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  • I'm having a problem identifying a floating point exception.

    - by Peter Stewart
    I'm using c++ in visual studio express to generate random expression trees for use in a genetic algorithm type of program. Because they are random, the trees often generate (I'll call them exceptions, I'm not sure what they are) Thanks to a suggestion by George, I turned the mask _MCW_EM on so that hardware interrupts are turned off. (the default) So, the program runs uninterrupted, but some of the values returned are: -1.#INF, -1.#NAN, -1.#INV. I don't know how to identify these so that I can throw an exeption: if ( variable == -1.#INF) ?? DigitalRoss in this post seemed to have the solution, but as I understood it I couldn't make it work. I've been looking all over the place for this simple bit of code, that I assumed would be used all the time, but have had no luck. thanks

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  • Is this a good starting point for iptables in Linux?

    - by sbrattla
    Hi, I'm new to iptables, and i've been trying to put together a firewall which purpose is to protect a web server. The below rules are the ones i've put together so far, and i would like to hear if the rules makes sense - and wether i've left out anything essential? In addition to port 80, i also need to have port 3306 (mysql) and 22 (ssh) open for external connections. Any feedback is highly appreciated! #!/bin/sh # Clear all existing rules. iptables -F # ACCEPT connections for loopback network connection, 127.0.0.1. iptables -A INPUT -i lo -j ACCEPT # ALLOW established traffic iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT # DROP packets that are NEW but does not have the SYN but set. iptables -A INPUT -p tcp ! --syn -m state --state NEW -j DROP # DROP fragmented packets, as there is no way to tell the source and destination ports of such a packet. iptables -A INPUT -f -j DROP # DROP packets with all tcp flags set (XMAS packets). iptables -A INPUT -p tcp --tcp-flags ALL ALL -j DROP # DROP packets with no tcp flags set (NULL packets). iptables -A INPUT -p tcp --tcp-flags ALL NONE -j DROP # ALLOW ssh traffic (and prevent against DoS attacks) iptables -A INPUT -p tcp --dport ssh -m limit --limit 1/s -j ACCEPT # ALLOW http traffic (and prevent against DoS attacks) iptables -A INPUT -p tcp --dport http -m limit --limit 5/s -j ACCEPT # ALLOW mysql traffic (and prevent against DoS attacks) iptables -A INPUT -p tcp --dport mysql -m limit --limit 25/s -j ACCEPT # DROP any other traffic. iptables -A INPUT -j DROP

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  • What's the point of having to provide a cacheName for NSFetchedResultsController?

    - by dontWatchMyProfile
    NSFetchedResultsController *frc = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:moc sectionNameKeyPath:nil cacheName:@"Root"]; Why do we have to think about a cacheName? How important is this decision? What would happen if there are two NSFetchedResultsController instances using the exact same cacheName? Does that matter? Is that some kind of singleton stuff? Thinking about Core Animation, there's also this strange animationID parameter, but setting it to the exact same thing for dozens of simultaneous animations doesn't hurt the animations at all. So I guess it's probably the same thing here...or not?

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  • Android - Get Notified when a new access point is added?

    - by Donal Rafferty
    I was wondering is it possible to get a notification of when a new configured network is added to the WifiManager in Android? I know you can get the current list of configured networks getConfiguredNetworks But is it possible to get notification of when a new one is added? I dont see anything in the WifiManager that would be helpful. Has anyone any other ideas? Or insight into how this could be achieved?

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  • Fastest way to clamp a real (fixed/floating point) value?

