the normal delegation technique, which lead to this code being added: - (id)init { if (self = [super init]) { self.delegate = self; // weird } return self; } #pragma mark - UIWebViewDelegate - (void)webViewDidStartLoad:(UIWebView *)webView { ++_numProcesses; } - (void)webView:(UIWebView *)webView didFailLoadWithError:(NSError *)error { --_numProcesses; } - (void)webViewDidFinishLoad:(UIWebView *)webView { --_numProcesses; if (_numProcesses == 0) { [self createLinks]; } } However, the delegate methods are never called.. I've seen similar questions where the answers are to use blocks, but how would I do that in this case?

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• How to create several records in only one dynamic form?

  - by Fernando

  Hi experts, please help me with a simple PHP doubt. I have a simple form: < form action="foo" Person: < a href="javascript:addmore();"Add More < /form Every time the user clicks Add More two new input fields will be dynamically created using jQuery. This can be done several times in a same form. < form action="foo" Person: < a href="javascript:addmore();"Add More < /form Each pair (name and last_name) should create on record in my db. Two Questions: 1) What is the best option for input id? Appending a counter is the best option? 2) How can I handle it in the backend using php? Let me know if you need more info. Thanks in advance.

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• Problem understanding Inheritance

  - by dhruvbird

  I've been racking my brains over inheritance for a while now, but am still not completely able to get around it. For example, the other day I was thinking about relating an Infallible Human and a Fallible Human. Let's first define the two: Infallible Human: A human that can never make a mistake. It's do_task() method will never throw an exception Fallible Human: A human that will occasionally make a mistakes. It's do_task() method may occasionally throw a ErrorProcessingRequest Exception The question was: IS an infallible human A fallible human OR IS a fallible human AN infallible human? The very nice answer I received was in the form of a question (I love these since it gives me rules to answer future questions I may have). "Can you pass an infallible human where a fallible human is expected OR can you pass a fallible human where an infallible human is expected?" It seems apparent that you can pass an infallible human where a fallible human is expected, but not the other way around. I guess that answered my question. However, it still feels funny saying "An infallible human is a fallible human". Does anyone else feel queasy when they say it? It almost feels as if speaking out inheritance trees is like reading out statements from propositional calculus in plain English (the if/then implication connectives don't mean the same as that in spoken English). Does anyone else feel the same?

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• MySQL Join/Comparison on a DATETIME column (<5.6.4 and > 5.6.4)

  - by Simon

  Suppose i have two tables like so: Events ID (PK int autoInc), Time (datetime), Caption (varchar) Position ID (PK int autoinc), Time (datetime), Easting (float), Northing (float) Is it safe to, for example, list all the events and their position if I am using the Time field as my joining criteria? I.e.: SELECT E.*,P.* FROM Events E JOIN Position P ON E.Time = P.Time OR, even just simply comparing a datetime value (taking into consideration that the parameterized value may contain the fractional seconds part - which MySQL has always accepted) e.g. SELECT E.* FROM Events E WHERE E.Time = @Time I understand MySQL (before version 5.6.4) only stores datetime fields WITHOUT milliseconds. So I would assume this query would function OK. However as of version 5.6.4, I have read MySQL can now store milliseconds with the datetime field. Assuming datetime values are inserted using functions such as NOW(), the milliseconds are truncated (<5.6.4) which I would assume allow the above query to work. However, with version 5.6.4 and later, this could potentially NOT work. I am, and only ever will be interested in second accuracy. If anyone could answer the following questions would be greatly appreciated: In General, how does MySQL compare datetime fields against one another (consider the above query). Is the above query fine, and does it make use of indexes on the time fields? (MySQL < 5.6.4) Is there any way to exclude milliseconds? I.e. when inserting and in conditional joins/selects etc? (MySQL 5.6.4) Will the join query above work? (MySQL 5.6.4) EDIT I know i can cast the datetimes, thanks for those that answered, but i'm trying to tackle the root of the problem here (the fact that the storage type/definition has been changed) and i DO NOT want to use functions in my queries. This negates all my work of optimizing queries applying indexes etc, not to mention having to rewrite all my queries. EDIT2 Can anyone out there suggest a reason NOT to join on a DATETIME field using second accuracy?

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• Linq-to-sql join/where?

