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• Ways not to write function headers twice?

  - by mee

  Hi, I've got a C/C++ question, can I reuse functions across different object files or projects without writing the function headers twice? (one for defining the function and one for declaring it) I don't know much about C/C++, Delphi and D. I assume that in Delphi or D, you would just write once what arguments a function takes and then you can use the function across diferent projects. And in C you need the function declaration in header files *again??, right?. Is there a good tool that will create header files from C sources? I've got one, but it's not preprocessor-aware and not very strict. And I've had some macro technique that worked rather bad. I'm looking for ways to program in C/C++ like described here http://www.digitalmars.com/d/1.0/pretod.html

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• Dll only loads correctly via LoadLibrary?

  - by Steve

  I'm trying to use dbghelp.dll. If I set it up in the VS2008 properties to point to the correct library and header file, and put dbghelp.dll in the same directory as the executable, one of the functions in the dll fails. If I LoadLibrary the dll, everything that function works. I've looked at the header that gets included via the VS option, and the right one is being pulled in. The correct lib is being pulled in (checked via /verbose option), and depends.exe shows the correct dll is loaded. Does anyone know why I can't get this to work? I'll probably just go with LoadLibrary, but I'm genuinely stumped on this one. EDIT: SymfromAddr fails with an "error 87", whatever that is. If I load the dll via LoadLibrary, it works.

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• Design pattern: polymorphisim for list of objects

  - by ziang

  Suppose I have a class A, and A1, A2 inherits from A. There are 2 functions: List<A1> getListA1(){...} List<A2> getListA2(){...} Now I want to do something similar to both A1 and A2 in another function public void process(List<A>){...} If I want to pass the instance of either ListA1 or ListA2, of course the types doesn't match because the compiler doesn't allow the coercion from List< A1 to List< A. I can't do something like this: List<A1> listA1 = getListA1(); List<A> newList = (List<A>)listA1; //this is not allowed. So what is the best approach to the process()? Is there any way to do it in a universal way rather than write the similar code to both List and List?

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• C++ Thread Safe Integer

  - by Paul Ridgway

  Hello everyone, I have currently created a C++ class for a thread safe integer which simply stores an integer privately and has public get a set functions which use a boost::mutex to ensure that only one change at a time can be applied to the integer. Is this the most efficient way to do it, I have been informed that mutexes are quite resource intensive? The class is used a lot, very rapidly so it could well be a bottleneck... Googleing C++ Thread Safe Integer returns unclear views and oppinions on the thread safety of integer operations on different architectures. Some say that a 32bit int on a 32bit arch is safe, but 64 on 32 isn't due to 'alignment' Others say it is compiler/OS specific (which I don't doubt). I am using Ubuntu 9.10 on 32 bit machines, some have dual cores and so threads may be executed simultaneously on different cores in some cases and I am using GCC 4.4's g++ compiler. Thanks in advance...

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• Simple Scala syntax - trying to define "==" operator - what am I missing?

  - by Alex R

  While experimenting with some stuff on the REPL, I got to a point where I needed something like this: scala class A(x:Int) { println(x); def ==(a:A) : Boolean = { this.x == a.x; } } Just a simple class with an "==" operator. Why doesn't it work??? Here's the result: :10: error: type mismatch; found : A required: ?{val x: ?} Note that implicit conversions are not applicable because they are ambiguous: both method any2ArrowAssoc in object Predef of type [A](x: A)ArrowAssoc[A] and method any2Ensuring in object Predef of type [A](x: A)Ensuring[A] are possible conversion functions from A to ?{val x: ?} class A(x:Int) { println(x); def ==(a:A) : Boolean = { this.x == a.x; } } ^ This is scala 2.8 RC1. Thanks

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• Converting a stopwatch time to milliseconds (regex)

  - by Nick

  I'm trying to figure out the best way to convert a string containing a time to an integer number of milliseconds. I'm using a suboptimal way using a bunch of preg_match()'s and some array handling, but I was wondering if there was an elegant way. Here are some example stopwatch times (some wouldn't actually be seen on a stopwatch but need to be converted anyway): 3:34:05.81 34:05 5 (just 5 seconds) 89 (89 seconds) 76:05 (76 minutes, 5 seconds) Millseconds will not extend past 2 decimal places. You can give me an example using either PHP or Javascript regex functions. Thanks!

