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  • c++ class member functions instatiated by traits

    - by Jive Dadson
    I am reluctant to say I can't figure this out, but I can't figure this out. I've googled and searched stackoverflow, and come up empty. The abstract, and possibly overly vague form of the question is, how can I use the traits-pattern to instantiate non-virtual member functions? The question came up while modernizing a set of multivariate function optimizers that I wrote more than 10 years ago. The optimizers all operate by selecting a straight-line path through the parameter space away from the current best point (the "update"), then finding a better point on that line (the "line search"), then testing for the "done" condition, and if not done, iterating. There are different methods for doing the update, the line-search, and conceivably for the done test, and other things. Mix and match. Different update formulae require different state-variable data. For example, the LMQN update requires a vector, and the BFGS update requires a matrix. If evaluating gradients is cheap, the line-search should do so. If not, it should use function evaluations only. Some methods require more accurate line-searches than others. Those are just some examples. The original version instantiates several of the combinations by means of virtual functions. Some traits are selected by setting mode bits that are tested at runtime. Yuck. It would be trivial to define the traits with #define's and the member functions with #ifdef's and macros. But that's so twenty years ago. It bugs me that I cannot figure out a whiz-bang modern way. If there were only one trait that varied, I could use the curiously recurring template pattern. But I see no way to extend that to arbitrary combinations of traits. I tried doing it using boost::enable_if, etc.. The specialized state info was easy. I managed to get the functions done, but only by resorting to non-friend external functions that have the this-pointer as a parameter. I never even figured out how to make the functions friends, much less member functions. The compiler (vc++ 2008) always complained that things didn't match. I would yell, "SFINAE, you moron!" but the moron is probably me. Perhaps tag-dispatch is the key. I haven't gotten very deeply into that. Surely it's possible, right? If so, what is best practice?

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  • Can Ejabberd Support Offline File Transfer?

    - by user359277
    Hi, I am working on a xmpp client, using eJabberd as server. My question is How can I support offline file transferring? I only want to do the offline file transferring for Image file. For example, I can transfer an image to John even he is offline. When John come back Online, the server will send him the image. How can I do that? Thanks

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  • Stick with MFC or go to .Net

    - by Jon Drnek
    We have a largish MFC app that is our main product. This app is being actively developed and there are no plans to stop development. I am new to windows development, but I get the impression that MFC is dead and all the new growth and enhancements are in .net. Is this view accurate? What criteria should we consider when deciding if we should convert this application to .net. Here I'm asking why. I have asked the how question here

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  • dynamic, How to test if a property is available

    - by Miau
    Scenario is very simple somewhere in the code I have this dynamic myVariable = GetDataThatLooksVerySimilarButNotTheSame(); //how to do this? if (myVariable.MyProperty.Exists) //Do stuff So basically the question is how to check (avoiding exceptions) that a certain property is available in my dynamic variable. I could do GetType() but I d rather avoid that, I dont actually want to know the type of the object I want to know if a property (or method if that makes life easier) is available Any pointers? Cheers

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  • How to monitor delayed_job with monit

    - by Luke Francl
    Are there any examples on the web of how to monitor delayed_job with Monit? Everything I can find uses God, but I refuse to use God since long running processes in Ruby generally suck. (The most current post in the God mailing list? God Memory Usage Grows Steadily.) Update: delayed_job now comes with a sample monit config based on this question.

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  • Working with utf-8 files in Eclipse.

    - by Pablo Cabrera
    Quite straight forward question. Is there a way to configure Eclipse to work with text files encoded with utf-8 with and without the BOM? So far I've used eclipse with utf-8 encoding and it works, but when I try to edit a file generated by another editor that includes the BOM, Eclipse doesn't handle it properly, it 'shows an invisible character' at the begining of the file (the BOM). Is there a way to make Eclipse understand utf-8 encoded files with BOM?

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  • Wordpress custom query pagination

    - by Uffo
    I have a wordpress site, where on the main page I list the content from more categories. My question is, is there a plugin where I can paginate the results from a category?I mean something like $this-plugin_paginate('category_id'); or smth? Best Regards,

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  • cocoa -- What is the proper way to tell an NSWindow to redisplay its contents?

    - by William Jockusch
    According to the NSWindow Class Reference, you should "rarely need to invoke" the NSWindow methods "display" or "setViewsNeedDisplay". So what is the usual way to redisplay the window's contents? EDIT: I am having trouble dealing with resizing events. I just want to have everything scale proportionally. See this question. As no one seems to have any ideas for using masks to get it to happen, I want to redraw the whole thing.

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  • Why do so many wpf controls implement CLR properties instead of dependency properties ?

    - by msfanboy
    Hello, is it because the controls programmers are lazy, too hard to implement or not knowledgeable? Wether they are custom controls from 3rd party vendors or Microsoft itself, very much controls have often clr properties instead of DP. Result is I can not bind to them and is wpf not all about binding? :/ My next side question would be, why do so many wpf controls offer visual parts but they are not member of the visual tree ? see wpf datagrid columns, headers... What do you think?

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  • how to make Xcode indentation from beginning of previous line?

