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  • What is Ruby's analog to Python Metaclasses?

    - by Sean Copenhaver
    Python has the idea of metaclasses that, if I understand correctly, allow you to modify an object of a class at the moment of construction. You are not modifying the class, but instead the object that is to be created then initialized. Python (at least as of 3.0 I believe) also has the idea of class decorators. Again if I understand correctly, class decorators allow the modifying of the class definition at the moment it is being declared. Now I believe there is an equivalent feature or features to the class decorator in Ruby, but I'm currently unaware of something equivalent to metaclasses. I'm sure you can easily pump any Ruby object through some functions and do what you will to it, but is there a feature in the language that sets that up like metaclasses do? So again, Does Ruby have something similar to Python's metaclasses? Edit I was off on the metaclasses for Python. A metaclass and a class decorator do very similar things it appears. They both modify the class when it is defined but in different manners. Hopefully a Python guru will come in and explain better on these features in Python. But a class or the parent of a class can implement a __new__(cls[,..]) function that does customize the construction of the object before it is initialized with __init__(self[,..]).

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  • Javascript: Multiple mouseout events triggered

    - by Channel72
    I'm aware of the different event models in Javascript (the WC3 model versus the Microsoft model), as well as the difference between bubbling and capturing. However, after a few hours reading various articles about this issue, I'm still unsure how to properly code the following seemingly simple behavior: If I have an outer div and an inner div element, I want a single mouse-out event to be triggered when the mouse leaves the outer-div. When the mouse crosses from the inner-div to the outer-div, nothing should happen, and when the mouse crosses from the outer-div to the inner-div nothing should happen. The event should only fire if the mouse moves from the outer-div to the surrounding page. <div id="outer" style = "width:20em; height:20em; border:1px solid #F00" align = "center" onmouseout="alert('mouseout event!')" > <div id="inner" style = "width:18em; height:18em; border:1px solid #000"></div> </div> Now, if I place the "mouseout" event on the outer-div, two mouse-out events are fired when the mouse moves from the inner-div to the surrounding page, because the event fires once when the mouse moves from inner to outer, and then again when it moves from outer to the surrounding page. I know I can cancel the event using ev.stopPropagation(), so I tried registering an event handler with the inner-div to cancel the event propagation. However, this won't prevent the event from firing when the mouse moves from the outer-div to the inner-div. So, unless I'm overlooking something, it seems to me this behavior can't be accomplished without complex mouse-tracking functions. In the future, I plan to reimplement a lot of this code using a more advanced framework, like JQuery, but for now, I'm wondering if there is a simple way to implement the above behavior in regular Javascript.

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  • Why is execution-time method resolution faster than compile-time resolution?

    - by Felix
    At school, we about virtual functions in C++, and how they are resolved (or found, or matched, I don't know what the terminology is -- we're not studying in English) at execution time instead of compile time. The teacher also told us that compile-time resolution is much faster than execution-time (and it would make sense for it to be so). However, a quick experiment would suggest otherwise. I've built this small program: #include <iostream> #include <limits.h> using namespace std; class A { public: void f() { // do nothing } }; class B: public A { public: void f() { // do nothing } }; int main() { unsigned int i; A *a = new B; for (i=0; i < UINT_MAX; i++) a->f(); return 0; } Where I made A::f() once normal, once virtual. Here are my results: [felix@the-machine C]$ time ./normal real 0m25.834s user 0m25.742s sys 0m0.000s [felix@the-machine C]$ time ./virtual real 0m24.630s user 0m24.472s sys 0m0.003s [felix@the-machine C]$ time ./normal real 0m25.860s user 0m25.735s sys 0m0.007s [felix@the-machine C]$ time ./virtual real 0m24.514s user 0m24.475s sys 0m0.000s [felix@the-machine C]$ time ./normal real 0m26.022s user 0m25.795s sys 0m0.013s [felix@the-machine C]$ time ./virtual real 0m24.503s user 0m24.468s sys 0m0.000s There seems to be a steady ~1 second difference in favor of the virtual version. Why is this? Relevant or not: dual-core pentium @ 2.80Ghz, no extra applications running between two tests. Archlinux with gcc 4.5.0. Compiling normally, like: $ g++ test.cpp -o normal Also, -Wall doesn't spit out any warnings, either.

