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  • Preprocessor "macro function" vs. function pointer - best practice?

    - by Dustin
    I recently started a small personal project (RGB value to BGR value conversion program) in C, and I realised that a function that converts from RGB to BGR can not only perform the conversion but also the inversion. Obviously that means I don't really need two functions rgb2bgr and bgr2rgb. However, does it matter whether I use a function pointer instead of a macro? For example: int rgb2bgr (const int rgb); /* * Should I do this because it allows the compiler to issue * appropriate error messages using the proper function name, * not to mention possible debugging benefits? */ int (*bgr2rgb) (const int bgr) = rgb2bgr; /* * Or should I do this since it is merely a convenience * and they're really the same function anyway? */ #define bgr2rgb(bgr) (rgb2bgr (bgr)) I'm not necessarily looking for a change in execution efficiency as it's more of a subjective question out of curiosity. I am well aware of the fact that type safety is neither lost nor gained using either method. Would the function pointer merely be a convenience or are there more practical benefits to be gained of which I am unaware?

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  • Prims vs Polys: what are the pros and cons of each?

    - by Richard Inglis
    I've noticed that most 3d gaming/rendering environments represent solids as a mesh of (usually triangular) 3d polygons. However some examples, such as Second Life, or PovRay use solids built from a set of 3d primitives (cube, sphere, cone, torus etc) on which various operations can be performed to create more complex shapes. So my question is: why choose one method over the other for representing 3d data? I can see there might be benefits for complex ray-tracing operations to be able to describe a surface as a single mathematical function (like PovRay does), but SL surely isn't attempting anything so ambitious with their rendering engine. Equally, I can imagine it might be more bandwidth-efficient to serve descriptions of generalised solids instead of arbitrary meshes, but is it really worth the downside that SL suffers from (ie modelling stuff is really hard, and usually the results are ugly) - was this just a bad decision made early in SL's development that they're now stuck with? Or is it an artefact of what's easiest to implement in OpenGL?

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  • C++ inheritance and member function pointers

    - by smh
    In C++, can member function pointers be used to point to derived (or even base) class members? EDIT: Perhaps an example will help. Suppose we have a hierarchy of three classes X, Y, Z in order of inheritance. Y therefore has a base class X and a derived class Z. Now we can define a member function pointer p for class Y. This is written as: void (Y::*p)(); (For simplicity, I'll assume we're only interested in functions with the signature void f() ) This pointer p can now be used to point to member functions of class Y. This question (two questions, really) is then: Can p be used to point to a function in the derived class Z? Can p be used to point to a function in the base class X?

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  • Do you use an exception class in your Perl programs? Why or why not?

    - by daotoad
    I've got a bunch of questions about how people use exceptions in Perl. I've included some background notes on exceptions, skip this if you want, but please take a moment to read the questions and respond to them. Thanks. Background on Perl Exceptions Perl has a very basic built-in exception system that provides a spring-board for more sophisticated usage. For example die "I ate a bug.\n"; throws an exception with a string assigned to $@. You can also throw an object, instead of a string: die BadBug->new('I ate a bug.'); You can even install a signal handler to catch the SIGDIE psuedo-signal. Here's a handler that rethrows exceptions as objects if they aren't already. $SIG{__DIE__} = sub { my $e = shift; $e = ExceptionObject->new( $e ) unless blessed $e; die $e; } This pattern is used in a number of CPAN modules. but perlvar says: Due to an implementation glitch, the $SIG{DIE} hook is called even inside an eval(). Do not use this to rewrite a pending exception in $@ , or as a bizarre substitute for overriding CORE::GLOBAL::die() . This strange action at a distance may be fixed in a future release so that $SIG{DIE} is only called if your program is about to exit, as was the original intent. Any other use is deprecated. So now I wonder if objectifying exceptions in sigdie is evil. The Questions Do you use exception objects? If so, which one and why? If not, why not? If you don't use exception objects, what would entice you to use them? If you do use exception objects, what do you hate about them, and what could be better? Is objectifying exceptions in the DIE handler a bad idea? Where should I objectify my exceptions? In my eval{} wrapper? In a sigdie handler? Are there any papers, articles or other resources on exceptions in general and in Perl that you find useful or enlightening.

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  • VS2010 possible to convert projects back to VS2008?

    - by JL
    As you all know the VS 2010 RC is out for MSDN subcribers. Unfortunately I guess I have the same problem as some of you, in that the company I work for wants to continue keeping our projects on VS 2008. I would like to know if its possible for me to work with VS 21010, then later convert my projects back to VS2008? I intend to use v3 of the framework for this particular project. Thanks in advance..