    - by Mikkel
    ok, possibly insanely n00b question or something i have overlooked in Xcode prefs: On pressing return, in stead of Xcode's syntax-aware indentation doing smart indent from whatever brackets i've used on the previous line, how can I make it so Xcode indents just from the beginning of the previous line? From the picture below, first block of code is what i got, second block of code is what I want. Visual representation:

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  • Not sure how to use ccTouchesBegan to do what I want it to do.

    - by thyrgle
    So when I see ccTouchesBegan (or touchesBegan for that fact of the matter) I see something like this usually: - (void)ccTouchesBegan:(NSSet*)touches withEvent:(UIEvent*)event { UITouch* touch = [touches anyObject]; } But, what I am not getting is how do you just detect if one object has been touched? For example how would I check if a specific CCSprite I declared has been touched? Sorry if this is a newbish question but, I just don't understand and if you need more clarification just ask how I can clarify myself more.

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  • What are the best authentication and authorization examples for your favorite web framework?

    - by Nathan Feger
    I have been looking through java web frameworks lately (though this question need not be limited to java), and I noticed that most examples on web framework websites leave out auth & auth examples in their stock documentation. one ruby example: acts_as_authenticated (link?) grails has: http://www.grails.org/Authentication+Plugin Anyway, please throw up some links to your framework of choice, and a link to a nice walkthrough to implementing an auth&auth solution.

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  • How to convert from EBCDIC to ASCII in C#.net

    - by Sai
    I have a value in EBCDIC format "000000{". I want to convert it into a.Net Int32 type. Can anyone let me know what I can do about it?? So my question is given a string that contains a signed numeric in EBCDIC , what should I be doing to convert it into a .NET Int32. Thanks so much in advance!

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  • Approach for authentication and storing user details.

    - by cappuccino
    Hey folks, I am using the Zend Framework but my question is broadly about sessions / databases / auth (PHP MySQL). Currently this is my approach to authentication: 1) User signs in, the details are checked in database. - Standard stuff really. 2) If the details are correct only the user's unique ID is stored in the session and a security token (user unique ID + IP + Browser info + salt). The session in written to the filesystem. I've been reading around and many are saying that storing stuff in sessions is not a good idea, and that you should really only write a unique ID which refers back to the user's details and a security token to prevent session hijacking. So this is the approach i've taken, i use to write the user's details in session, but i've moved that out. Wanted to know your opinions on this. I'm keeping sessions in the filesystem since i don't run on multiple servers, and since i'm only writting a tiny tiny bit of data to sessions, i thought that performance would be greater keeping sessions in the filesystem to reduce load on the database. Once the session is written on authentication, it really is only read-only from then on. 3) The rest of the user's details (like subscription details, permissions, account info etc) are cached in the filesystem (this can always be easily moved to memory if i wanted even more performance). So rather than keeping the user's details in session, the user's details are cached in the file system. I'm using Zend_Cache and the unique cache id is something like md5(/cache/auth/2892), the number is the unique id of the user. I guess the benefit of this method is that once the user is logged in, there is essentially not database queries being run to get the user's details. Just wonder if this approach is better than keeping the whole lot in session... 4) As the user moves throughout the site the only thing that is checked is the ID in the session and the security token. So, overall the first question is 1) is the filesystem more efficient than a database for this purpose 2) have i taken enough security precautions 3) is separating user detail's from the session into a cached file a pointless task? Thanks.

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  • Is there a recommended approach to handle saving data in response to within-site navigation without

    - by Carvell Fenton
    Hello all, Preamble to scope my question: I have a web app (or site, this is an internal LAN site) that uses jQuery and AJAX extensively to dynamically load the content section of the UI in the browser. A user navigates the app using a navigation menu. Clicking an item in the navigation menu makes an AJAX call to php, and php then returns the content that is used to populate the central content section. One of the pages served back by php has a table form, set up like a spreadsheet, that the user enters values into. This table is always kept in sync with data in the database. So, when the table is created, is it populated with the relevant database data. Then when the user makes a change in a "cell", that change immediately is written back to the database so the table and database are always in sync. This approach was take to reassure users that the data they entered has been saved (long story...), and to alleviate them from having to click a save button of some kind. So, this always in sync idea is great, except that a user can enter a value in a cell, not take focus out of the cell, and then take any number of actions that would cause that last value to be lost: e.g. navigate to another section of the site via the navigation menu, log out of the app, close the browser, etc. End of preamble, on to the issue: I initially thought that wasn't a problem, because I would just track what data was "dirty" or not saved, and then in the onunload event I would do a final write to the database. Herein lies the rub: because of my clever (or not so clever, not sure) use of AJAX and dynamically loading the content section, the user never actually leaves the original url, or page, when the above actions are taken, with the exception of closing the browser. Therefore, the onunload event does not fire, and I am back to losing the last data again. My question, is there a recommended way to handle figuring out if a person is navigating away from a "section" of your app when content is dynamically loaded this way? I can come up with a solution I think, that involves globals and tracking the currently viewed page, but I thought I would check if there might be a more elegant solution out there, or a change I could make in my design, that would make this work. Thanks in advance as always!

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