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  • Number Algorithm

    - by James
    I've been struggling to wrap my head around this for some reason. I have 15 bits that represent a number. The bits must match a pattern. The pattern is defined in the way the bits start out: they are in the most flush-right representation of that pattern. So say the pattern is 1 4 1. The bits will be: 000000010111101 So the general rule is, take each number in the pattern, create that many bits (1, 4 or 1 in this case) and then have at least one space separating them. So if it's 1 2 6 1 (it will be random): 001011011111101 Starting with the flush-right version, I want to generate every single possible number that meets that pattern. The # of bits will be stored in a variable. So for a simple case, assume it's 5 bits and the initial bit pattern is: 00101. I want to generate: 00101 01001 01010 10001 10010 10100 I'm trying to do this in Objective-C, but anything resembling C would be fine. I just can't seem to come up with a good recursive algorithm for this. It makes sense in the above example, but when I start getting into 12431 and having to keep track of everything it breaks down.

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  • Works in Firefox & Opera, but not in IE8

    - by Ai Pragma
    1) This issue involves just one html webpage, lets call it "ajax.html".2) I have AJAX functions in this webpage that work in both Firefox and IE8.3) I now attempt generating just the option values of a dropdown list of dates using my ajax functions, and it works in Firefox & Opera, but not IE8.4) The surrounding html code for the dropdown looks like this:<select name="entry_7_single" id="entry_7" onChange="Ajax_PhpResultsWithVar('./secure/db/SummaryCls.php','entry_8','dateval',this.value)"></select>The onchange call refers to an ajax function that successfully(both Firefox & IE8) populates a textarea(entry_8) with a description of an event associated with the date selected in this dropdown. 5) An onload call initiates the ajax function to generate the dropdown list values:<body class="ss-base-body" onLoad="OnLoadWebPage()">6) The js script that calls the ajax function is as follows:function OnLoadWebPage(){    Ajax_PhpResults('./secure/db/GenDateListCls.php','entry_7');}7) Since it works in Firefox, but not IE8, I throw the output of the ajax function into a Firefox large textbox and I get the following:<option selected value="8 JUN 2010">8 JUN 2010</option>                   <option value="9 JUN 2010">9 JUN 2010</option>                   <option value="10 JUN 2010">10 JUN 2010</option>                   <option value="11 JUN 2010">11 JUN 2010</option> 8 ) There are over a hundred generated but you get the gist of what the ajax function generates. Next I will list the PHP function that outputs the above dropdown values://///////////////////////////////////////////////////////////////////////////////////////////////////////<?phpinclude_once 'SPSQLite.class.php';include_once 'misc_funcs.php';class GenDateListCls {    var $dbName;    var $sqlite;        function GenDateListCls()    {        $this->dbName = 'accrsc.db';        $this->ConstructEventDates();    }        function ConstructEventDates()    {         $this->sqlite = new SPSQLite($this->dbName);         $todayarr = getdate();         $today = $todayarr[mday] . " " . substr($todayarr[month],0,3) . " " . $todayarr[year];                  $ICalDate = ChangeToICalDate($today);         $dateQuery = "SELECT dtstart from events where substr(dtstart,1,8) >= '" . $ICalDate . "';";         $this->sqlite->query($dateQuery);         $datesResult = $this->sqlite->returnRows();                      foreach (array_reverse($datesResult) as $indx => $row)         {                       $normDate = NormalizeICalDate(substr($row[dtstart],0,8));              if ($indx==0)              { ?>                 <option selected value=<?php echo('"' . $normDate . '"'); ?>><?php echo $normDate; ?></option><?php                               }                          else              {?>                  <option value=<?php echo('"' . $normDate . '"'); ?>><?php echo $normDate; ?></option><?php                                   }                       }                   $this->sqlite->close();     }}$dateList = new GenDateListCls();    ?>/////////////////////////////////////////////////////////////////////////////////////////////////////////////<<< I appreciate any assistance on this matter. Aipragma >>> My Background: To let you all know, I am a complete newbie to PHP, Ajax, & javascript, and learning it all on my own, no classes. My background is in Linux, Windows, C++, Java, VB,VBA,MS XML, & some html.