  - by Curtis White

  I've the following table structures Users id Types id isBool UsersTypes userid types I want to select all the UserTypes based on id and isBool. I tried this query var q = from usertype in usertypes from type in types where type.isBool == false where userstypes.user == id select usertype; But this did not work as expected. My questions are: Why? Is there any difference in using the join on syntax vs where, where vs where cond1 && cond2? My understanding is query optimizer will optimize. Is there any difference in using where cond1 == var1 && cond2 == var2 with and without the parenthesis? This seems peculiar that it is possible to build this without parenthesis What type of query do I need in this case? I can see that I could do a subquery or use a group but not 100% sure if it is required. An example might be helpful. I'm thinking a subquery may be required in this case.

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• How can you pass an object from the form_for helper to a method?

  - by Alex

  So let's say I have a form which is being sent somewhere strange (and by strange we mean, NOT the default route: <% form_for @form_object, :url => {:controller => 'application', :action => 'form_action_thing'} do |f| %> <%= f.text_field :email %> <%= submit_tag 'Login' %> <% end %> Now let's say that we have the method that accepts it. def form_action_thing User.find(????? :email ?????) end My questions are thus: How does can I make the object @form_object available to the receiving method (in this case, form_action_tag)? I've tried params[:form_object], and I've scoured this site and the API, which I have to post below because SO doesn't believe I'm not a spammer (I'm a new member), as well as Googled as many permutations of this idea as I could think of. Nothing. Sorry if I missed something, i'm really trying. How do I address the object, once I've made it accessible to the method? Not params[:form_object], I'm guessing.

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• What's the steps for SQL optimization and changes without reflect live system ?

  - by Space Cracker

  we have a big portal that build using SharePoint 2007 , asp.net 3.5 , SQL Server 2005 .. many developers work in it since 01/2008 and we are now doing huge analysis for current SQL Databases [not share-point DB ] to optimize and enhance it. The main db have about 330 table and 1720 stored procedure (SP) created from 01/2008 till now Many table names / Columns is very long and we want to short it we found SP names is written in 25 format :( , some of them are very complex and also we want to rename many SP parameters need to be renamed one of the biggest table is Registered user table, that will be spitted in more than one table for some optimization, many columns name will be changed I searched for the way that i can rename table names ,columns and i found SQL refactor tool but i still trying it .. my questions : Is SQl Refactor is the best tool for renaming ? or is there any other one ? if i want to make it manually, is there any references or best practice for that ? How can i do such changes in fast and stable way .. i search for recommendations and case studies if exist ?

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• How to access parents' members from a inner class in WPF?

  - by black sensei

  Hello Experts! I'm trying to do scheduled operation let's say to check for user's credit left via web service call and update the user interface. i've tried with quartz.net to implement the scheduling bit.i created an inner class in the window class i need to update.That inner class has the method that calls the webservice and the result needs to be displayed back to the UI. here is an example of what i did. public partial class Window2 : Window { private int i; public Window2() { InitializeComponent(); } public class Myclass :IJob { public void Execute(JobExecutionContext context) { string result = doMyOperation(); //i'll like to call parent label member of name lblNotif //is something like parent.lblNotif.Content = result; //possible? } public string doMyOperation() { //calling the wermethod to retreive user's balance return result = service.GetUsersBalace(user); } } } Well the quartz bit is working and this post is not about quartz. here are my questions Question 1 : How is it possible to access Window2 controls, for instace lable lblNotif? Question 2 : If my thinking about this is wrong, what is done as best practice to solve my kind of problem, where an application need to do an operation let's say every 5mn and update the the UI. Question 3 : i at first tried to use the backgroundworker and i felt like i can't do the scheduling bit with it.Is that correct or i'm wrong. thanks for those who commented already and sorry for those who didn't get the meaning of my post.I hope this will be a bit clearer.Thanks for reading

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• Context path routing in Tomcat ( service swapping )

  - by jojovilco

  Here is what I would like to achieve: I have a web service A which I want to be able to deploy side by side with other web services of type A - different version(s). For now I assume 2 instances side by side. I need it because the service has a warm up stage, which takes some time to build up stuff from DB and only after it is ready it can start serving requests ... I was thinking to deploy to Tomcat context paths like: "/ServiceA-1.0", "/ServiceA-2.0" and then have a "virtual" context like "/ServiceA" which will point to the desired physical service e.g. "/ServiceA-1.0". So external world will know about ServiceA, but internally, my ServiceA related stack would know about versioned ServiceA url ( there are more components involved but only ServiceA is serving outer world ). When new service is ready, I would just reconfigure the "virtual" context to point to a new service. So far, I was not able to find out how to do this with Tomcat and starting to tkink it is not possible. I found suggestions to place Apache Server in front of Tomcat and do the routing there, but I do not want to enroll another piece of software unless necessary. My questions are: - is this kind of a "virtual" context and routing possible to do with Tomcat? - any other options, wisdom and lessons learned how to achieve this kind of service swapping scenario? Best, Jozef

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• How do I simplify my code?

