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  • Sparse linear 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 LP solver for large sparse matrices. Any ideas/recommendations?

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  • Are there any code critique sites or similar resources?

    - by Ukko
    I have noticed when people post example code illustrating some issue that they are having often they will gather a number of comments addressing the quality of the code they presented and not the actual problem asked. This is very helpful--if not well directed. Often, this is wasted effort since the asker is often not receptive and the code is often chopped down to something small to post leaving lots of rough edges. In the old days you would see people asking questions like this on comp.lang.lisp and other parts of the comp.lang hierarchy. But that bit of the net kind of sank into the sewers of neglect. Is there a comparable one-stop-shop today? I am partially asking for selfish reasons, I know how to write good idiomatic C, Lisp, O'Caml, and Java code. But I learned C++ pre-template and STL, those rusty skills are not really applicable to today's C++. I have picked up languages like Scala in a vacuum and get by, but am I really doing it correctly? There are so many ways you can abuse a language, I am currently working against a codebase of Fortran written in C, and I recognize and loathe the "that guy" who wrote it. I don't want to be someone else's "that guy" if I can help it. Just because it works does not mean that one did not totally miss the boat on how it should have been done. Do you seek out this type of critique? If so how, where and why? What types of benefits do you derive from it? How about abuse and trolls?

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  • How can I pass methods in javascript?

    - by peterjwest
    I often need to pass methods from objects into other objects. However I usually want the method to be attached to the original object (by attached I mean 'this' should refer to the original object). I know a few ways to do this: a) In the object constructor: ObjectA = function() { var that = this; var method = function(a,b,c) { that.abc = a+b+c }} b) In objectA which has been passed objectB: objectB.assign(function(a,b,c) { that.method(a,b,c) }) c) Outside both objects: objectB.assign(function(a,b,c) { objectA.method(a,b,c) }) I want to know if there is a simpler way to pass methods attached to their original objects.

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  • Supporting Piping (A Useful Hello World)

    - by blastthisinferno
    I am trying to write a collection of simple C++ programs that follow the basic Unix philosophy by: Make each program do one thing well. Expect the output of every program to become the input to another, as yet unknown, program. I'm having an issue trying to get the output of one to be the input of the other, and getting the output of one be the input of a separate instance of itself. Very briefly, I have a program add which takes arguments and spits out the summation. I want to be able to pipe the output to another add instance. ./add 1 2 | ./add 3 4 That should yield 6 but currently yields 10. I've encountered two problems: The cin waits for user input from the console. I don't want this, and haven't been able to find a simple example showing a the use of standard input stream without querying the user in the console. If someone knows of an example please let me know. I can't figure out how to use standard input while supporting piping. Currently, it appears it does not work. If I issue the command ./add 1 2 | ./add 3 4 it results in 7. The relevant code is below: add.cpp snippet // ... COMMAND LINE PROCESSING ... std::vector<double> numbers = multi.getValue(); // using TCLAP for command line parsing if (numbers.size() > 0) { double sum = numbers[0]; double arg; for (int i=1; i < numbers.size(); i++) { arg = numbers[i]; sum += arg; } std::cout << sum << std::endl; } else { double input; // right now this is test code while I try and get standard input streaming working as expected while (std::cin) { std::cin >> input; std::cout << input << std::endl; } } // ... MORE IRRELEVANT CODE ... So, I guess my question(s) is does anyone see what is incorrect with this code in order to support piping standard input? Are there some well known (or hidden) resources that explain clearly how to implement an example application supporting the basic Unix philosophy? @Chris Lutz I've changed the code to what's below. The problem where cin still waits for user input on the console, and doesn't just take from the standard input passed from the pipe. Am I missing something trivial for handling this? I haven't tried Greg Hewgill's answer yet, but don't see how that would help since the issue is still with cin. // ... COMMAND LINE PROCESSING ... std::vector<double> numbers = multi.getValue(); // using TCLAP for command line parsing double sum = numbers[0]; double arg; for (int i=1; i < numbers.size(); i++) { arg = numbers[i]; sum += arg; } // right now this is test code while I try and get standard input streaming working as expected while (std::cin) { std::cin >> arg; std::cout << arg << std::endl; } std::cout << sum << std::endl; // ... MORE IRRELEVANT CODE ...