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  • Saving twice don't update my object in JDO

    - by Javi
    Hello I have an object persisted in the GAE datastore using JDO. The object looks like this: public class MyObject implements Serializable, StoreCallback { @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) @Extension(vendorName="datanucleus", key="gae.encoded-pk", value="true") private String id; @Persistent private String firstId; ... } As usually when the object is stored for the first time a new id value is generated for the identifier. I need that if I don't provide a value for firstId it sets the same value as the id. I don't want to solve it with a special getter which checks for null value in firstId and then return the id value because I want to make queries relating on firstId. I can do it in this way by saving the object twice (Probably there's a better way to do this, but I'll do it in this way until I find a better one). But it is not working. when I debug it I can see that result.firstId is set with the id value and it seems to be persisted, but when I go into the datastore I see that firstId is null (as it was saved the first time). This save method is in my DAO and it is called in another save method in the service annotated with @Transactional. Does anyone have any idea why the second object in not persisted properly? @Override public MyObject save(MyObject obj) { PersistenceManager pm = JDOHelper.getPersistenceManagerFactory("transactions-optional"); MyObject result = pm.makePersistent(obj); if(result.getFirstId() == null){ result.setFirstId(result.getId()); result = pm.makePersistent(result); } return result; } Thanks.

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  • Emulate domready event with a custom event (mootools)

    - by Rob
    I need to fire a one time only custom event that functions like the domready event, in that if new events are added after the event has occurred they are fired immediately. This is for some code that cannot execute until certain data and resources are initialized, so I want to do something like this: // I am including a script (loadResources.js) to load data and other resources, // when loadResources.js is done doing it's thing it will fire resourcesAreLoaded with: window.fireEvent('resourcesAreLoaded'); window.addEvent('resourcesAreLoaded', function() { // this is fine }); $('mybutton').addEvent('click', function() { window.addEvent('resourcesAreLoaded', function() { // this is not fine, because resourcesAreLoaded has already fired // by the time the button is clicked }); }); If possible I would like resourcesAreLoaded to function like domready, and execute the code immediately if the event has already fired: window.addEvent('testIsReady', function() { alert('firing test'); }); window.fireEvent('testIsReady'); window.addEvent('test', function() { // this will never execute unless I call fireEvent('testIsReady') again alert('test 2'); }); window.addEvent('domready', function() { alert('domready is firing'); }); window.addEvent('domready', function() { setTimeout(function() { alert('domready has already fired, so this is executed immediately'); }, 500); });

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  • How to build Graceful Degradation AJAX web page?

    - by Morgan Cheng
    I want to build web page with "Graceful Degradation". That is, the web page functions even javascript is disabled. Now I have to make design decision on the format of AJAX response. If javascript is disabled, each HTTP request to server will generate HTML as response. The browser refreshes with the returned HTML. That's fine. If javascript is enabled, each AJAX HTTP request to server will generate ... well, JSON or HTML. If it is HTML, it is easy to implement. Just have javascript to replace part of page with the returned HTML. And, in server side, not much code change is needed. If it is JSON, then I have to implement JSON-to-html logic in javascript again which is almost duplicate of server side logic. Duplication is evil. I really don't like it. The benefit is that the bandwidth usage is better than HTML, which brings better performance. So, what's the best solution to Graceful Degradation? AJAX request better to return JSON or HTML?

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  • How to record different authentication types (username / password vs token based) in audit log

    - by RM
    I have two types of users for my system, normal human users with a username / password, and delegation authorized accounts through OAuth (i.e. using a token identifier). The information that is stored for each is quite different, and are managed by different subsytems. They do however interact with the same tables / data within the system, so I need to maintain the audit trail regardless of whether human user, or token-based user modified the data. My solution at the moment is to have a table called something like AuditableIdentity, and then have the two types inheriting off that table (either in the single table, or as two seperate tables with 1 to 1 PK with AuditableIdentity. All operations would use the common AuditableIdentity PK for CreatedBy, ModifiedBy etc columns. There isn't any FK constraint on the audit columns, so any text can go in there, but I want an easy way to easily determine whether it was a human or system that made the change, and joining to the one AuditableIdentity table seems like a clean way to do that? Is there a best practice for this scenario? Is this an appropriate way of approaching the problem - or would you not bother with the common table and just rely on joins (to the two seperate un-related user / token tables) later to determine which user type matches which audit records?