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• exec() function doesn't rule svn checkout

  - by bahamut100

  Hi, I'm writing some functions in php using exec() to interrogate a svn. The commands exec("svn list ".$myurl) works. Now, I try to get a path on a svn repository with the checkout command. When I put the command "svn checkout http://core.wordress.org/tags/2.9.2/ last-version" directly in the console, it works. But when I do this from a php script using exec(), like this : exec("svn checkout ".$myurl, $dir) it doesn't work. Have you an idea ??

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• Is there a way to extract the message from a JavaScript dialog in Chrome?

  - by Samuel

  I’ve been working on an extension for automating tests in Chrome, and I came across an obscure issue with JavaScript dialogs. The message shown in the dialog can’t be readily retrieved/copied. I’ve used the GetWindowText and InternalGetWindowText functions, but they only return the title of the dialog and the text from the buttons, not the actual message itself. I even looked at programs that extract text from forms, but no luck. So does anyone know of a way to retrieve the text from these JavaScript dialogs in Chrome?

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• R: how to make a unique set of names from a vector of strings?

  - by Mike Dewar

  Hi, I have a vector of strings. Check out my vector, it's awesome: > awesome [1] "a" "b" "c" "d" "d" "e" "f" "f" I'd like to make a new vector that is the same length as awesome but where, if necessary, the strings have been uniqueified. For example, a valid output of my desired function would be > awesome.uniqueified [1] "a" "b" "c" "d.1" "d.2" "e" "f.1" "f.2" Is there an easy, R-thonic and beautiful way to do this? I should say my list in real life (it's not called awesome) contains 25000ish mircoarray probeset identifiers. I'm always nervous when I embark on writing little generic functions (which I'm sure I could do) as I'm sure some R guru has come across this problem in the past, nailed it with some incredible algorithm that doesn't even have to store more than half an element in the vector. I'm just not sure what they might have called it. Probably not uniqueify.

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• Is passing a Command object/Reader to a function a good idea?

  - by Cyril Gupta

  I've been getting some inexplicable errors (running out of connections from the connection pool) with MySql database with .Net 4 (C#). Till now all my attempts at finding a reason for this have been in vain. Now I also have a situation in which a lock on a table is not cleared for a long time even though all I have been doing is read operations from it. My code looks okay (I've put all readers and connections in using blocks). The only anomaly I have is that I've been passing MySqlCommand and MySqlDataReader objects as parameters to functions who work with them. That doesn't seem like a bad idea for me because it avoids some repetition (DRY!). But since I can't find any other explanation I have to suspect that this is causing the problem. What do you think?

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• How to maintain fixed size of C variable types over different machines?

  - by Alex

  I've all this kind of functions. ssize_t fuc1(int var1, void *buf, size_t count); int func2(char *charPtr, int mode, int dev); short func3( long var2); problem is that data types in C has different sizes when compiled on different machines(64bit & 32bit). This is true for even void*. For some reasons. I need to ensure that these sizes all are same on every machine(64bit & 32bit). So, how should I modify these ?

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• Can you make a PHP function recursive without repeating it's name?

  - by alex

  It's always bugged me a recursive function needs to name itself, when a instantiated class can use $this and a static method can use self etc. Is there a similar way to do this in a recursive function without naming it again (just to cut down on maintenance)? Obviously I could use call_user_func or the __FUNCTION__ constant but I would prefer something less ugly. Update Thanks for your answers. I might stick to including the function name for simple functions, and make take the other approaches for anything more complicated.

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• What is the Perl equivalent to C's #include? [closed]

  - by Herms

  Possible Duplicate: How do I include functions from another file in my Perl script? I have a couple simple perl scripts that share some subroutines. I'd like to pull those subroutines out into another file, but I'm not sure how to go about doing that. All I need is an equivalent to C's #include. I found a couple things online about creating modules, but that seems like overkill for what I'm doing. Is there a way to just tell perl to load/execute another perl script inline, so it's treated as if it's just part of the file (like #include in C)?