  - by Mitchell Skurnik

  I just finished creating my first major application in C#/Silverlight. In the end the total line count came out to over 12,000 lines of code. Considering this was a rewrite of a php/javascript application I created 2 years that was over 28,000 lines I am actually quite proud of my accomplishment. After reading many questions and answers here on stackoverflow and other sites online, I followed many posters advice: I created classes, procedures, and such for things that I would have a year ago copied and pasted; I created logic charts to figure out complex functions; making sure there are no crazy hidden characters (used tabs instead of spaces); and a few others things; place comments where necessary (I have lots of comments). My application consists of 4 tiles laid out horizontally that have user controls loaded into each slice. You can have between one and four slices loaded at anytime. If you have once slice loaded, the slice takes up the entire artboard...if you have 2 loaded, each take up half, 3 a third, 4 a quarter. Each one of these slices represent (for the sake of this example) a light control. Each slice has 3 slider controls in it. Now when I coded the functionality of the sliders, I used a switch/case statement inside of a public function that would run the command on the specified slice/slider. The made for some duplicate code but I saw no way around it as each slice was named differently. So I would do slice1.my.commands(); slice2.my.commands(); etc. My question to you is how do I clean up my code even futher? (Sadly I cannot post any of my code). Is there any way to take this repetion out of my code?

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• How do I insert XML into another XML file with XSLT?

  - by Sandra

  Hello, I looked at this thread to find out how to insert XML into XML with XSLT http://stackoverflow.com/questions/862954/insert-xml-node-at-a-specific-position-of-an-existing-document But I have a problem since I need to insert XML between two grand child nodes. For example I want to insert <s>...</s> between <r>...</r> and <t>...</t> in this file <root> <child1> <a>...</a> <r>...</r> <t>...</t> <z>...</z> </child1> </root> to create this file <root> <child1> <a>...</a> <r>...</r> <s>...</s> <t>...</t> <z>...</z> </child1> </root> Thanks for your help.

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• Overlay an image over video using OpenGL ES shaders

  - by BlueVoodoo

  I am trying to understand the basic concepts of OpenGL. A week into it, I am still far from there. Once I am in glsl, I know what to do but I find getting there is the tricky bit. I am currently able to pass in video pixels which I manipulate and present. I have then been trying to add still image as an overlay. This is where I get lost. My end goal is to end up in the same fragment shader with pixel data from both my video and my still image. I imagine this means I need two textures and pass on two pixel buffers. I am currently passing the video pixels like this: glGenTextures(1, &textures[0]); //target, texture glBindTexture(GL_TEXTURE_2D, textures[0]); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_BGRA, GL_UNSIGNED_BYTE, buffer); Would I then repeat this process on textures[1] with the second buffer from the image? If so, do I then bind both GL_TEXTURE0 and GL_TEXTURE1? ...and would my shader look something like this? uniform sampler2D videoData; uniform sampler2D imageData; once I am in the shader? It seems no matter what combination I try, image and video always ends up being just video data in both these. Sorry for the many questions merged in here, just want to clear my many assumptions and move on. To clarify the question a bit, what do I need to do to add pixels from a still image in the process described? ("easy to understand" sample code or any types of hints would be appreciated).

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• How to disable Rails submit buttons alongside Prototype helpers & RJS?