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  • Setting Position of source and listener has no effect

    - by Ben E
    Hi Guys, First time i've worked with OpenAL, and for the life of my i can't figure out why setting the position of the source doesn't have any effect on the sound. The sounds are in stero format, i've made sure i set the listener position, the sound is not realtive to the listener and OpenAL isn't giving out any error. Can anyone shed some light? Create Audio device ALenum result; mDevice = alcOpenDevice(NULL); if((result = alGetError()) != AL_NO_ERROR) { std::cerr << "Failed to create Device. " << GetALError(result) << std::endl; return; } mContext = alcCreateContext(mDevice, NULL); if((result = alGetError()) != AL_NO_ERROR) { std::cerr << "Failed to create Context. " << GetALError(result) << std::endl; return; } alcMakeContextCurrent(mContext); SoundListener::SetListenerPosition(0.0f, 0.0f, 0.0f); SoundListener::SetListenerOrientation(0.0f, 0.0f, -1.0f); The two listener functions call alListener3f(AL_POSITION, x, y, z); Real vec[6] = {x, y, z, 0.0f, 1.0f, 0.0f}; alListenerfv(AL_ORIENTATION, vec); I set the sources position to 1,0,0 which should be to the right of the listener but it has no effect alSource3f(mSourceHandle, AL_POSITION, x, y, z); Any guidance would be much appreciated

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  • Just messed up a server misusing chown, how to execute it correctly?

    - by Jack Webb-Heller
    Hi! I'm moving from an old shared host to a dedicated server at MediaTemple. The server is running Plesk CP, but, as far as I can tell, there's no way via the Interface to do what I want to do. On the old shared host, running cPanel, I creative a .zip archive of all the website's files. I downloaded this to my computer, then uploaded it with FTP to the new host account I'd set up. Finally, I logged in via SSH, navigated to the directory the zip was stored in (something like var/www/vhosts/mysite.com/httpdocs/ and ran the unzip command on the file sitearchive.zip. This extracted everything just the fine. The site appeared to work just fine. The problem: When I tried to edit a file through FTP, I got Error - 160: Permission Denied. When I Get Info for the file I'm trying to edit, it says the owner and group is swimwir1. I attemped to use chown at this point to change owner - and yes, as you may be able to tell, I'm a little inexperienced in SSH ;) luckily the server was new, since the command I ran - chown -R newuser / appeared to mess a load of stuff up. The reason I used / on the end rather than /var/www/vhosts/mysite.com/httpdocs/ was because I'd already cded into their, so I presumed the / was relative to where I was working. This may be the case, I have no idea, either way - Plesk was no longer accessible, although Apache and things continued to work. I realised my mistake, and deciding it wasn't worth the hassle of 1) being an amateur and 2) trying to fix it, I just reprovisioned the server to start afresh. So - what do I do to change the owner of these files correctly? Thanks for helping out a confused beginner! Jack

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  • Standardizing a Release/Tools group on a specific language

    - by grahzny
    I'm part of a six-member build and release team for an embedded software company. We also support a lot of developer tools, such as Atlassian's Fisheye, Jira, etc., Perforce, Bugzilla, AnthillPro, and a couple of homebrew tools (like my Django release notes generator). Most of the time, our team just writes little plugins for larger apps (ex: customize workflows in Anthill), long-term utility scripts (package up a release for QA), or things like Perforce triggers (don't let people check into a specific branch unless their change description includes a bug number; authenticate against Active Directory instead of Perforce's internal passwords). That's about the scale of our problems, although we sometimes tackle something slightly more sizable. My boss, who is reasonably technical, has asked us to standardize on one or two languages so we can more easily substitute for each other. He's advocating bash scripts and Perl, due to their universality and simplicity. I can see his point--we mostly do "glue", so why not use "glue" languages rather than saddle ourselves with something designed for much larger projects? Since some of the tools we work with are Java-based, we do need to use something that speaks JVM sometimes. (The path of least resistance for these projects is BeanShell and Groovy.) I feel a tremendous itch toward language advocacy, but I'm trying to avoid saying "We should use Python 'cause I like it and Perl is gross." Instead, I'm trying to come up with a good approach to defining our problem set: what problems do we solve with scripts? Would we benefit from a library of common functions by our team, or are most of our projects more isolated? What is it reasonable to expect my co-workers to learn? What languages give us the most ease of development and ease of modification? Can you folks suggest some useful ways to approach this problem, both for my own thinking process and to help me facilitate some brainstorming among my coworkers?

