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  • 0xDEADBEEF equivalent for 64-bit development?

    - by Peter Mortensen
    For C++ development for 32-bit systems (be it Linux, Mac OS or Windows, PowerPC or x86) I have initialised pointers that would otherwise be undefined (e.g. they can not immediately get a proper value) like so: int *pInt = reinterpret_cast<int *>(0xDEADBEEF); (To save typing and being DRY the right-hand side would normally be in a constant, e.g. BAD_PTR.) If pInt is dereferenced before it gets a proper value then it will crash immediately on most systems (instead of crashing much later when some memory is overwritten or going into a very long loop). Of course the behavior is dependent on the underlying hardware (getting a 4 byte integer from the odd address 0xDEADBEEF from a user process may be perfectly valid), but the crashing has been 100% reliable for all the systems I have developed for so far (Mac OS 68xxx, Mac OS PowerPC, Linux Redhat Pentium, Windows GUI Pentium, Windows console Pentium). For instance on PowerPC it is illegal (bus fault) to fetch a 4 byte integer from an odd address. What is a good value for this on 64-bit systems?

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  • Using static variable in function vs passing variable from caller

    - by Patrick
    I have a function which spawns various types of threads, one of the thread types needs to be spawned every x seconds. I currently have it like this: bool isTime( Time t ) { return t >= now(); } void spawner() { while( 1 ) { Time t = now(); if( isTime( t ) )//is time is called in more than one place in the real function { launchthread() t = now() + offset; } } } but I'm thinking of changing it to: bool isTime() { static Time t = now(); if( t >= now() ) { t = now() + offset; return true; } return false; } void spawner() { if( isTime() ) launchthread(); } I think the second way is neater but I generally avoid statics in much the same way I avoid global data; anyone have any thoughts on the different styles?

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  • Can I make ruby send network traffic over a specific iface?

    - by rjorgenson
    I am writing a script that grabs the external IP address along with some other information about each iface. I can't figure out how to make ruby send traffic over a specific iface(eth0 and wlan0 for example). I am currently using the open-uri library to open http://whatismyip.org and read it into a variable. def get_external_ip begin open("http://whatismyip.org") { |f| return f.read } rescue return "none" end end Is there any way to specify this at runtime of the script or from within the script itself(ideally)?

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  • Sparse quadratic program solver

    - by Jacob
    This great SO answer points to a good sparse solver, but I've got constraints on x (for Ax = b) such that each element in x is >=0 an <=N. The first thing which comes to mind is an QP solver for large sparse matrices. Also, A is huge (around 2e6x2e6) but very sparse with <=4 elements per row. Any ideas/recommendations?

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  • what is pagecache page

    - by kumar
    /* * Each physical page in the system has a struct page associated with * it to keep track of whatever it is we are using the page for at the * moment. Note that we have no way to track which tasks are using * a page, though if it is a pagecache page, rmap structures can tell us * who is mapping it. */ include/linux/mm_types.h Here Please lemme know what is "pagecache page" means? Thanks!

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  • Which languages are dynamically typed and compiled (and which are statically typed and interpreted)?

    - by Skilldrick
    In my reading on dynamic and static typing, I keep coming up against the assumption that statically typed languages are compiled, while dynamically typed languages are interpreted. I know that in general this is true, but I'm interested in the exceptions. I'd really like someone to not only give some examples of these exceptions, but try to explain why it was decided that these languages should work in this way.

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  • Are there any modern platforms with non-IEEE C/C++ float formats?

    - by Patrick Niedzielski
    Hi all, I am writing a video game, Humm and Strumm, which requires a network component in its game engine. I can deal with differences in endianness easily, but I have hit a wall in attempting to deal with possible float memory formats. I know that modern computers have all a standard integer format, but I have heard that they may not all use the IEEE standard for floating-point integers. Is this true? While certainly I could just output it as a character string into each packet, I would still have to convert to a "well-known format" of each client, regardless of the platform. The standard printf() and atod() would be inadequate. Please note, because this game is a Free/Open Source Software program that will run on GNU/Linux, *BSD, and Microsoft Windows, I cannot use any proprietary solutions, nor any single-platform solutions. Cheers, Patrick

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  • When is a scala partial function not a partial function?

    - by Fred Haslam
    While creating a map of String to partial functions I ran into unexpected behavior. When I create a partial function as a map element it works fine. When I allocate to a val it invokes instead. Trying to invoke the check generates an error. Is this expected? Am I doing something dumb? Comment out the check() to see the invocation. I am using scala 2.7.7 def PartialFunctionProblem() = { def dream()() = { println("~Dream~"); new Exception().printStackTrace() } val map = scala.collection.mutable.HashMap[String,()=>Unit]() map("dream") = dream() // partial function map("dream")() // invokes as expected val check = dream() // unexpected invocation check() // error: check of type Unit does not take parameters }

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  • Linker library for OpenMP for Snow Leopard?

    - by unknownthreat
    Currently, I am trying out OpenMP on XCode 3.2.2 on Snow Leopard: #include <omp.h> #include <iostream> #include <stdio.h> int main (int argc, char * const argv[]) { #pragma omp parallel printf("Hello from thread %d, nthreads %d\n", omp_get_thread_num(), omp_get_num_threads()); return 0; } I didn't include any linking libraries yet, so the linker complains: "_omp_get_thread_num", referenced from: _main in main.o "_omp_get_num_threads", referenced from: _main in main.o OK, fine, no problem, I take a look in the existing framework, looking for keywords such as openmp or omp... here comes the problem, where is the linking library? Or should I say, what is the name of the linking library for openMP? Is it dylib, framework or what? Or do I need to get it from somewhere first?

