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  • How to loop through a boost::mpl::list?

    - by Kyle
    This is as far as I've gotten, #include <boost/mpl/list.hpp> #include <algorithm> namespace mpl = boost::mpl; class RunAround {}; class HopUpAndDown {}; class Sleep {}; template<typename Instructions> int doThis(); template<> int doThis<RunAround>() { /* run run run.. */ return 3; } template<> int doThis<HopUpAndDown>() { /* hop hop hop.. */ return 2; } template<> int doThis<Sleep>() { /* zzz.. */ return -2; } int main() { typedef mpl::list<RunAround, HopUpAndDown, Sleep> acts; // std::for_each(mpl::begin<acts>::type, mpl::end<acts>::type, doThis<????>); return 0; }; How do I complete this? (I don't know if I should be using std::for_each, just a guess based on another answer here)

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  • Function syntax puzzler in scalaz

    - by oxbow_lakes
    Following watching Nick Partidge's presentation on deriving scalaz, I got to looking at this example, which is just awesome: import scalaz._ import Scalaz._ def even(x: Int) : Validation[NonEmptyList[String], Int] = if (x % 2 ==0) x.success else "not even: %d".format(x).wrapNel.fail println( even(3) <|*|> even(5) ) //prints: Failure(NonEmptyList(not even: 3, not even: 5)) I was trying to understand what the <|*|> method was doing, here is the source code: def <|*|>[B](b: M[B])(implicit t: Functor[M], a: Apply[M]): M[(A, B)] = <**>(b, (_: A, _: B)) OK, that is fairly confusing (!) - but it references the <**> method, which is declared thus: def <**>[B, C](b: M[B], z: (A, B) => C)(implicit t: Functor[M], a: Apply[M]): M[C] = a(t.fmap(value, z.curried), b) So I have a few questions: How come the method appears to take a monad of one type parameter (M[B]) but can get passed a Validation (which has two type paremeters)? How does the syntax (_: A, _: B) define the function (A, B) => C which the 2nd method expects? It doesn't even define an output via =>

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  • install linux guest on windows host using a .iso file on vmserver 2.0

    - by Bob
    I have done this in vmserver 1.0. I set the Cd to point to the .iso file. Then I start the vm and it starts to install. I am on the summary screen. I have created a VM. I go to CD/DVD - edit I change the radio button to Host Medio Then I select ISO Image and Browse. Here is the problem: Then in my browser I get Inventory - Virtual Machine (directory) I don't know where that directory is. I have my ISO's in a folder on my desktop. I can't browse to my desktop. When I try to just put in a path such as c:\mydesktop\mylinuxdirectory\linux1.iso The following problems have been found:OKThe ISO Image File Path must be a valid file path in the format: "[datastore] /path/to/isoimage.iso". so how do I browse to an ISO? I can add the iso after I start the VM, but by then its too late and the VM says no Operating System installed.

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  • How to redraw the picture while moving windows in openGL?

    - by tsubasa
    I have drawn a picture with openGL on my windows. Now whenever I hold the mouse button on the windows and move it, my picture always got distorted. I don't know what function in openGL that can help me redraw the picture while the windows is moved. Anybody could help? I tried this but seems not work: void myDisplay() { ..... } void reshape(int x, int y) { glutPostRedisplay(); } int main() { ..... glutDisplayFunc(myDisplay); glutReshapeFunc(reshape); }

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  • ByteStrings in Haskell

    - by Jon
    So i am trying to write a program that can read in a java class file as bytecode. For this i am using Data.Binary and Data.ByteStream. The problem i am having is because im pretty new to Haskell i am having trouble actually using these tools. module Main where import Data.Binary.Get import Data.Word import qualified Data.ByteString.Lazy as S getBinary :: Get Word8 getBinary = do a <- getWord8 return (a) main :: IO () main = do contents <- S.getContents print (getBinary contents) This is what i have come up with so far and i fear that its not really even on the right track. Although i know this question is very general i would appreciate some help with what i should be doing with the reading.

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  • Clear data at serial port in Linux in C?

