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• How do I generate different yyparse functions from lex/yacc for use in the same program?

  - by th

  Hi, I want to generate two separate parsing functions from lex/yacc. Normally yacc gives you a function yyparse() that you can call when you need to do some parsing, but I need to have several different yyparses each associated with different lexers and grammars. The man page seems to suggest the -p (prefix) flag, but this didn't work for me. I got errors from gcc that indicated that yylval was not properly being relabeled (i.e. it claims that several different tokens are not defined). Does anyone know the general rpocedure for generating these separate functions? thanks

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• Choosing a plotting library for web/browser application

  - by Goro

  Hello, I am looking for a plotting/graphing library (mostly to do line plots) for my application. I have been looking at JavaScript APIs (like Google's) but I found them to be slowing down things at client side (I am plotting a quite large number of points). I also found that with client-side libraries, the performance was quite varied depending on the user's computer. With moving to a server-side library I would cut down on this variance, and would have more control over data flow (my data is in a MySQL database). I have then looked at some PHP-based plotting libraries, but a lot of them seem to be "forgotten" (no new version for years). I have been eying pChart, but it has not had an update in almost two years. First, what would you recommend: server-side or client-side approach? Second, what library would you recommend. Paid libraries are definitely an option, as I don't mind paying for quality software that would cut down on my development time. Thanks,

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• jQuery Resizable() UI Problem

  - by OneNerd

  In general, resizable() works fine. Here is where I am getting into an issue. I have a div that contains some resizable items that work fine (resizable() applied to them at some point). user can save items for later view (the innerHTML of the div gets saved into a JavaScript array, then div gets cleared so they can do something else) When items get placed back onto div (from array) -- I do a $('#divname').append(arrayname[i]); -- items are no longer resizable (although visually they have the resizable classes/handle on them) Here is what I have tried so far (none of which have worked): After append() line, I re-initialize the resizable -- $('#items').resizable(); After append() line, remove then re-add resizable -- $('#items').resizable('destroy').resizable(); Any help is appreciated - thanks.

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• How do you sort files numerically?

  - by Zachary Young

  Hello all, First off, I'm posting this because when I was looking for a solution to the problem below, I could not find one on stackoverflow. So, I'm hoping to add a little bit to the knowledge base here. I need to process some files in a directory and need the files to be sorted numerically. I found some examples on sorting--specifically with using the lamba pattern--at wiki.python.org, and I put this together: #!env/python import re tiffFiles = """ayurveda_1.tif ayurveda_11.tif ayurveda_13.tif ayurveda_2.tif ayurveda_20.tif ayurveda_22.tif""".split('\n') numPattern = re.compile('_(\d{1,2})\.', re.IGNORECASE) tiffFiles.sort(cmp, key=lambda tFile: int(numPattern.search(tFile).group(1))) print tiffFiles I'm still rather new to Python and would like to ask the community if there are any improvements that can be made to this: shortening the code up (removing lambda), performance, style/readability? Thank you, Zachary

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• How can I prevent users from taking screenshots of my application window?

  - by Midday

  What are some methods to prevent screenshots from being taken, if any? I've considered setting the "Print Screen" button as a hotkey, which makes the window fuzzy. However, there would be the problem of other 3rd party screenshot tools. How can I prevent their use? Why would I want such a thing? The idea is to create a chat client which you can't share the chatted information with others, not by copy & paste nor by print screen... Looking for general ideas or suggestions rather than actual code.

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• nginx-tornado-django request timeout

  - by Xie

  We are using nginx-tornado-django to provide web services. That is, no web page frontend. The nginx server serves as a load-balancer. The server has 8 cores, so we launched 8 tornado-django processes on every server. Memcached is also deployed to gain better performance. The requests per day is about 1 million per server. We use MySQL as backend DB. The code is tested and correct. Our profiling shows that normally every request are processed within 100ms. The problem is, we find that about 10 percent of the requests suffers from time-out issue. Many requests didn't even reach tornado. I really don't have much experience on tuning of nginx/tornado/MySQL. Right now I don't have a clue on what is going wrong. Any advise is appreiciated.

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• How to think in data stores instead of databases?