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• OO C++ - Virtual Methods

  - by Phorce

  Just a really quick question here. I'm using virtual functions to read in from a text file. Now, it's virtual because in one aspect I want the values to be normalised, and, in the other respect I don't want them to be normalised. I have tried to do this: bool readwav(string theFile, 'native'); So in theory, if the 'native' is used, this method should be called, however, if 'double' is called then a different version of the method is called. Same for if the value is empty, it should just perform the native option. First question, why doesn't the declaration above work? Also, is this the best route to go down? Or, would it be better to have just one class method that switches between the options. Thanks :)

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• Custom constructors for models in Google App Engine (python)

  - by Nikhil Chelliah

  I'm getting back to programming for Google App Engine and I've found, in old, unused code, instances in which I wrote constructors for models. It seems like a good idea, but there's no mention of it online and I can't test to see if it works. Here's a contrived example, with no error-checking, etc.: class Dog(db.Model): name = db.StringProperty(required=True) breeds = db.StringListProperty() age = db.IntegerProperty(default=0) def __init__(self, name, breed_list, **kwargs): db.Model.__init__(**kwargs) self.name = name self.breeds = breed_list.split() rufus = Dog('Rufus', 'spaniel terrier labrador') rufus.put() The **kwargs are passed on to the Model constructor in case the model is constructed with a specified parent or key_name, or in case other properties (like age) are specified. This constructor differs from the default in that it requires that a name and breed_list be specified (although it can't ensure that they're strings), and it parses breed_list in a way that the default constructor could not. Is this a legitimate form of instantiation, or should I just use functions or static/class methods? And if it works, why aren't custom constructors used more often?

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• IPhone: different system timers??

  - by matt

  I have been using mach_absolute_time() for all my timing functions so far. calculating how long between frames ect. I now want to get the exact time touch input events happen using event.timestamp in the touch callbacks. the problem is these two seem to use completely different timers. sure, you can get them both in seconds, but their origins are different and seemingly random... is there any way to sync the two different timers? or is there anyway to get access to the same timer that the touch input uses to generate that timestamp property? otherwise its next to useless.

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• checksum error with building an HTTP packet(but over TCP, like syn/ack its ok)

  - by Hila

  I am building a NAT program,I change each packet that comes from our internal subnet, change it's source IP address by libnet functions.( catch the packet with libpcap, put it sniff structures and build the new packet with libnet) I am trying to build an http packet. When I look on wireshark, I see that the new packet that I have built is exectly like the original packet(the only diffrent is that I changed the src port and ip), but there is a checksum error, So the server don't do anything with the packet that I have sent to him, beacuse the cheksum field is wrong. When I send a tcp packet(like syn or ack), the checksum is ok, and the server respons. Is anyone knows what can cause this problem? the new checksum in other packets is calculated as it should be.. but in the HTTP packet it doesn't..

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• Whats the API Key for in Google Maps API V3?

  - by Brandon

  In the older version of the API, I'd have to insert the javascript into the page using something like this for just basic functionality to work: http://maps.google.com/maps?file=api&v=2&key=GoogleMapsAPIKey Where I had to configure the API key for each individual site. Looking at the documentation, it says to get a basic map working I just need this: http://maps.google.com/maps/api/js?sensor=true/false Where does the API key fit in? Do I need to worry about it if I just plan on using a basic map and marker and none of the more advanced functions?

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• Using opencv in Win32 application for image show

  - by erjik

  Is it possible to output images so that they all will be inside a single window? Before, I used to output data using only opencv functions: cvNamedWindow("Image 1"); cvShowImage("Image 1", img); So I change image, then call: cvShowImage function and so on. But If I want to look at more than one image, then every new image needs its own window to be shown there And what I want is to put every such an output opencv's window inside one big main window. Is it possible to do it? And how?