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  • php & mySQL: Storing doc, xls, zip, etc. with limited access and archiving

    - by Devner
    Hi all, In my application, I have a provision for users to upload files like doc, xls, zip, etc. I would like to know how to store these files on my website and have only restricted people access it. I may have a group of people and let only these group access those uploaded files. I know that some may try to just copy the link to the document or the file and pass it to another (non-permitted) user and they can download it. So how can I prevent it? How can I check if the request to download the file was made by a legitimate user who has access to the file? The usernames of the group members are stored in the database along with the document name and location in the database so they can access it. But how do I prevent non-permitted users from being able to access that confidential data in all ways? With the above in mind, how do I store these documents? Do I store the documents in a blob column in the Database or just just let user upload to a folder and merely store the path to the file in the database? The security of the documents is of utmost importance. So any procedure that could facilitate this feature would definitely help. I am not into Object Oriented programming so if you have a simpler code that you would like to share with me, I would greatly appreciate it. Also how do I archive documents that are old? Like say there are documents that are 1 year old and I want to conserve my website space by archiving them but still make them available to the user when they need it. How do I go about this? Thank you.

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  • fullcalendar : updating option function callbacks after init

    - by Paul Maneesilasan
    Ok, so I have a problem with setting options whose values are callback functions when I try to set them after plugin initialization. I think this would be a common behavior, to dynamically set event callback after init'ing the calendar. Here is a snipit of code: $(document).ready(function() { $('#calendar').fullCalendar({ editable: false ,events:[{"title":"meeting.title","start":"2010-05-21 15:58:16 UTC"},{"title":"meeting.title","start":"2010-05-24 15:58:16", "url":"http://google.com"}] /* ,eventClick: function(event) { if (event.url) { window.open(event.url); return false; } } */ }); $('#calendar').fullCalendar('options', 'eventClick', function(event) { if (event.url) { window.open(event.url); return false; } }); }); You can see that I have setting the eventClick function as an init option commented out. If I do it that way, it works fine. However if I try to set it after the init, it doesn't work :( Is the some other way to do this? Or am I stuck with having to set the behavior upfront?

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  • Java: Match tokens between two strings and return the number of matched tokens

    - by Cryssie
    Need some help to find the number of matched tokens between two strings. I have a list of string stored in ArrayList (example given below): Line 0 : WRB VBD NN VB IN CC RB VBP NNP Line 1 : WDT NNS VBD DT NN NNP NNP Line 2 : WRB MD PRP VB DT NN IN NNS POS JJ NNS Line 3 : WDT NN VBZ DT NN IN DT JJ NN IN DT NNP Line 4 : WP VBZ DT JJ NN IN NN Here, you can see each string consists of a bunch of tokens separated by spaces. So, there's three things I need to work with.. Compare the first token (WRB) in Line 0 to the tokens in Line 1 to see if they match. Move on to the next tokens in Line 0 until a match is found. If there's a match, mark the matched tokens in Line 1 so that it will not be matched again. Return the number of matched tokens between Line 0 and Line 1. Return the distance of the matched tokens. Example: token NN is found on position 3 on line 0 and position 5 on Line 1. Distance = |3-5| = 2 I've tried using split string and store it to String[] but String[] is fixed and doesn't allow shrinking or adding of new elements. Tried Pattern Matcher but with disasterous results. Tried a few other methods but there's some problems with my nested for loops..(will post part of my coding if it will help). Any advice or pointers on how to solve this problem this would be very much appreciated. Thank you very much.