  - by Jesse

  I'm trying to follow this post http://stackoverflow.com/questions/576240/how-can-i-unobtrusively-disable-submit-buttons-with-javascript-and-prototype but I can't get it to work. The form triggers an RJS function, so I need to keep the helpers' onclick events intact. The RJS returns/reloads the same forms along with two new texts. I'm really confused. Here is my rails code for the forms: .span-20#comparison / new comparison . . . / voting forms (also reloaded) .span-4.prepend-3.append-6 - form_remote_tag :action => url_for(:controller => :comparisons), :method => :post do = hidden_field_tag :poem1_id, poems[:a].id = hidden_field_tag :poem2_id, poems[:b].id = hidden_field_tag :response, 1 = submit_tag "Vote for me", :disabled => false, :disable_with => 'Vote for me', :class => "compare" .span-4.append-3.last - form_remote_tag :action => url_for(:controller => :comparisons), :method => :post do = hidden_field_tag :poem1_id, poems[:a].id = hidden_field_tag :poem2_id, poems[:b].id = hidden_field_tag :response, 2 = submit_tag "Vote for me", :disable_with => 'Vote for me', :class => "compare" .span-4.prepend-8.append-8.prepend-top.last - form_remote_tag :action => url_for(:controller => :comparisons), :method => :post do = hidden_field_tag :poem1_id, poems[:a].id = hidden_field_tag :poem2_id, poems[:b].id = hidden_field_tag :response, 'draw' = submit_tag "Declare Draw", :disable_with => 'Declare Draw', :class => "compare" RJS page.replace_html :comparison, :partial => 'poems', :object => @poems page.insert_html :top, :previous, :partial => 'comparison', :object => @comparison page << "Effect.ScrollTo($('top'));"

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• How do disable Rails submit buttons alongside Prototype helpers & RJS?

  - by Jesse

  I'm trying to follow this post http://stackoverflow.com/questions/576240/how-can-i-unobtrusively-disable-submit-buttons-with-javascript-and-prototype but I can't get it to work. The form triggers an RJS function, so I need to keep the helpers' onclick events intact. The RJS returns/reloads the same forms along with two new texts. I'm really confused. Here is my rails code for the forms: .span-20#comparison / new comparison . . . / voting forms (also reloaded) .span-4.prepend-3.append-6 - form_remote_tag :action => url_for(:controller => :comparisons), :method => :post do = hidden_field_tag :poem1_id, poems[:a].id = hidden_field_tag :poem2_id, poems[:b].id = hidden_field_tag :response, 1 = submit_tag "Vote for me", :disabled => false, :disable_with => 'Vote for me', :class => "compare" .span-4.append-3.last - form_remote_tag :action => url_for(:controller => :comparisons), :method => :post do = hidden_field_tag :poem1_id, poems[:a].id = hidden_field_tag :poem2_id, poems[:b].id = hidden_field_tag :response, 2 = submit_tag "Vote for me", :disable_with => 'Vote for me', :class => "compare" .span-4.prepend-8.append-8.prepend-top.last - form_remote_tag :action => url_for(:controller => :comparisons), :method => :post do = hidden_field_tag :poem1_id, poems[:a].id = hidden_field_tag :poem2_id, poems[:b].id = hidden_field_tag :response, 'draw' = submit_tag "Declare Draw", :disable_with => 'Declare Draw', :class => "compare" RJS page.replace_html :comparison, :partial => 'poems', :object => @poems page.insert_html :top, :previous, :partial => 'comparison', :object => @comparison page << "Effect.ScrollTo($('top'));"

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• How do I choose what and when to cache data with ob_start rather than query the database?

  - by Tim Santeford

  I have a home page that has several independent dynamic parts. The parts consist of a list of recent news from the company, a site statistics panel, and the online status of certain employees. The recent news changes monthly, site statistics change daily, and online statuses change on a per minute bases. I would like to cache these panels so that the db is not hit on every page load. Is using ob_start() then ob_get_contents() to cache these parts to a file the correct way to do this or is there a better method in PHP5 for doing this? In asking this question I'm trying to answer these additional questions: How can I determine the correct approach for caching this data without doing extensive benchmarking? Does it make sense to cache these parts in different files and then join them together per requests or should I re-query the data and cache once per minute? I'm looking for a rule of thumb for planning pages and for situations where doing testing is not cost effective (The client is not paying enough for it I mean). Thanks!

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• Database (and ORM) choice for an small-medium size .NET Application

  - by jim

  I have a requirement to develop a .NET-based application whose data requirements are likely to exceed the 4 gig limit of SQL 2005 Express Edition. There may be other customers of the same application (in the future) with a requirement to use a specific DB platform (such as Oracle or SQL Server) due to in-house DBA expertise. Questions What RDBMS would you guys recommend? From the looks of it the major choices are PostGreSQL, MySQL or FireBird. I've only got experience of MYSQL from these. Which ORM tool (if any) would you recommend using - ideally one that can be swapped out between DB platforms with minimal effort? I like the look of the entity framework but unsure as to the degree to which platforms other than SQL Server are supported. If it helps, we'll be using the 3.5 version of the Framework. I'm open to the idea of using a tool such as NHibernate. On the other hand, if it's going to be easier, I'm happy to write my own stored procedures / DAL code - there won't be that many tables (perhaps 30-35).