    - by Niklas
    Hi, Is there a more efficient way to clamp real numbers than using if statements or ternary operators? I want to do this both for doubles and for a 32-bit fixpoint implementation (16.16). I'm not asking for code that can handle both cases; they will be handled in separate functions. Obviously, I can do something like: double clampedA; double a = calculate(); clampedA = a > MY_MAX ? MY_MAX : a; clampedA = a < MY_MIN ? MY_MIN : a; or double a = calculate(); double clampedA = a; if(clampedA > MY_MAX) clampedA = MY_MAX; else if(clampedA < MY_MIN) clampedA = MY_MIN; The fixpoint version would use functions/macros for comparisons. This is done in a performance-critical part of the code, so I'm looking for an as efficient way to do it as possible (which I suspect would involve bit-manipulation) EDIT: It has to be standard/portable C, platform-specific functionality is not of any interest here. Also, MY_MIN and MY_MAX are the same type as the value I want clamped (doubles in the examples above).

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  • sqrt(int_value + 0.0) ? The point?

    - by Earlz
    Hello, while doing some homework in my very strange C++ book, which I've been told before to throw away, had a very peculiar code segment. I know homework stuff always throws in extra "mystery" to try to confuse you like indenting 2 lines after a single-statement for-loop. But this one I'm confused on because it seems to serve some real-purpose. basically it is like this: int counter=10; ... if(pow(floor(sqrt(counter+0.0)),2) == counter) ... I'm interested in this part especially: sqrt(counter+0.0) Is there some purpose to the +0.0? Is this the poormans way of doing a static cast to a double? Does this avoid some compiler warning on some compiler I do not use? The entire program printed the exact same thing and compiled without warnings on g++ whenever I left out the +0.0 part. Maybe I'm not using a weird enough compiler?

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  • Cannot use String.Empty as a default value for an optional parameter in C# - then what's the point?

    - by Mikeyg36
    I am reading Effective C# by Bill Wagner. In Item 14 - Minimize Duplicate Initialization Logic, he shows the following example of using the new optional parameters feature in a constructor: public MyClass(int initialCount = 0, string name = "") Notice that he used "" instead of string.Empty. He comments: You'll note [in an example above] that the second constructor specified "" for the default value on the name parameter, rather than the more customary string.Empty. That's because string.Empty is not a compile-time constant. It is a static property defined in the string class. Because it is not a compile constant, you cannot use it for the default value for a parameter. If we cannot use the string.Empty static in all situations, then doesn't that defeat the purpose of it? I thought that we would use it to be sure that we have a system-independent means of referring to the empty string. Is my understanding wrong? Thanks.

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  • How do you calculate div and mod of floating point numbers?

    - by boost
    In Perl, the % operator seems to assume integers. For instance: sub foo { my $n1 = shift; my $n2 = shift; print "perl's mod=" . $n1 % $n2, "\n"; my $res = $n1 / $n2; my $t = int($res); print "my div=$t", "\n"; $res = $res - $t; $res = $res * $n2; print "my mod=" . $res . "\n\n"; } foo( 3044.952963, 7.1 ); foo( 3044.952963, -7.1 ); foo( -3044.952963, 7.1 ); foo( -3044.952963, -7.1 ); gives perl's mod=6 my div=428 my mod=6.15296300000033 perl's mod=-1 my div=-428 my mod=6.15296300000033 perl's mod=1 my div=-428 my mod=-6.15296300000033 perl's mod=-6 my div=428 my mod=-6.15296300000033 Now as you can see, I've come up with a "solution" already for calculating div and mod. However, what I don't understand is what effect the sign of each argument should have on the result. Wouldn't the div always be positive, being the number of times n2 fits into n1? How's the arithmetic supposed to work in this situation?

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  • Three Java classes: point out all the issues you can find!

    - by Sicarius
    I wrote three classes for a colleague of mine (I'm new at this job). They compile just fine, but he tells me there are "defects, bugs, and style problems." He wants me to print the files out and mark the problems such as the standard coding conventions, best practices, format, design, and logic. I wrote this code when I was extremely tired and I plan to rewrite it completely. My mistake was showing to it before looking it over myself again. However, he still wants me to do the markings on paper. Any input is greatly appreciated! The three Java classes ['Station.java', 'ParserInt.java', 'ParserException.java'] are uploaded here: http://www.megaupload.com/?d=N2CUVSV2

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  • Classes. Whats the point?