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  • Programming test for ASP.NET C# developer job - Opinions please!

    - by Indy
    Hi all, We are hiring a .NET C# developer and I have developed a technical test for the candidates to complete. They have an hour and it has two parts, some knowledge based questions covering asp.net, C# and SQL and a small practical test. I'd appreciate feedback on the test, is it sufficient to test the programmers ability? What would you change if anything? Part One. What the are events fired as part of the ASP.NET Page lifecycle. What interesting things can you do at each? How does ViewState work and why is it either useful or bad? What is a common way to create web services in ASP.NET 2.0? What is the GAC? What is boxing? What is a delegate? The C# keyword .int. maps to which .NET type? Explain the difference between a Stored Procedure and a Trigger? What is an OUTER Join? What is @@IDENTITY? Part Two: You are provided with the Northwind Database and the attached DB relationship diagram. Please create a page which provides users with the following functionality. You don’t need to be too concerned with the presentation detail of the page. Select a customer from a list, and see all the orders placed by that customer. For the same customer, find all their orders which are Beverages and the quantity is more than 5. I was aware of setting the right balance of difficulty on this as there is an hour's test. I was able to complete the practical test in under 30 mins using SQLDatasource and the query designer in visual studio and the test questions, I am looking to see how they approach it logically and whether they use the tools available. Many thanks!

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  • Understanding CSRF - Simple Question

    - by byronh
    I know this might make me seem like an idiot, I've read everything there is to read about CSRF and I still don't understand how using a 'challenge token' would add any sort of prevention. Please help me clarify the basic concept, none of the articles and posts here on SO I read seemed to really explicitly state what value you're comparing with what. From OWASP: In general, developers need only generate this token once for the current session. After initial generation of this token, the value is stored in the session and is utilized for each subsequent request until the session expires. If I understand the process correctly, this is what happens. I log in at http://example.com and a session/cookie is created containing this random token. Then, every form includes a hidden input also containing this random value from the session which is compared with the session/cookie upon form submission. But what does that accomplish? Aren't you just taking session data, putting it in the page, and then comparing it with the exact same session data? Seems like circular reasoning. These articles keep talking about following the "same-origin policy" but that makes no sense, because all CSRF attacks ARE of the same origin as the user, just tricking the user into doing actions he/she didn't intend. Is there any alternative other than appending the token to every single URL as a query string? Seems very ugly and impractical, and makes bookmarking harder for the user.

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  • How to suggest changes as a recently-hired employee ?

    - by ereOn
    Hi, I was recently hired in a big company (thousands of people, to give an idea of the size). They said they hired me because of my rigor and because I was, despite my youngness (i'm 25), experienced as a C/C++ programer. Now that I'm in, I can see that the whole system is old and often uses obsolete technologies. There is no naming convention (files, functions, variables, ...), they don't use Version Control, don't use exceptions or polymorphism and it seems like almost everybody lost his passion (some of them are only 30 years old). I'd like to suggest somes changes but i don't want to be "the new guy that wants to change everything just because he doesn't want to fit in". I tried to "fit in", but actually, It takes me one week to do what I would do in one afternoon, just because of the poor tools we're forced to use. A lot my collegues never look at the new "things" and techniques that people use nowadays. It's like they just given up. The situation is really frustrating. Have you ever been in a similar situation and, if so, what advices would you give me ? Is there a subtle way of changing things without becoming the black sheep here ? Or should I just give up my passion and energy as well ? Thank you.

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  • how do I make a portable isnan/isinf function.