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  • What language is this???

    - by Misha Koshelev
    Dear All: I thought this was Javascript... but parser is giving me trouble. Any ideas? Thank you! Misha for (;;); {"error":0,"errorSummary":"","errorDescription":"","errorIsWarning":false,"silentError":0,"payload":{"collections": [{"name":"bcm","type":"flp","filter":"flp_662923563701","value":"662923563701","editable":true,"deletable":true,"members": ["1319651388","539562714","710814793","569071038","1553739575","2413243"]}, {"name":"mstp","type":"flp","filter":"flp_715806870131","value":"715806870131","editable":true,"deletable":true,"members": ["1263807225","1159429816","508447486","508005223","1234906348","642723993","552875889","23401888","10701320","8302901","7931988","3007490","1286522890","1128447272","1076062553","775679867","737520202","640799498","224400055","224400048","14211567","7909445","3005965","2404364","218216","660037273","224400089","73306230","9603033","1111694","1034418884","775680513" ,"704526828","518753881","512477182","224400016","24904610","19000876","5403952","3005641","2100348","100000421128298","1445411167","691445174","1020020100","795471177","683724539","682441089","532450522","224400129","224400005","3006522","2246813","1302265","7197","1900494", "100000474978266","2533582","1205125","1384091677","1260996959","710814793","514951289","224400164","224400156","173601800","13304723","7938844","3004783","3001379","302817","716739950 ","706849","1418109424","562676898","82501644","3007569","13173"]}, {"name":"mystery","type":"flp","filter":"flp_687949656211","value":"687949656211","editable":true,"deletable":true,"members": ["100001286464748","508123007","100001161894460","1148567030","1048974191","769992391","831734347","15347","1297180076","756692945","3005266","733396195","34410910","100000940154241"," 748426280","569417581","1318922027","100000164920046","1475269609","1436536592","10000016210 8385","754095305","100000421128298","537833189","100000692471928","7920231","673753496","3006217","1221878","8365333","1128447272","224400133","218216","505457123","1421958541","183829 5926","2349408","1622810085","1201640391","510959992","23429895","542118016","1017385668","586225579","625100539","100000474886633","26404148","1384091677","224400156","806908635","843 187401","400435","768261176","7901808","748496482","1541469473","2511982","25401573","503715 506","1226000844","559195162","41400094","1099436201","409816","1584400985","1577092523","100000349351880","199301581"]},{"name":"SMS Subscriptions","type":"ms","filter":"ms","value":"3","editable":true,"deletable":false,"members":[]}],"current_view":false}}

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  • Where to draw the line between efficiency and practicality

    - by dclowd9901
    I understand very well the need for websites' front ends to be coded and compressed as much as possible, however, I feel like I have more lax standards than others when it comes to practical applications. For instance, while I understand why some would, I don't see anything wrong with putting selectors in the <html> or <body> tags on a website with an expected small visitation rate. I would only do this for a cheap website for a small client, because I can't really justify the cost of time otherwise. So, that said, do you think it's okay to draw a line? Where do you draw yours?

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  • How to modify Keyboard interrupt (under Windows XP) from a C++ Program ?

    - by rockr90
    Hi everyone ! We have been given a little project (As part of my OS course) to make a Windows program that modifies keyboard input, so that it transforms any lowercase character entered into an uppercase one (without using caps-lock) ! so when you type on the keyboard you'll see what you're typing transformed into uppercase ! I have done this quite easily using Turbo C by calling geninterrupt() and using variables _AH, _AL, i had to read a character using: _AH = 0x07; // Reading a character without echo geninterrupt(0x21); // Dos interrupt Then to transform it into an Upercase letter i have to mask the 5th bit by using: _AL = _AL & 0xDF; // Masking the entered character with 11011111 and then i will display the character using any output routine. Now, this solution will only work under old C DOS compilers. But what we intend to do is to make a close or similar solution to this by using any modern C/C++ compiler under Windows XP ! What i have first thought of is modifying the Keyboard ISR so that it masks the fifth bit of any entered character to turn it uppercase ! But i do not know how exactly to do this. Second, I wanted to create a Win32 console program to either do the same solution (but to no avail) or make a windows-compatible solution, still i do not know which functions to use ! Third I thought to make a windows program that modifies the ISR directly to suit my needs ! and i'm still looking for how to do this ! So please, If you could help me out on this, I would greatly appreciate it ! Thank you in advance ! (I'm using Windows XP on intel X86 with mingw-GCC compiler.)