    - by Ben Shelock
    I'm fairly new to OOP in PHP, I've made a couple of basic scripts but nothing impressive. All I've really taken from it is that it would probably be easier just make a collection of functions and include them. The structure of classes seems to just confuse what was otherwise a simple process. And in collating everything into a class it doesn't really add any functionality. So I'm clearly missing something. Could someone explain what functionality is added by creating classes

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  • Should we point to an NSManagedObject entity with weak instead of strong pointer?

    - by Jim Thio
    I think because NSManagedObject is managed by the managedObject context the pointer should be weak. Yet it often goes back to 0 in my cases. for (CategoryNearby * CN in sorted) { //[arrayOfItems addObject:[NSString stringWithFormat:@"%@ - %d",CN.name,[CN.order intValue]]]; NearbyShortcutTVC * tvc=[[NearbyShortcutTVC alloc]init]; tvc.categoryNearby =CN; // tvc.titleString=[NSString stringWithFormat:@"%@",CN.name]; // tvc.displayed=CN.displayed; [arrayOfItemsLocal addObject:tvc]; //CN PO(tvc); PO(tvc.categoryNearby); while (false); } self.arrayOfItems = arrayOfItemsLocal; PO(self.categoriesNearbyInArrayOfItems); [self.tableViewa reloadData]; ... Yet somewhere down the line: tvc.categoryNearby becomes nil. I do not know how or when or where it become nil. How do I debug this? Or should the reference be strong instead? This is the interface of NearbyShortcutTVC by the way @interface NearbyShortcutTVC : BGBaseTableViewCell{ } @property (weak, nonatomic) CategoryNearby * categoryNearby; @end To make sure that we're talking about the same object I print all the memory addresses of the NSArray They're both the exact same object. But somehow the categoryNearby property of the object is magically set to null somewhere. self.categoriesNearbyInArrayOfItems: ( 0x883bfe0, 0x8b6d420, 0x8b6f9f0, 0x8b71de0, 0xb073f90, 0xb061a10, 0xb06a880, 0x8b74940, 0x8b77110, 0x8b794e0, 0x8b7bf40, 0x8b7cef0, 0x8b7f4b0, 0x8b81a30, 0x88622d0, 0x8864e60, 0xb05c9a0 ) self.categoriesNearbyInArrayOfItems: ( 0x883bfe0, 0x8b6d420, 0x8b6f9f0, 0x8b71de0, 0xb073f90, 0xb061a10, 0xb06a880, 0x8b74940, 0x8b77110, 0x8b794e0, 0x8b7bf40, 0x8b7cef0, 0x8b7f4b0, 0x8b81a30, 0x88622d0, 0x8864e60, 0xb05c9a0 )

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  • In .NET, How to obtain the target of a symbolic link (or Reparse Point)?

    - by Cheeso
    In .NET, I think I can determine if a file is a symbolic link by calling System.IO.File.GetAttributes(), and checking for the ReparsePoint bit. like so: var a = System.IO.File.GetAttributes(fileName); if ((a & FileAttributes.ReparsePoint) != 0) { // it's a symlink } How can I obtain the target of the symbolic link, in this case? ps: I know how to create a symbolic link. It requires P/Invoke: [Interop.DllImport("kernel32.dll", EntryPoint="CreateSymbolicLinkW", CharSet=Interop.CharSet.Unicode)] public static extern int CreateSymbolicLink(string lpSymlinkFileName, string lpTargetFileName, int dwFlags);

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  • The correct point in time to read an ASP .NET 1.1 control property in order to change page output

    - by RossMan
    Using ASP .NET 1.1 with CMS 2002 and C#. Trying to read the contents of a CMS HTML placeholder control into a string reader object so certain logic can be performed and the page output modified before it is displayed: StringReader srHtml = new StringReader(this.HtmlPlaceholderControl1.Html); The problem is that the Html property is empty during Page_Load, I've tried in a PreRender overload as well, but the property is still empty. The HtmlPlaceholder control does render html when the page load has completed. Which event should be handled in order to read the propery of the web control?