  - by Jim

  As an example, Google App Engine uses data stores, not a database, to store data. Does anybody have any tips for using data stores instead of databases? It seems I've trained my mind to think 100% in object relationships that map directly to table structures, and now it's hard to see anything differently. I can understand some of the benefits of data stores (e.g. performance and the ability to distribute data), but some good database functionality is sacrificed (e.g. joins). Does anybody who has worked with data stores like BigTable have any good advice to working with them?

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• Has anyone ever encountered a Monad Transformer in the wild?

  - by martingw

  In my area of business - back office IT for a financial institution - it is very common for a software component to carry a global configuration around, to log it's progress, to have some kind of error handling / computation short circuit... Things that can be modelled nicely by Reader-, Writer-, Maybe-monads and the like in Haskell and composed together with monad transformers. But there seem to some drawbacks: The concept behind monad transformers is quite tricky and hard to understand, monad transformers lead to very complex type signatures, and they inflict some performance penalty. So I'm wondering: Are monad transformers best practice when dealing with those common tasks mentioned above?

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• What messaging technologies in windows-ce for gauranteed msg delivery?

  - by Aidanapword

  All, We are building a windows-ce (6.0R3) based device that requires guaranteed and audit-ready message delivery (including store & forward) up to and down from the cloud. I have been looking for choices beyond: MSMQ a proprietary solution (what our prototype device is using) AMQP (research on using this in our context is now starting) ... are there any others? We will be transporting sensitive data (who isn't?!?!) over a public network, and large scale options are required. Anything running on an embedded device will be performance sensitive too. Thanks! Aidanapword

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• code for find out nth larget number in an array by using perl

  - by user136104

  I have written following code in perl #!/usr/bin/perl @array =(3,6,8,1,2); my $second_largest =0; my $largest = 0; for (@array) { if($_ > $largest) { $second_largest = $largest; $largest = $_; } if($_ > $second_largest && $_ < $largest) { $second_largest = $_; } } print "Second largest::".$second_largest; print "largest::".$largest; But I need a general code to find out "Nth" largest and smallest number of an array Plz help me

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• Can games be considered real-time systems?

  - by harry

  I've been reading up on real-time systems and how they work etc. I was looking at the wikipedia article as well that said a game of Chess with a timer per move can be considered a real-time system because the program MUST compute a move in that time. What about other games? As we know, games generally try and run at 25+ FPS, could it be considered a soft real-time system since if it falls under 25 (I'm using 25 as a pre-defined threshold btw) it's not the end of the world, just a hit to the performance that we wanted? Also - games have events they must handle as well. The user uses the keyboard/mouse and the system must answer those events accordingly within (again) a pre-defined time, before the game is considered to have "failed". Oh, and I'm talking single-player for now to keep things simple. It sounds like games fit the soft real-time system criteria, but I'd like to know if I'm missing anything... thanks.

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• Ampersand in link description text?

  - by kitenski

  I am validating my site using validator.w3.org and have an issue where there is a & in my link description text. ie this is taken from the source <a class='tag' href='/php/iphone software.php?function=developer&amp;dev=witch%26wizards+inc.&amp;store=143441'>witch&wizards inc.</a> Which gives me this error in the validator Line 188, Column 540: cannot generate system identifier for general entity "wizards" …6wizards+inc.&store=143441'witch&wizards inc. If I urlencode the description then the validation passes, but the user then sees the text displayed urlencoded, ie Developer witch%26wizards+inc. However I believe it's much more user friendly if this was displayed unencoded, ie Developer witch&wizards inc. Is there a way to pass validation but still have user friendly text displayed? Thanks, Greg

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• Another Java vs. Scala perspective - is this typical?

  - by Alex R

  I have been reading about Scala for a while and even wrote some small programs to better understand some of the more exoteric features. Today I decided to do my first "real project", translating some 60 lines of ugly Java code to Scala to rewrite it using the better pattern-matching features (why? because the Java version was becoming hard to maintain due to excessive combination of regex and conditionals). About halfway through the editing process, Eclipse thew up this error: I get the general impression that the Scala IDE in Eclipse is a lot buggier and less complete than its Java equivalent. Is this correct or do I just have a bad installation? Is there a better IDE for Scala?

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• How do I sum up weighted arrays in PHP?