    - by ipkiss
    Hello guys, I am testing the sending and receiving programs with the code as The main() function is below: include include include include include include include "read_write.h" int fd; int initport(int fd) { struct termios options; // Get the current options for the port... tcgetattr(fd, &options); // Set the baud rates to 19200... cfsetispeed(&options, B9600); cfsetospeed(&options, B9600); // Enable the receiver and set local mode... options.c_cflag |= (CLOCAL | CREAD); options.c_cflag &= ~PARENB; options.c_cflag &= ~CSTOPB; options.c_cflag &= ~CSIZE; options.c_cflag |= CS8; // Set the new options for the port... tcsetattr(fd, TCSANOW, &options); return 1; } int main(int argc, char **argv) { fd = open("/dev/pts/2", O_RDWR | O_NOCTTY | O_NDELAY); if (fd == -1) { perror("open_port: Unable to open /dev/pts/1 - "); return 1; } else { fcntl(fd, F_SETFL, 0); } printf("baud=%d\n", getbaud(fd)); initport(fd); printf("baud=%d\n", getbaud(fd)); char sCmd[254]; sCmd[0] = 0x41; sCmd[1] = 0x42; sCmd[2] = 0x43; sCmd[3] = 0x00; if (!writeport(fd, sCmd)) { printf("write failed\n"); close(fd); return 1; } printf("written:%s\n", sCmd); usleep(500000); char sResult[254]; fcntl(fd, F_SETFL, FNDELAY); if (!readport(fd,sResult)) { printf("read failed\n"); close(fd); return 1; } printf("readport=%s\n", sResult); close(fd); return 0; } read_write.h: #include <stdio.h> /* Standard input/output definitions */ include /* String function definitions */ include /* UNIX standard function definitions */ include /* File control definitions */ include /* Error number definitions */ include /* POSIX terminal control definitions */ int writeport(int fd, char *chars) { int len = strlen(chars); chars[len] = 0x0d; // stick a after the command chars[len+1] = 0x00; // terminate the string properly int n = write(fd, chars, strlen(chars)); if (n < 0) { fputs("write failed!\n", stderr); return 0; } return 1; } int readport(int fd, char *result) { int iIn = read(fd, result, 254); result[iIn-1] = 0x00; if (iIn < 0) { if (errno == EAGAIN) { printf("SERIAL EAGAIN ERROR\n"); return 0; } else { printf("SERIAL read error %d %s\n", errno, strerror(errno)); return 0; } } return 1; } and got the issue: In order to test with serial port, I used the socat (https://help.ubuntu.com/community/VirtualSerialPort ) to create a pair serial ports on Linux and test my program with these port. The first time the program sends the data and the program receives data is ok. However, if I read again or even re-write the new data into the serial port, the return data is always null until I stop the virtual serial port and start it again, then the write and read data is ok, but still, only one time. (In the real case, the sending part will be done by another device, I am just taking care of the reading data from the serial port. I wrote both parts just to test my reading code.) Does anyone have any ideas? Thanks a lot.

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  • Can immutable be a memory hog?

    - by ciscoheat
    Let's say we have a memory-intensive class like an Image, with chainable methods like Resize() and ConvertTo(). If this class is immutable, won't it take a huge amount of memory when I start doing things like i.Resize(500, 800).Rotate(90).ConvertTo(Gif), compared to a mutable one which modifies itself? How to handle a situation like this in a functional language?

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  • Sparse constrained linear least-squares 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? I'm looking for something like MATLAB's lsqlin but with huge sparse matrices.

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  • Scala/Erlang use something like greenThread or not ?

    - by CHAPa
    Hi all, Im reading a lot about how scala/Erlang does lightweight threads and your concurrency model ( Actor Model ). Off course, some doubts appear in my head. Scala/Erlang use a approach similar to the old thread model used by java (greenThread) ? for example, suppose that there is a machine with 2 cores, so the scala/erlang environment will fork one thread per processor ? The other threads will be scheduled by user-space( scala VM / erlang vm ) environment. is it correct ? how under the hood that really work ? thanks a lot.

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  • I need to write a program that reads angles in radians from an input disk and converts them in degre

    - by Amadou
    Write a program that reads angles in radians from an input disk le and converts them into degrees, minutes, and seconds. Output should be written into another le. A sample input le could be: # this is a comment # your program should be able to skip comment lines # and blank lines # input radian numbers could be seperated by blanks 0.0 1.0 # or by a newline 3.141593 6.0

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  • Any Win32 APIs to get the screenshots?

    - by Microkernel
    Hi all, I am writing an app, which needs to take the screen shots automatically (just like pressing PrintScreen button). So please suggest me how to get this done. A raw 24 bit BMP image would suffice. PLEASE NOTE: My app is in C, so any win32 APIs that can be called from my code is what I am looking for. (Sometimes back I had got an example code from codeproject which used to get the screen shots but the mouse pointer user to blink when the screen shot is taken. As multiple shots are taken this looks irritating to the user, so I don't want the mouse pointer to blink!) Regards, Chethan KR

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  • Do you have any tips for comments code to keep them in step with the code?