    - by monkeyking
    I've been using isinf,isnan functions on linux platforms which worked perfectly. But this didn't work on osx, so I decided to use std::isinf std::isnan which works on both linux and osx. But the intel compiler doesn't recognize it, and I guess its a bug in the intel compiler according to http://software.intel.com/en-us/forums/showthread.php?t=64188 So now I just want to avoid the hassle and define my own isinf,isnan implementation. Does anyone know how this could be done Thanks edit: I ended up doing this in my sourcecode for making isinf/isnan working #include <iostream> #include <cmath> #ifdef __INTEL_COMPILER #include <mathimf.h> #endif int isnan_local(double x) { #ifdef __INTEL_COMPILER return isnan(x); #else return std::isnan(x); #endif } int isinf_local(double x) { #ifdef __INTEL_COMPILER return isinf(x); #else return std::isinf(x); #endif } int myChk(double a){ std::cerr<<"val is: "<<a <<"\t"; if(isnan_local(a)) std::cerr<<"program says isnan"; if(isinf_local(a)) std::cerr<<"program says isinf"; std::cerr<<"\n"; return 0; } int main(){ double a = 0; myChk(a); myChk(log(a)); myChk(-log(a)); myChk(0/log(a)); myChk(log(a)/log(a)); return 0; }

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  • Design suggestion for expression tree evaluation with time-series data

    - by Lirik
    I have a (C#) genetic program that uses financial time-series data and it's currently working but I want to re-design the architecture to be more robust. My main goals are: sequentially present the time-series data to the expression trees. allow expression trees to access previous data rows when needed. to optimize performance of the data access while evaluating the expression trees. keep a common interface so various types of data can be used. Here are the possible approaches I've thought about: I can evaluate the expression tree by passing in a data row into the root node and let each child node use the same data row. I can evaluate the expression tree by passing in the data row index and letting each node get the data row from a shared DataSet (currently I'm passing the row index and going to multiple synchronized arrays to get the data). Hybrid: an immutable data set is accessible by all of the expression trees and each expression tree is evaluated by passing in a data row. The benefit of the first approach is that the data row is being passed into the expression tree and there is no further query done on the data set (which should increase performance in a multithreaded environment). The drawback is that the expression tree does not have access to the rest of the data (in case some of the functions need to do calculations using previous data rows). The benefit of the second approach is that the expression trees can access any data up to the latest data row, but unless I specify what that row is, I'll have to iterate through the rows and figure out which one is the last one. The benefit of the hybrid is that it should generally perform better and still provide access to the earlier data. It supports two basic "views" of data: the latest row and the previous rows. Do you guys know of any design patterns or do you have any tips that can help me build this type of system? Should I use a DataSet to hold and present the data, or are there more efficient ways to present rows of data while maintaining a simple interface? FYI: All of my code is written in C#.

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  • mysql image disable print download

    - by Vish
    Hi, We use a Flex AIR client and a WAMP server. Tiff images are stored in MySQL. Currently, I can download the image from AIR client and it prompts for a download dialog. Things are fine till this point. We got a new requirement. Requirement is that only some users can print the image which gets downloaded. For other users, they should not be able to print the tiff image. Wondering how to accomplish this. One idea, not sure if its efficient, is to convert the image requested to pdf at the server side, disable print option there(hope there are API's available) and send back the pdf. Please let me know btter ideas. Also, is there a way to prevent file download dialog from popping up everytime the file is requested for download? Can we just get the file stream to the client and manipulate it to open with a particular viewer or write it to pdf... Please help.

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  • Connecting to SFTP service via Java Runtime process

    - by ohseekay
    Under my project, I have a Java class file, inside of which I have a routine which executes the following external SFTP script file: #!/bin/sh echo "cd AV/OASIS" >> sftp echo "put $1 $2" >> sftp echo "get AV/OASIS/$2 $3$2" >> sftp echo "bye" >> sftp /usr/local/bin/sftp -b sftp id@domain cat /dev/null > sftp exit 0 The Java code which executes the script file is as below: String script = "full path of script"; Process p = Runtime.getRuntime().exec(script + " " + param1 + " " + param2 + " " + param3); However, I'm not sure why, but the log generated by the class file always shows the error "Host key verification failed. Connection closed." I'd isolated that line in the script which connected to the remote machine, and ran it on the local machine (where this class file and script file are stored), and the command executed successfully I'd manually run the command which the Java class file will execute and it also tested okay: $ script.sh param1 param2 param3 I'd tried to look up the error message on the Internet, and apparently it seems to have something to do with known_hosts. Could this be the reason, or is there something else I'm missing? Thanks so much!