  - by christian studer

  Hod do I multiply the values of a multi-dimensional array with weigths and sum up the results into a new array in PHP or in general? The boring way looks like this: $weights = array(0.25, 0.4, 0.2, 0.15); $values = array ( array(5,10,15), array(20,25,30), array(35,40,45), array(50,55,60) ); $result = array(); for($i = 0; $i < count($values[0]); ++$i) { $result[$i] = 0; foreach($weights as $index => $thisWeight) $result[$i] += $thisWeight * $values[$index][$i]; } Is there a more elegant solution?

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• Synchronising local and remote DB

  - by nico

  Hi everyone, I have a general question about DB synchronisation. So, I'm developing a website locally (PHP + MySQL) and I would like to be able to synchronise at least the structure (and maybe the contents) of the two DB when one of the two is changed (normally I would change the local copy). Right now what I'm doing is to use mysqldump to dump the modified tables and then import them in the remote DB or do it by hand if the changes are minimal. However I find this tedious and error-prone. For the PHP I'm currently using Quanta+ which has the handy feature of finding files that have changed and just upload those. Is there something similar for MySQL? Otherwise how do you keep your DBs synchronised? Thanks nico PS: I'm sorry if this was already asked, I saw other questions that deal with similar topics, but couldn't really find an answer.

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• Is frameworks really necessary for this problem?

  - by The Elite Gentleman

  Hi Guys I'm creating an online music store application (in Java) for signed and unsigned artist for my client. I'm currently using Struts 1.3.10 (I was recommended Spring but Spring setup is sort of similar to Struts) for my Web application. My Database is currently a MySQL 5 (or higher) and I'm using a DAO pattern to talk to it. There are limitations to using Struts and DAO's (e.g. Multiple File upload in Struts is not implemented the same way as multiple String parameters, and for DAO's, there lacks a Publish-Subscribe feature). Is what I'm doing the best way forward or should I go straight Hibernate (or similar) and move out of Struts? What are the performance implications or technical issues that you've experienced with the same setup I have? The client doesn't care how I do it as long as it is done.

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• .Net Logger (Write your own vs log4net/enterprise logger/nlog etc.)

  - by Jack

  I work for an IT department with about 50+ developers. It used to be about 100+ developers but was cut because of the recession. When our department was bigger there was an ambitious effort made to set up a special architecture group. One thing this group decided to do was create our own internal logger. They thought it was such a simple task that we could spend recources and do it ourselves. Now we are having issues with performance and difficulty viewing the logs generated and some employees are frustrated that we are spending recources on infrastructure stuff like this instead of focusing on serving our business and using stuff that already exists like log4net or Enterprise Logger. Can you assist me in listing up reasons why you should not create your own .net logger. Also reasons for why you should are welcome to get a fair point of view :)

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• Efficiency of while(true) ServerSocket Listen

  - by Submerged

  I am wondering if a typical while(true) ServerSocket listen loop takes an entire core to wait and accept a client connection (Even when implementing runnable and using Thread .start()) I am implementing a type of distributed computing cluster and each computer needs every core it has for computation. A Master node needs to communicate with these computers (invoking static methods that modify the algorithm's functioning). The reason I need to use sockets is due to the cross platform / cross language capabilities. In some cases, PHP will be invoking these java static methods. I used a java profiler (YourKit) and I can see my running ServerSocket listen thread and it never sleeps and it's always running. Is there a better approach to do what I want? Or, will the performance hit be negligible? Please, feel free to offer any suggestion if you can think of a better way (I've tried RMI, but it isn't supported cross-language. Thanks everyone

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• Algorithms to find longest common prefix in a sliding window.

  - by nn

  Hi, I have written a Lempel Ziv compressor and decompressor. I am seeking to improve the time to search the dictionary for a phrase. I have considered K-M-P and Boyer-Moore, but I think an algorithm that adapts to changes in the dictionary would be faster. I've been reading that binary search trees (AVL or with splays) improve the performance of compression time considerably. What I fail to understand is how to bootstrap the binary search tree and insert/remove data. I'm not actually quite sure the significance of each node in the binary search. I am searching for phrases so will each character be considered a node? Also how and what is inserted/removed from the search tree as new data enters the dictionary and old data is removed? The binary search tree sounds like a good payoff since it can adapt to the dictionary, but I'm just not quite sure of how it's used.

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• What are the best uses for each programming language?