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• progressbar not updating binding

  - by BoteRock

  I am trying to make a progress bar that updates when a property value changes I have followed other questions but i don't know what is wrong with it. This is XAML code: <Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:local="clr-namespace:WpfApplication1" x:Class="WpfApplication1.MainWindow" Title="MainWindow"> <Grid Margin="0,0,-8,1"> <ProgressBar Value="{Binding Progreso, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type local:MainWindow}}}" Margin="105,95,207,350"/> <Button Content="Button" Click="Button_Click" Margin="218,232,333,217"/> </Grid> </Window> it is basically a progress bar with the binding and a button with a listener that increases Progreso by 10 this is the C# code: public partial class MainWindow : Window { public MainWindow() { InitializeComponent(); } public event PropertyChangedEventHandler PropertyChanged; protected void NotifyPropertyChanged(string sProp) { if (PropertyChanged != null) { PropertyChanged(this, new PropertyChangedEventArgs(sProp)); } } float progreso = 10; public float Progreso { get { return progreso; } set { progreso = value; NotifyPropertyChanged("Progreso"); } } private void Button_Click(object sender, RoutedEventArgs e) { this.Progreso = this.Progreso + 10; } } I tried to keep it simple but I couldn't get it to work, any help with this would be appreciated. edit: I've also tried UpdateSourceTrigger=PropertyChanged and that didn't work either

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• Velocity CTP: can we 'search' for objects?

  - by Stato Machino

  It appears that 'tags' allow us to associate a 'search term' with the objects placed into the Velocity cache space. However, these can only be queried within a 'region'. Further, regions somehow limit the locality of objects in the cache to a single server (or maybe something kinda like that). So this appears to make it hard to perform any operation for which the unique Id of the cached item is not persisted or continuously available to the application that stores and retrieves objects to and from the cache. In any case, I can't see an easy way to 'cleanse' the cache of objects or to find objects across the entire cache that may share some prefix, postfix or infix values in the cache key so that i can clear out the cache of object repeatedly created in unit tests, for example. And I am unsure about the consequences of regions being associated with single server cache locations. So I would appreciate any help with the following questions: What is the difference between a 'distributed cache' (called a 'partitioned' cache??) when using regions, and a 'local cache'? 1.a. In particular, are the region-oriented values in a distributed cache visible through a cache factory that is configured to 'see' the entire cache space? Are the operations of creating and removing 'regions' efficient enough that it would be reasonable to create a region and a group of tags for each bundle of objects that need to be cached? 2.a. Or does this just push the problem of scoping the 'search for objects' up the chain because the ability of the DataCache object to query down through regions and tags as limited as querying for the cache keys of objects themselves. Thanks, Stato

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• Senior programming 'guru' who can't program - should I find a different career?

  - by confess

  Background: According to my resume I'm supposed to be pretty good at programming. I've worked on a ton of big projects at big companies over many years. When I go for an interview and someone looks at my resume they immediately assume I really know what I'm talking about. I generally communicate well, present myself well, know the 'jargon' and know a lot about technology at a high level, which makes matters worse because after talking to me for a while an interviewer really believes that what my resume says is probably true. The Problem: The problem arises when someone asks me to code something. I choke. As a programmer I have almost no capacity to come up with creative solutions of my own. I can't think through solutions to a programming problem the way good programmers are usually able to. I read questions on StackOverflow and the answer is obvious to me after I read other people's answers but if I am the first person to look at a question with no hints from anyone else I usually don't know where to start. At work it's the same thing. I'm fine if I'm correcting other people's code. I can identify the source of a bug quicker than anyone I work with. But if you ask me to sit down and code up a new application from scratch I will spend ten times longer than programmers who are much more junior than me. Question: Now that I am looking for work this is raising its ugly head in interview situations and making me feel desperately that I'm in the wrong career. I don't know if this problem is incompetence, laziness or some combination of these. Does anyone have any ideas about what I might be dealing with - are there books or exercises that could help me with this basic problem?