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  • possible to get table columns to auto width to fill screen?

    - by Haroldo
    I'd like to have the width of my table 100% of screen width - so flexible to different screen sizes. is it possible to have my columns automatically resize proportionately? I've tried give the td's percentage widths but this doesnt seem to work, firebug shows that the tbody isnt filling the tables width? <table class=""> <tr class="headings"> <td class="entry"> </td> <td class="calendar">Availability Calendar </td> <td class="deals">Last Minute Deals </td> <td class="ann">Announcements </td> <td class="banners">Banners </td> </tr> </table>

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  • Passing dependent objects to a parent constructor in Scala

    - by Nick Johnson
    Suppose I have the following class heirarchy: class A() class B(a:A) class C(b:B) class BaseClass(b:B, c:C) Now I want to implement a subclass of BaseClass, which is given an instance of A, and constructs instances of B and C, which it passes to its superclass constructor. If I could use arbitrary expressions, I'd do something like this: b = new B(a) c = new C(b) super(b, c) Because the second argument to the parent constructor depends on the value of the first argument, though, I can't see any way to do this, without using a factory function, or a gratuitous hack, such as : class IntermediateSubclass(b:B) extends BaseClass(b, new C(b)) class RealSubclass(a:A) extends IntermediateSubclass(new B(a)) Is there clean way to do this?

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  • LaTeX - Changing the font size for a document, but in the preamble, not the document class?

    - by Rory
    I have a LaTeX document. I want to change the font size of all the text, to make it smaller. Normally I would just change the documentclass part. However I am generating LaTeX files from another programme, and it is setting the documentclass, I can't change that. However I can put things in the preamble. Is there anyway to change the font size in the preamble, without touching the documentclass declaration.

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  • How to truly remove all references from VS 2008 project?

    - by Clint
    I have a Visual Studio 2008 project that has a reference to a dll. I removed the reference to version 1 and added a new reference to version 2. The project builds successfully, however when I analyze the project dll after it has been built in Reflector I am seeing that it is holding onto two references to the same dll - version 1 and version 2 are both referenced.

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  • How do HTTP proxy caches decide between serving identity- vs. gzip-encoded resources?

    - by mrclay
    An HTTP server uses content-negotiation to serve a single URL identity- or gzip-encoded based on the client's Accept-Encoding header. Now say we have a proxy cache like squid between clients and the httpd. If the proxy has cached both encodings of a URL, how does it determine which to serve? The non-gzip instance (not originally served with Vary) can be served to any client, but the encoded instances (having Vary: Accept-Encoding) can only be sent to a clients with the identical Accept-Encoding header value as was used in the original request. E.g. Opera sends "deflate, gzip, x-gzip, identity, *;q=0" but IE8 sends "gzip, deflate". According to the spec, then, caches shouldn't share content-encoded caches between the two browsers. Is this true?

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  • emacs/Python: running python-shell in line buffered vs. block buffered mode

    - by Begbie00
    Hi all - In a related question and answer here, someone hypothesized that python-shell within emacs(23.2) was block-buffered instead of line-buffered. The recommended fix was to add sys.stdout.flush() to the spot in my script where I want stdio to flush its contents to the python-shell. Is there someway to trick python-shell (running in emacs 23.2 on Windows, not Linux) into either a) thinking it's attached to a TTY or b) using line-buffered instead of block-buffered mode? I don't see why I'd be able to do this in IDLE but not emacs. I'd rather customize emacs than add sys.stdout.flush() throughout my scripts. Call me lazy :-). Thanks, Mike

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  • error: polymorphic expression with default arguments

    - by 0__
    This following bugs me: trait Foo[ A ] class Bar[ A ]( set: Set[ Foo[ A ]] = Set.empty ) This yields <console>:8: error: polymorphic expression cannot be instantiated to expected type; found : [A]scala.collection.immutable.Set[A] required: Set[Foo[?]] class Bar[ A ]( set: Set[ Foo[ A ]] = Set.empty ) ^ It is quite annoying that I have to repeat the type parameter in Set.empty. Why does the type inference fail with this default argument? The following works: class Bar[ A ]( set: Set[ Foo[ A ]] = { Set.empty: Set[ Foo[ A ]]}) Please note that this has nothing to do with Set in particular: case class Hallo[ A ]() class Bar[ A ]( hallo: Hallo[ A ] = Hallo.apply ) // nope Strangely not only this works: class Bar[ A ]( hallo: Hallo[ A ] = Hallo.apply[ A ]) ...but also this: class Bar[ A ]( hallo: Hallo[ A ] = Hallo() ) // ???