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• Unsigneds in order to prevent negative numbers

  - by Bruno Brant

  let's rope I can make this non-sujective Here's the thing: Sometimes, on fixed-typed languages, I restrict input on methods and functions to positive numbers by using the unsigned types, like unsigned int or unsigned double, etc. Most libraries, however, doesn't seem to think that way. Take C# string.Length. It's a integer, even though it can never be negative. Same goes for C/C++: sqrt input is an int or a double. I know there are reasons for this ... for example your argument might be read from a file and (no idea why) you may prefer to send the value directly to the function and check for errors latter (or use a try-catch block). So, I'm assuming that libraries are way better designed than my own code. So what are the reasons against using unsigned numbers to represent positive numbers? It's because of overflow when we cast then back to signed types?

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• Performselector not call in NSThread

  - by abdulsamad

  Hi all, I have a problem that i want to call a function when one of my functions that is running into a seperate thread comes to an end. its like that [NSThread detachNewThreadSelector:@selector(fetchFeaturedFreeApps) toTarget:self withObject:nil]; here is my fetchFeaturedFreeApps function -(void)fetchFeaturedFreeApps { ////all my code [self performSelector:@selector(closeView) withObject:nil afterDelay:4.0]; } My problem is that the close view methods doesnt run after the 4 seconds. Hoew if i call the fetchFeaturedFreeApps method with perform selector then my closeview metod is called properly. Your valuable help is highly appreciated.

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• Preventing Race Conditions

  - by Qua

  I'm using the built-in ajax functionality of MVC2. Basically the user types a search query, and on every key press a set of results for the query is shown. This works fine in almost all cases, but sometimes the server is a bit slow with a single response, and thus the result for the next key stroke is returned before the previous. When the previous key stroke result set is finally returned to the client it will overwrite the results for the newer search query that should actually have been shown. My code follows more or less along these lines: <% using (Ajax.BeginForm("SearchUser", null, new AjaxOptions() { UpdateTargetId = "findUserResults" }, new { id = "findUserAjaxForm" })) {%> Every keystroke submits this form and thus outputs the results in the 'findUserResults' element. How can I prevent older results from being displayed while still making use of the built-in functions provided in MVC2?

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• GNUPlot: plot different ranges with different styles

  - by Mr. Shickadance

  Hello all, I know this should be pretty simple, but I haven't been able to find a similar example. I need to plot different ranges of a datafile differently, but on the same graph. For instance, say my datafile represents a function with x and y values. I want to plot the first N values using a style like lines, and then the next M values using a different style, like points. I was thinking I would need a plot command similar to this: plot [1:5] "my.data" using 1:2 with lines, [6:12] using 1:2 with points, [13:19] using 1:2 with lines Essentially I want to distinguish different areas of the functions. Any ideas? I am sorry if it sounds like I'm rambling but I am quite stumped. Thanks in advance!

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• C/C++ usage of special CPU features

  - by b-gen-jack-o-neill

  Hi, I am curious, do new compilers use some extra features built into new CPUs such as MMX SSE,3DNow! and so? I mean, in original 8086 there was even no FPU, so compiler that old cannot even use it, but new compilers can, since FPU is part of every new CPU. So, does new compilers use new features of CPU? Or, it should be more right to ask, does new C/C++ standart library functions use new features? Thanks for answer.

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• Eclipse + AppEngine =? autocomplete

  - by Brandon Watson

  I was doing some beginner AppEngine dev on a Windows box and installed Eclipse for that. I liked the autocompletion I got with the objects and functions. I moved my dev environment over to my Macbook, and installed Eclipse Ganymede. I installed the AppEngine SDK and Eclipse plug in. However, when I am typing out code now, the autocomplete isn't functioning. Did I miss a step? UPDATE Just to add to this: the line: import cgi appears to give me what I need. When I type "cgi." I get all of the auto complete. However, the lines: from google.appengine.api import users from google.appengine.ext import webapp from google.appengine.ext.webapp.util import run_wsgi_app from google.appengine.ext import db don't give me any auto complete. If I type "users." there is no auto complete.

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