  - by VirtuosiMedia

  I come from a web developer background, so I'm fairly familiar with PHP and JavaScript, but I'd eventually like to branch out into other languages. At this point, I don't have a particular direction or platform that I'm leaning toward as far as learning a new language or what I would use it for, but I would like to learn a little bit more about programming languages in general and what each one is used for. I've often heard (and I agree) that you should use the right tool for the job, so what jobs are each programming language best suited for? Edit: If you've worked with some of the newer or more obscure languages, please share for those as well.

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• Is it safe to catch an access violation in this scenario?

  - by Eloff

  I've read a lot, including here on SO that suggests this is a very bad idea in general and that the only thing you can do safely is exit the program. I'm not sure that this is true. This is for a pooling memory allocator that hands off large allocations to malloc. During pool_free() a pointer needs to be checked it it belongs to a pool or was allocated with malloc. By rounding the address down to the nearest 1MB boundary, I get a pointer to the beginning of a block of memory in the pool, or undefined if malloc was used. In the first case I can easily verify that the block of memory belongs to the pool, but, if it does not I will either fail this verification, or I will get an access violation (note that this is a read-only process). Could I not catch this with SEH (Windows) or handle the signal (POSIX) and simply treat it as a failed verification? (i.e. this is only possible if malloc was used, so pass the ptr to free())

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• Does the .NET CLR Really Optimize for the Current Processor

  - by dewald

  When I read about the performance of JITted languages like C# or Java, authors usually say that they should/could theoretically outperform many native-compiled applications. The theory being that native applications are usually just compiled for a processor family (like x86), so the compiler cannot make certain optimizations as they may not truly be optimizations on all processors. On the other hand, the CLR can make processor-specific optimizations during the JIT process. Does anyone know if Microsoft's (or Mono's) CLR actually performs processor-specific optimizations during the JIT process? If so, what kind of optimizations?

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• Need help converting apache .htaccess code to lighttpd url_rewrite code

  - by miCRoSCoPiC_eaRthLinG

  Hi All, I have this custom written CMS built on XAMPP. I'm trying to test the same on lighttpd to benchmark the so-called performance gains... but am stuck at the rewrite rules. I use the default rewrite rules of WordPress in my .htaccess which hands all url parsing over to my script as long as there aren't any files or directories same as the URL structure. Here's the code: RewriteBase /somedir/ # Let the Script handle all pretty URLs RewriteCond %{SCRIPT_FILENAME} !-d RewriteCond %{SCRIPT_FILENAME} !-f RewriteRule .* index.php [L] Can anyone please help me translate the same to the lighttpd format? I could only (partially) figure out the last line myself going through the lighty docs ... i.e. url.rewrite-once = ( ".*" => "index.php" ) But that of course won't suffice... All my CMS is doing is giving me 404's. Thanks, miCRoSCoPiC^eaRthLinG

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• Interesting interview question. .Net

  - by rahul

  Coding Problem NumTrans There is an integer K. You are allowed to add to K any of its divisors not equal to 1and K. The same operation can be applied to the resulting number and so on. Notice that starting from the number 4, we can reach any composite number by applying several such operations. For example, the number 24 can be reached starting from 4 using 5 operations: 468121824 You will solve a more general problem. Given integers n and m, return the minimal number of the described operations necessary to transform n into m. Return -1 if m can't be obtained from n. Definition Method signature: int GetLeastCount (int n, int m) Constraints N will be between 4 and 100000, inclusive. M will be between N and 100000, inclusive. Examples 1) 4 576 Returns: 14 The shortest order of operations is: 468121827365481108162243324432576 2) 8748 83462 Returns: 10 The shortest order of operations is: 874813122196832624439366590497873283106834488346083462 3) 4 99991 Returns: -1 The number 99991 can't be obtained because it’s prime!

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• turning open source software into a consulting business ?

  - by sofreakinghigh

  just some general and specific questions about running a business which uses open source software and sells training, services, and other value added solutions utilizing the open source asset(s). 1) how much modification do you need to make to an existing open source software/framework to give a new brand ? open source (GPLv3) branding issues here.... for ex) Mambo and Joomla, i think they are pretty much same ? but they have different labels. 2) Is there a disadvantage of promoting open source software/framework/suite in hopes of selling value added services and solutions on top of the Open source asset ? 3) can Open source assets be marketing point for lowered Total Ownership Cost and transparency ? meaning, clients will not be using some mysterious, opaque proprietary asset ? 4) is competition fierce? cost of developing software is non existing because you are using an open source asset. barrier to entry is minimal ??

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