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  • Success function not being called when form is submitted

    - by Tom Hartman
    Hi, I've been trying to figure out why the following script's success function isn't running. Everything in my form works perfectly, and the form contents are being emailed correctly, but the success function isn't being called. If anyone could review my code and let me know why my success function isn't being called I would very much appreciate it! Here is the HTML form with notification divs, which are hidden via css: <div id="success" class="notification"> <p>Thank you! Your message has been sent.</p> </div> <div id="failure" class="notification"> <p>Sorry, your message could not be sent.</p> </div> <form id="contact-form" method="post" action="" class="jqtransform"> <label for="name">Name:</label> <input name="name" id="name" type="text" class="validate[required] input" /> <label for="company">Company:</label> <input name="company" id="company" type="text" class="input" /> <label for="phone">Phone:</label> <input name="phone" id="phone" type="text" class="input" /> <label for="email">Email:</label> <input name="email" id="email" type="text" class="validate[required,email] input" /> <div class="sep"></div> <label for="subject">Subject:</label> <input name="subject" id="subject" type="text" class="validate[required] input" /> <div class="clear"></div> <label for="message">Message:</label> <textarea name="message" id="message" class="validate[required]"></textarea> <div id="check-services"> <input type="checkbox" name="services[]" value="Contractor Recommendation" /> <div>Contractor Recommendation</div> <input type="checkbox" name="services[]" value="Proposal Review" /> <div>Proposal Review</div> <input type="checkbox" name="services[]" value="Existing Website Review" /> <div>Existing Website Review</div> <input type="checkbox" name="services[]" value="Work Evaluation" /> <div>Work Evaluation</div> <input type="checkbox" name="services[]" value="Layman Translation" /> <div>Layman Translation</div> <input type="checkbox" name="services[]" value="Project Management" /> <div>Project Management</div> </div> <div class="sep"></div> <input name="submit" id="submit" type="submit" class="button" value="Send" /> <input name="reset" id="reset" type="reset" class="button" value="Clear" onclick="$.validationEngine.closePrompt('.formError',true)" /> </form> Here is the javascript: // CONTACT FORM VALIDATION AND SUBMISSION $(document).ready(function(){ $('#contact-form').validationEngine({ ajaxSubmit: true, ajaxSubmitFile: 'lib/mail.php', scroll: false, success: function(){ $('#success').slideDown(); }, failure: function(){ $('#failure').slideDown(); $('.formError').animate({ marginTop: '+30px' }); } }); }); And here is my PHP mailer script: <?php $name = $_POST['name']; $company = $_POST['company']; $phone = $_POST['phone']; $email = $_POST['email']; $subject = $_POST['subject']; $message = $_POST['message']; $services = $_POST['services']; $to = '[email protected]'; $subject = 'THC - Contact'; $content .= "You received a message from ".$name.".\r\n\n"; if ($company): $content .= "They work for ".$company.".\r\n\n"; endif; $content .= "Here's the message:\r\n\n".$message."\r\n\n"; $content .= "And they are interested in the services below:\r\n\n"; $content .= implode("\r\n",$services); if ($phone): $content .= "\r\n\nYou can reach them at ".$phone."."; else: $content .= "\r\n\nNo phone number was provided."; endif; $headers = "From: ".$name."\r\n"; $headers .= "Reply-To: ".$email."\r\n"; if (mail($to,$subject,$content,$headers)): return true; else: return false; endif; ?>

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  • Support clicking a link, but sending a POST (vs GET) to the server, without Ajax?

    - by xyld
    I'm thinking this isn't exactly possible, but maybe I'm wrong. I'm simply torn between those who believe that only POST requests should modify data on the server and people that relax the rule and allow GET requests to modify data. Take this situation. Say you have a table, each row is a row in the database. I'd like to allow them to delete the row via a fancy "X" icon as the very last <td></td> element in the row. AFAIK, the only way to send a POST to the server is via a form. But do I really stuff an entire form into the last <td></td> element just to do a POST? Or should I cheat and use an <a href=...></a> tag that sends a GET request? You may be thinking "Do both! Send a POST AND use the <a ...></a> tag! Use fancy javascript + xhr!" And I'll say, oh? And how will that degrade in a zero javascript environment? Maybe we've reached a point when it doesn't make sense to worry about gracefully degrading? I'm not sure. You tell me? I'm new to web development, but I understand most of the concepts involved.

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