    - by Rob Wells
    G'day, I've read both of Steve McConnell's excellent Code Complete books "Code Complete" and "Code Complete 2" and was wondering if people have any other suggestions for commenting code. My commenting mantra could be summed up by the basic idea of expressing "what the code below cannot say". While enjoying this interesting blog post by Jeff about commenting I was still left wondering "When coding, when do you feel a comment is required?" Edit: Oops. Seems to be a duplicate of this question http://stackoverflow.com/questions/121945/how-do-you-like-your-comments so sorry for the noise. Thanks to my, seemingly, SO shadow for pointing it out - wouldn't have thought I was that interesting. Now off to read the original post and see if it is relevant. Edit: I meant to emphasise the best appraoch to ensure that your comments will stay in step with the code. Maybe expressing an intent rather than the mechansim for instance.

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  • 'foreach' failing when using Parallel Task Library

    - by Chris Arnold
    The following code creates the correct number of files, but every file contains the contents of the first list. Can anyone spot what I've done wrong please? private IList<List<string>> GetLists() { // Code omitted for brevity... } private void DoSomethingInParallel() { var lists = GetLists(); var tasks = new List<Task>(); var factory = new TaskFactory(); foreach (var list in lists) { tasks.Add(factory.StartNew(() => { WriteListToLogFile(list); })); } Task.WaitAll(tasks.ToArray()); }

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  • How do you handle your "Project Manager"

    - by Vecdid
    I currently work for a company who recently has downsized. I do all in house work, client installs, builds,q.a, well basically all the in house work. My direct boss is VERY untechnical and lately I have found it VERY hard to deal with his lack of knowledge. The biggest issues I have had are as follows: I am on many deadlines at a time. I get stopped to put together a half fast quote as I cannot be late on the deadline, in the meantime, three support calls comes in, I give quote, time too much so they outsource it. I then I have to fix everything the vendor broke. I get asked, when an issue arrises, why is the issue occurring and explain in detail, yet that detail means absolutly nothing to him. All he cares about are deadlines, yet he is the one who schdules everything. "I am a programmer not a graphic designer, meaqns nothing to him" I was hired as a .NET programmer, yet they let a vendor choose wordpress for many sites(yeah I had to learn all about it quick) I guess I can go on and on, but has anyone had to deal with this type of project manager? What is some advice, other than finding another job. Thanks in advance, and I made this a wiki, so please don't close...

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  • The Benefits of Constants

    - by onaclov2000
    I understand one of the big deals about constants is that you don't have to go through and update code where that constant is used all over the place. Thats great, but let's say you don't explicitly declare it as a constant. What benefit(s) exist(s) to take a variable that HAPPENS to actually not be changed and make it a constant, will this save on processing, and/or size of code...etc? Basically I have a program that the compiler is saying that a particular variable is not changed and thus can be declared a constant, I just wanted to know what the benefit to adding the constant qualifier to it would be, if it makes no difference then making that change adds no value and thus no point wasting time (this same scenario occurs in more then one place) going back and "fixing" all these variables. Thank you, onaclov

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  • Functional data structures in C++

    - by drg
    Does anyone know of a C++ data structure library providing functional (a.k.a. immutable, or "persistent" in the FP sense) equivalents of the familiar STL structures? By "functional" I mean that the objects themselves are immutable, while modifications to those objects return new objects sharing the same internals as the parent object where appropriate. Ideally, such a library would resemble STL, and would work well with Boost.Phoenix (caveat- I haven't actually used Phoenix, but as far as I can tell it provides many algorithms but no data structures, unless a lazily-computed change to an existing data structure counts - does it?)

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  • How hard is FizzBuzz? [closed]

    - by Josh K
    After reading various blog entries I took it upon myself to code a FizzBuzz program in PHP. class FizzBuzz { function __construct() { } function go() { for($i = 1; $i < 101; $i++) { if($i % 3 == 0 and $i % 5 == 0) { echo("FizzBuzz\n"); continue; } else if($i % 3 == 0) { echo("Fizz\n"); continue; } else if($i % 5 == 0) { echo("Buzz\n"); continue; } else { echo($i."\n"); } } } } $FB = new FizzBuzz(); $FB->go(); Created the FizzBuzz object just because I could, I complete this in under five minutes. Is it really that hard to do?

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