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  • iPhone static library Clang/LLVM error: non_lazy_symbol_pointers

    - by Bekenn
    After several hours of experimentation, I've managed to reduce the problem to the following example (C++): extern "C" void foo(); struct test { ~test() { } }; void doTest() { test t; // 1 foo(); // 2 } This is being compiled for iOS devices in XCode 4.2, using the provided Clang compiler (Apple LLVM compiler 3.0) and the iOS 5.0 SDK. The project is configured as a Cocoa Touch Static Library, and "Enable Linking With Shared Libraries" is set to No because I'm building an AIR native extension. The function foo is defined in another external library. (In my actual project, this would be any of the C API functions defined by Adobe for use in AIR native extensions.) When attempting to compile this code, I get back the error: FATAL:incompatible feature used: section type non_lazy_symbol_pointers (must specify "-dynamic" to be used) clang: error: assembler command failed with exit code 1 (use -v to see invocation) The error goes away if I comment out either of the lines marked 1 or 2 above, or if I change the build setting "Enable Linking With Shared Libraries" to Yes. (However, if I change the build setting, then I get multiple ld warning: unexpected srelocation type 9 warnings when linking the library into the final project, and the application crashes when running on the device.) The build error also goes away if I remove the destructor from test. So: Is this a bug in Clang? Am I missing some all-important and undocumented build setting? The interaction between an externally-provided function and a struct with a destructor is very peculiar, to say the least.

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  • Chord Chart - Skip to key with a click

    - by Juan Gonzales
    I have a chord chart app that basically can transpose a chord chart up and down throughout the keys, but now I would like to expand that app and allow someone to pick a key and automatically go to that key upon a click event using a function in javascript or jquery. Can someone help me figure this out? The logic seems simple enough, but I'm just not sure how to implement it. Here are my current functions that allow the user to transpose up and down... var match; var chords = ['C','C#','D','D#','E','F','F#','G','G#','A','A#','B','C','Db','D','Eb','E','F','Gb','G','Ab','A','Bb','B','C']; var chords2 = ['C','Db','D','Eb','E','F','Gb','G','Ab','A','Bb','B','C','C#','D','D#','E','F','F#','G','G#','A','A#','C']; var chordRegex = /(?:C#|D#|F#|G#|A#|Db|Eb|Gb|Ab|Bb|C|D|E|F|G|A|B)/g; function transposeUp(x) { $('.chord'+x).each(function(){ ///// initializes variables ///// var currentChord = $(this).text(); // gatheres each object var output = ""; var parts = currentChord.split(chordRegex); var index = 0; ///////////////////////////////// while (match = chordRegex.exec(currentChord)){ var chordIndex = chords2.indexOf(match[0]); output += parts[index++] + chords[chordIndex+1]; } output += parts[index]; $(this).text(output); }); } function transposeDown(x){ $('.chord'+x).each(function(){ var currentChord = $(this).text(); // gatheres each object var output = ""; var parts = currentChord.split(chordRegex); var index = 0; while (match = chordRegex.exec(currentChord)){ var chordIndex = chords2.indexOf(match[0],1); //var chordIndex = $.inArray(match[0], chords, -1); output += parts[index++] + chords2[chordIndex-1]; } output += parts[index]; $(this).text(output); }); } Any help is appreciated. Answer will be accepted! Thank You

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  • How to recalculate all-pairs shorthest paths on-line if nodes are getting removed?

    - by Pavel Shved
    Latest news about underground bombing made me curious about the following problem. Assume we have a weighted undirected graph, nodes of which are sometimes removed. The problem is to re-calculate shortest paths between all pairs of nodes fast after such removals. With a simple modification of Floyd-Warshall algorithm we can calculate shortest paths between all pairs. These paths may be stored in a table, where shortest[i][j] contains the index of the next node on the shortest path between i and j (or NULL value if there's no path). The algorithm requires O(n³) time to build the table, and eacho query shortest(i,j) takes O(1). Unfortunately, we should re-run this algorithm after each removal. The other alternative is to run graph search on each query. This way each removal takes zero time to update an auxiliary structure (because there's none), but each query takes O(E) time. What algorithm can be used to "balance" the query and update time for all-pairs shortest-paths problem when nodes of the graph are being removed?

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