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  • How do I dynamically point an interface to a specific class at runtime?

    - by Jon
    As a simple example, I have an xml file with a list of names of classes which actually carry out the work and all implement interface IDoWork with a method Process(). I loop through the items in the xml file. How do I actually dynamically assign the class to the interface from a string name? e.g. var IDoWork = new "DoWorkType1"(); IDoWork.Process(); <work> <item id="DoWorkType1"> </item> <item id="DoWorkType2"> </item> </work> I want to achieve a plugin type architecture, except the plugin isn't at an assembly level only a class level within my program.

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  • How to calculate the latlng of a point a certain distance away from another?

    - by Rene Saarsoo
    To draw a circle on map I have a center GLatLng (A) and a radius (r) in meters. Here's a diagram: ----------- --/ \-- -/ \- / \ / \ / r \ | *-------------* \ A / B \ / \ / -\ /- --\ /-- ----------- How to calculate the GLatLng at position B? Assuming that r is parallel to the equator. Getting the radius when A and B is given is trivial using the GLatLng.distanceFrom() method - but doing it the other way around not so. Seems that I need to do some heavier math.

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  • What's the point of the javascript navigator.javaEnabled function?

    - by den shade
    The navigator object has a javaEnabled function that indicates if the browser has javascript support. This seems to be a little odd: If JS is indeed enabled the function will return true, well obviously. If JS is disabled it will return <nothing since it is never run, javaScript is disabled. I must be missing something here, or is it really that useless this function?

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  • How can I convert floating point values in text to binary using Perl?

    - by YoDar
    I have text file looks like that: float a[10] = { 7.100000e+000 , 9.100000e+000 , 2.100000e+000 , 1.100000e+000 , 8.200000e+000 , 7.220000e+000 , 7.220000e+000 , 7.222000e+000 , 1.120000e+000 , 1.987600e+000 }; unsigned int col_ind[10] = { 1 , 4 , 3 , 4 , 5 , 2 , 3 , 4 , 1 , 5 }; Now, I want to convert each array (float / unsigned int) to different binary files - big endian type. Binary file for all float values and binary file for all integer values. What is the simple way to do it in Perl, consider I have over 2 millon elements in each array?

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  • Test for `point` within an attachment in `mail-mode`

    - by lawlist
    I'm looking for a better test to determine when point is within a hidden attachment in mail-mode (which is used by wl-draft-mode). The attachments are mostly hidden and look like this: --[[application/xls Content-Disposition: attachment; filename="hello-world.xls"][base64]] The test of invisible-p yields a result of nil. I am current using the following test, but it seems rather poor: (save-excursion (goto-char (point-max)) (goto-char (previous-char-property-change (point))) (goto-char (previous-char-property-change (point))) (re-search-backward "]]" (point-at-bol) t))) Any suggestions would be greatly appreciated. Here is the full snippet: (goto-char (point-max)) (cond ((= (save-excursion (abs (skip-chars-backward "\n\t"))) 0) (insert "\n\n")) ((and (= (save-excursion (abs (skip-chars-backward "\n\t"))) 1) (not (save-excursion (goto-char (previous-char-property-change (point))) (goto-char (previous-char-property-change (point))) (re-search-backward "]]" (point-at-bol) t)))) (insert "\n"))) GOAL:  If there are no attachments and no new lines at the end of the buffer, then insert \n\n and then insert the attachment thereafter. If there is just one new line at the end of the buffer, then insert \n and then insert the attachment thereafter. If there is an attachment at the end of the buffer, then do not insert any new lines.

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