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• C++ traits question

  - by duli

  I have a templated class template <typename Data> class C { ..... } In most situations, I depend on the compiler to let me substitute types for Data. I call methods foo(), goo() on objects of type Data, so what I substitute needs to provide that. I now need to substitute int and string for my Data type. I do not want to specialize because the class is already too big and would require specializing each method (with only small code change). My options (please tell me if there are more) 1) I can provide wrapper classes around int and string which implement the methods foo(), goo() etc 2) provide a traits class traits that calls foo() or goo() on objects of classes that provide foo(),goo() (these are my present substitutable classes) and specialize these classes for int and string. Questions 1) what are the relative merits of 1 vs 2? 2) My traits classes will have static methods. Can a traits class have non-static methods as well? I see most traits classes define constants in the STL. 3) Do I make the traits classes global or should I pass them in as a template parameter for class C?

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• What is causing this template-related compile error? (c++)

  - by Setien

  When I try to compile this: #include <map> #include <string> template <class T> class ZUniquePool { typedef std::map< int, T* > ZObjectMap; ZObjectMap m_objects; public: T * Get( int id ) { ZObjectMap::const_iterator it = m_objects.find( id ); if( it == m_objects.end() ) { T * p = new T; m_objects[ id ] = p; return p; } return m_objects[ id ]; } }; int main( int argc, char * args ) { ZUniquePool< std::string > pool; return 0; } I get this: main.cpp: In member function ‘T* ZUniquePool<T>::Get(int)’: main.cpp:12: error: expected `;' before ‘it’ main.cpp:13: error: ‘it’ was not declared in this scope I'm using GCC 4.2.1 on Mac OS X. It works in VS2008. I'm wondering whether it might be a variation of this problem: http://stackoverflow.com/questions/1364837/why-doesnt-this-c-template-code-compile But as my error output is only partially similar, and my code works in VS2008, I am not sure. Can anyone shed some light on what I am doing wrong?

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• Is this a good way to generically deserialize objects?

  - by Damien Wildfire

  I have a stream onto which serialized objects representing messages are dumped periodically. The objects are one of a very limited number of types, and other than the actual sequence of bytes that arrives, I have no way of knowing what type of message it is. I would like to simply try to deserialize it as an object of a particular type, and if an exception is thrown, try again with the next type. I have an interface that looks like this: public interface IMessageHandler<T> where T : class, IMessage { T Handle(string message); } // elsewhere: // (These are all xsd.exe-generated classes from an XML schema.) public class AppleMessage : IMessage { ... } public class BananaMessage : IMessage { ... } public class CoconutMessage : IMessage { ... } Then I wrote a GenericHandler<T> that looks like this: public class GenericHandler<T> : IMessageHandler<T> where T: class, IMessage { public class MessageHandler : IMessageHandler { T IMessageHandler.Handle(string message) { T result = default(T); try { // This utility method tries to deserialize the object with an // XmlSerializer as if it were an object of type T. result = Utils.SerializationHelper.Deserialize<T>(message); } catch (InvalidCastException e) { result = default(T); } return result; } } } Two questions: Using my GenericHandler<T> (or something similar to it), I'd now like to populate a collection with handlers that each handle a different type. Then I want to invoke each handler's Handle method on a particular message to see if it can be deserialized. If I get a null result, move onto the next handler; otherwise, the message has been deserialized. Can this be done? Is there a better way to deserialize data of unknown (but restricted) type?

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• Why is function's length information of other shared lib in ELF?

  - by minastaros

  Our project (C++, Linux, gcc, PowerPC) consists of several shared libraries. When releasing a new version of the package, only those libs should change whose source code was actually affected. With "change" I mean absolute binary identity (the checksum over the file is compared. Different checksum - different version according to the policy). (I should mention that the whole project is always built at once, no matter if any code has changed or not per library). Usually this can by achieved by hiding private parts of the included Header files and not changing the public ones. However, there was a case where just a delete was added to the destructor of a class TableManager (in the TableManager.cpp file!) of library libTableManager.so, and yet the binary/checksum of library libB.so (which uses class TableManager ) has changed. TableManager.h: class TableManager { public: TableManager(); ~TableManager(); private: int* myPtr; } TableManager.cpp: TableManager::~TableManager() { doSomeCleanup(); delete myPtr; // this delete has been added } By inspecting libB.so with readelf --all libB.so, looking at the .dynsym section, it turned out that the length of all functions, even the dynamically used ones from other libraries, are stored in libB! It looks like this (length is the 668 in the 3rd column): 527: 00000000 668 FUNC GLOBAL DEFAULT UND _ZN12TableManagerD1Ev So my questions are: Why is the length of a function actually stored in the client lib? Wouldn't a start address be sufficient? Can this be suppressed somehow when compiling/linking of libB.so (kind of "stripping")? We would really like to reduce this degree of dependency...

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