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  • UNIX script to parse Zone file (is this the best code?)

    - by Steve
    Hi, FOund the following on: http://mike.murraynet.net/2009/08/23/parsing-the-verisign-zone-file-with-os-x/ Can unix-masters have a look at it and see if its the best possible way to gather the unique domainsnames in a zone file? For .NET domains: grep “^[a-zA-Z0-9-]+ NS .” net.zone|sed “s/NS .//”|uniq netdomains.txt For .COM domains: grep “^[a-zA-Z0-9-]+ NS .” com.zone|sed “s/NS .//”|uniq comdomains.txt For .EDU domains: grep “^[a-zA-Z0-9-]+ NS .” edu.zone|sed “s/NS .//”|uniq edudomains.txt

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  • C++ String manipulation isn't making sense to me...

    - by Andrew Bolster
    I am trying some of the Stanford SEE courses online to learn some new languages; this particular assignment has to do with removing substrings from strings. What I've got so far is below, but if text = "hello hello" and remove ="el", it gets stuck in a loop, but if i change text to text = "hello hllo", it works, making me think I'm doing something obviously stupid. There is a stipulation in the assignment not to modify the incoming strings, and instead to return a new string. string CensorString1(string text, string remove){ string returned; size_t found=0, lastfound=0; found = (text.substr(lastfound,text.size())).find(remove); while (string::npos != found ){ returned += text.substr(lastfound,found); lastfound = found + remove.size(); found = (text.substr(lastfound,text.size())).find(remove); } returned += text.substr(lastfound,found); return returned; } Guidance would be appreciated :-) Thanks

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  • What is the Software Development Lifecycle?

    - by j-t-s
    Our investor wants a SDLC. I've never written one before, and I don't have enough time to go and buy a book, or spend much time learning about them. From what I've been told about them, they consist of requirements (what needs to be done), and a list is done. Is this correct? Update: I have found this article which really helps to explain things in simple terms and very quickly. Not that I think an SDLC should be done quickly. In my case, I have no other option.

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  • What is your company's stance on Developers using Laptops?

    - by codepunk
    I am a developer and my company is moving towards a "no laptop" policy in fear of them being lost or stolen and source code being compromised. Now I don't work for NASA, the military or anything labeled Top Secret but our code is very important to our business nonetheless (as all source code would be). I'll be honest, I disagree with this policy against laptops and wanted to see what others think. I'd like to know: What is your team/company's stance on laptops Your company's size and/or field (small, medium or large, Fortune 500, etc). Whether you've had to take any extra precautions (signing any additional legal, ensure your hard drive is encrypted, etc). Thanks!

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  • MySQL: Get only count of result set.

    - by Varun
    I am using MVC with PHP/MySQL. Suppose I am using 10 functions with different queries for fetching details from the database. But at other times I may want to get only the count of the result that will be returned by the query. What is the standard way to handle such situation. Should I write 10 more functions which duplicate almost whole query and return only the count. Or Should I always return the count also with the result set Or I can pass a flag to indicate that the function should return count only, and then based on the flag I will dynamically generate the (select part of) query. Or Is there a better way?

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  • socket timeout and remove O_NONBLOCK option