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  • Does MATLAB perform tail call optimization?

    - by Shea Levy
    I've recently learned Haskell, and am trying to carry the pure functional style over to my other code when possible. An important aspect of this is treating all variables as immutable, i.e. constants. In order to do so, many computations that would be implemented using loops in an imperative style have to be performed using recursion, which typically incurs a memory penalty due to the allocation a new stack frame for each function call. In the special case of a tail call (where the return value of a called function is immediately returned to the callee's caller), however, this penalty can be bypassed by a process called tail call optimization (in one method, this can be done by essentially replacing a call with a jmp after setting up the stack properly). Does MATLAB perform TCO by default, or is there a way to tell it to?

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  • Folder View in C# Form

    - by Kiran
    Hello, In an attempt to learn C#, I am trying to develop Picasa Like Application to display Photographs from my Library. Would it be possible to display folders as in Picasa Using C# ? Any help would be highly helpful.

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  • Effects of the `extern` keyword on C functions

    - by Elazar Leibovich
    In C I did not notice any effect of the extern keyword used before function declaration. At first I thougth that when defining extern int f(); in a single file forces you to implement it outside of the files scope, however I found out that both extern int f(); int f() {return 0;} And extern int f() {return 0;} Compiles just fine, with no warnings from gcc. I used gcc -Wall -ansi, he wouldn't even accept // comments. Are there any effects for using extern before function definitions? Or is it just an optional keyword with no side effects for functions. In the latter case I don't understand why did the standard designers chose to litter the grammar with superfluous keywords. EDIT: to clarify, I know there's usage for extern in variables, but I'm only asking about extern in functions.

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  • Abstracting boxed array structures in J

    - by estanford
    I've been working on a J function for a while, that's supposed to scan a list and put consecutive copies of an element into separate, concatenated boxes. My efforts have taken me as far as the function (<;. 2) ((2&(~:/\)),1:) which tests successive list entries for inequality, returns a list of boolean values, and cuts the list into boxes that end each time the number 1 appears. Here's an example application: (<;. 2) ((2&(~:/\)),1:) 1 2 3 3 3 4 1 1 1 +-+-+-----+-+-----+ |1|1|0 0 1|1|0 0 1| +-+-+-----+-+-----+ The task would be finished if I could then replace all those booleans with their corresponding values in the input argument. I've been looking for some kind of mystery function that would let me do something like final =: mysteryfunction @ (<;. 2) ((2&(~:/\)),1:) final 1 2 3 3 3 4 1 1 1 +-+-+-----+-+-----+ |1|2|3 3 3|4|1 1 1| +-+-+-----+-+-----+ In an ideal situation, there would be some way to abstractly represent the nesting pattern generated by (<;. 2) ((2&(~:/\)),1:) to the original input list. (i.e. "This boxed array over here has the first element boxed at depth one, the second element boxed at depth one, the third, fourth, and fifth elements boxed together at depth one,..., so take that unboxed list over there and box it up the same way.") I tried fooling around with ;. , S: , L:, L. and &. to produce that behavior, but I haven't had much luck. Is there some kind of operator or principle I'm missing that could make this happen? It wouldn't surprise me if I were overthinking the whole issue, but I'm running out of ideas.

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  • F#: how to find Cartesian power

    - by Nike
    I have a problem with writing a Cartesian power function. I found many examples about calculating Cartesian Product, but no one about Cartesian power. For example, [1;2] raised to power 3 = [ [1;1;1] ; [1;1;2] ; [1;2;1] ; [1;2;2] ; [2;1;1] ; [2;1;2] ; [2;2;1]; [2;2;2] ] I use following code to calculate Cartesian Product: let Cprod U V = let mutable res = [] for u in U do for v in V do res <- res @ [[u;v]] res And trying to calculate Cartesian power. I use following code to calculate Cartesian Product: let Cpower U n = let mutable V = U for i=0 to n-1 do V <- Dprod U V V Visual Studio said: Error The resulting type would be infinite when unifying ''a' and ''a list'. I will thankful for any help and links.

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  • How do I setup a Python development environment on Linux ?

    - by Rob Sobers
    I'm a .NET developer who knows very little about Python, but want to give it a test drive for a small project I'm working on. What tools and packages should I install on my machine? I'm looking for a common, somewhat comprehensive, development environment. I'll likely run Ubuntu 9.10, but I'm flexible. If Windows is a better option, that's fine too.

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  • A question for retrieve minix os version

    - by majnun
    Hi guys i'm having a project for the university in which (above others ) i have to get the minix os version from kernell call.I'm not a very experienced programmer so this is what i have come to (with some help ) int main (int argc, char *argv[] ) { char M3ca1[23]; message ml; m.m_u.m_m1.m3ca1= OS_VERSION; char temp=_syscall(MM,69,&m); printf("the os version is %c\n",temp); return 0; } and i get multiple errors.IF you have any ideas it would be greatly appreciated.

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