    - by juxstapose
    Hello, I implemented a socket timeout and retry but in order to do it I had to set the socket as a non-blocking socket. However, I need the socket to block. This was my attempt at a solution to these two problems. This is not working. Subsequent send calls block but never send any data. When I connect without the select and the timeout, subsequent send calls work normally. References: C: socket connection timeout How to reset a socket back to blocking mode (after I set it to nonblocking mode)? Code: fd_set fdset; struct timeval tv; fcntl(dsock, F_SETFL, O_NONBLOCK); tv.tv_sec = theDeviceTimeout; tv.tv_usec = 0; int retries=0; logi(theLogOutput, LOG_INFO, "connecting to device socket num retrys: %i", theDeviceRetry); for(retries=0;retries<theDeviceRetry;retries++) { connect(dsock, (struct sockaddr *)&daddr, sizeof daddr); FD_ZERO(&fdset); FD_SET(dsock, &fdset); if (select(dsock + 1, NULL, &fdset, NULL, &tv) == 1) { int so_error; socklen_t slen = sizeof so_error; getsockopt(dsock, SOL_SOCKET, SO_ERROR, &so_error, &slen); if (so_error == 0) { logi(theLogOutput, LOG_INFO, "connected to socket on port %i on %s", theDevicePort, theDeviceIP); break; } else { logi(theLogOutput, LOG_WARN, "connect to %i failed on ip %s because %s retries %i", theDevicePort, theDeviceIP, strerror(errno), retries); logi(theLogOutput, LOG_WARN, "failed to connect to device %s", strerror(errno)); logi(theLogOutput, LOG_WARN, "error: %i %s", so_error, strerror(so_error)); continue; } } } int opts; opts = fcntl(dsock,F_GETFL); logi(theLogOutput, LOG_DEBUG, "clearing nonblock option %i retries %i", opts, retries); opts ^= O_NONBLOCK; fcntl(dsock, F_SETFL, opts);

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  • What do you call this functional language feature?

    - by Jimmy
    ok, embarrassing enough, I posted code that I need explained. Specifically, it first chains absolute value and subtraction together, then tacks on a sort, all the while not having to mention parameters and arguments at all, because of the presense of "adverbs" that can join these functions "verbs" What (non-APL-type) languages support this kind of no-arguments function composition (I have the vague idea it ties in strongly to the concepts of monad/dyad and rank, but its hard to get a particularly easy-to-understand picture just from reading Wikipedia) and what do I call this concept?

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  • Problem with .release behavior in file_operations

    - by Yannick
    Hello, I'm dealing with a problem in a kernel module that get data from userspace using a /proc entry. I set open/write/release entries for my own defined /proc entry, and manage well to use it to get data from userspace. I handle errors in open/write functions well, and they are visible to user as open/fopen or write/fwrite/fprintf errors. But some of the errors can only be checked at close (because it's the time all the data is available). In these cases I return something different than 0, which I supposed to be in some way the value 'close' or 'fclose' will return to user. But whatever the value I return my close behave like if all is fine. To be sure I replaced all the release() code by a simple 'return(-1);' and wrote a program that open/write/close the /proc entry, and prints the close return value (and the errno). It always return '0' whatever the value I give. Behavior is the same with 'fclose', or by using shell mechanism (echo "..." /proc/my/entry). Any clue about this strange behavior that is not the one claimed in many tutorials I found? BTW I'm using RHEL5 kernel (2.6.18, redhat modified), on a 64bit system. Thanks. Regards, Yannick

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  • What coding standards do you follow?

    - by Mark Szymanski
    I was just curious what coding standards people followed. I for one use the following: Brackets ALWAYS go on the next line. For instance: int main() { //Blah... } I never use code folding. (Yes my IDE's do support it (Xcode and Eclipse). Put related functions/methods single-spaced, otherwise double space. Here is an example: int foo = 0; printf("%d",foo); those are related while these are not: printf("Hello, World!"); return(0); I don't put else statements on the same line as the closing bracket for the preceding if statement. Most of the time in Java if a program needs multiple try catch statements I will just put the whole thing in one try catch.

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  • Property value of a String object in JavaScript

    - by naivists
    As far as I understand, every string is an object in Javascript. Still, it "does not work" as I expect it to be: var a="abc"; //here we get a new string object a.b = 123; //I seem to declare a property "b" of that object alert(a.b); //alerts "undefined" However, if I try to define a string in the "wrong way", everything works as expected var a=new String("abc"); // a.b = 123; alert(a.b); //alerts "123" Why is that so?

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  • Why isn't LISP more widely used?

    - by Chris
    I've heard a lot of people espouse the capabilities of LISP and its omnipotent macros. If LISP is such a great language, why isn't it being adopted more? What problems is LISP facing that is holding it back from (re)emerging as popular language? Is it something about LISP itself ("those brackets!" isn't the answer, is it?!), or its competitors (e.g. the dominance of Java, .NET)?

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