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  • What does this xkcd code do?

    - by cobbal
    On the xkcd site today, the following appeared as a joke in a <script language="scheme"> tag so what does the following code do / represent? (define (eval exp env) (cond ((self-evaluating? exp) exp) ((variable? exp) (lookup-variable-value exp env)) ((quoted? exp) (text-of-quotation exp)) ((assignment? exp) (eval-assignment exp env)) ((definition? exp) (eval-definition exp env)) ((if? exp) (eval-if exp env)) ((lambda? exp) (make-procedure (lambda-parameters exp) (lambda-body exp) env)) ((begin? exp) (eval-sequence (begin-actions exp) env)) ((cond? exp) (eval (cond->if exp) env)) ((application? exp) (apply (eval (operator exp) env) (list-of-values (operands exp) env))) (else (error "Common Lisp or Netscape Navigator 4.0+ Required" exp))))

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  • [PHP] Difference between normal and magic setters and getters

    - by Saif Bechan
    I am using a magic getter/setter class for my session variables, but I don't see any difference between normal setters and getters. The code: class session { public function __set($name, $value) { $_SESSION[$name] = $value; } public function __unset($name) { unset($_SESSION[$name]); } public function __get($name) { if(isset($_SESSION[$name])) { return $_SESSION[$name]; } } } Now the first thing I noticed is that I have to call $session->_unset('var_name') to remove the variable, nothing 'magical' about that. Secondly when I try to use $session->some_var this does not work. I can only get the session variable using $_SESSION['some_var']. I have looked at the PHP manual but the functions look the same as mine. Am I doing something wrong, or is there not really anything magic about these functions.

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  • Determining whether values can potentially match a regular expression, given more input

    - by Andreas Grech
    I am currently writing an application in JavaScript where I'm matching input to regular expressions, but I also need to find a way how to match strings to parts of the regular expressions. For example: var invalid = "x", potentially = "g", valid = "ggg", gReg = /^ggg$/; gReg.test(invalid); //returns false (correct) gReg.test(valid); //returns true (correct) Now I need to find a way to somehow determine that the value of the potentially variable doesn't exactly match the /^ggg$/ expression, BUT with more input, it potentially can! So for example in this case, the potentially variable is g, but if two more g's are appended to it, it will match the regular expression /^ggg$/ But in the case of invalid, it can never match the /^ggg$/ expression, no matter how many characters you append to it. So how can I determine if a string has or doesn't have potential to match a particular regular expression?

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  • Dynamically creating controls in MFC (Collection question)

    - by ProgramWriter
    Hello all, I have some custom control inside of which i should create radiobuttons or checkboxes. The count of child controls is available only at runtime (it loads some file from which it gets this count). So i need to create variable number of controls. Which collection i should use for this purpose? Solution 1: simply use std::vector (or CArray) - not suitable because i want use MFC (CButton). Of course i can Attach() and later Detach() handle to window each time i need this window, but it will give big overhead. Solution 2: use std::vector or CArray or CList or... In this case i take care about making 'new' and appropriate 'delete' when control is unneeded. I am forgetful :) MFC handle map contains pointer to CButton and i can't use simple CArray, because it will move my objects each time when his size will grow. ... and the question is: Which collection i should use for containing variable count of MFC control classes?

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  • How to test custom template tags in Django?

    - by Mark Lavin
    I'm adding a set of template tags to a Django application and I'm not sure how to test them. I've used them in my templates and they seem to be working but I was looking for something more formal. The main logic is done in the models/model managers and has been tested. The tags simply retrieve data and store it in a context variable such as {% views_for_object widget as views %} """ Retrieves the number of views and stores them in a context variable. """ # or {% most_viewed_for_model main.model_name as viewed_models %} """ Retrieves the ViewTrackers for the most viewed instances of the given model. """ So my question is do you typically test your template tags and if you do how do you do it?

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  • Track http domain referer

    - by tony noriega
    Can i track the http referer with javascript, and append a variable to the URL string to store into a dbase? or could i track a cookie that the user gets? (very layman's terms here, sorry) if http referrer is domain.com add to url '&referer=google' which should stay with them during their session. OR when a user clicks my Google adwords ad. they get a cookie with a referring domain in it. try to read that cookie, and append the same variable. any thoughts?

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  • Regarding Multiple Tab-Class

    - by Christine
    Hi! I've problem regarding GUI with one Menu and one Order Class. I've created a variable to store how many items have been selected in the Menu Class. private int totalSelected; The var totalSelected is live updated. It can be changed anytime depending on actionPerformed() function.(Exp: totalSelected will add up all the selected items) In the Order Class, how can I access to the live update variable totalSelected in order to retrieve the live update value? When I invoke getTotalSelected() function inside the Menu Class, I will only obtain a 0 value. Thanks for your help ^^!

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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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  • jaxb XmlAccessType: PROPERTY example

    - by Bjorn J
    I'm trying to use jaxb and want to use the 'XmlAccessType.PROPERTY' to let jaxb use getters/setters rather than variable directly, but get different errors depending on what I try, or the variable isn't set at all like I want. Any good link or pointer to a simple example? For example, the below makes the groupDefintion not to be set when parsing the xml document: @XmlAccessorType(javax.xml.bind.annotation.XmlAccessType.PROPERTY) public class E { private EGroup groupDefinition; public EGroup getGroupDefinition () { return groupDefinition; } @XmlAttribute public void setGroupDefinition (EGroup g) { groupDefinition = g; } }

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  • Mysql IN clause, php array

    - by robert knobulous
    I know that this has been asked and answered before, but for the life of me I cannot find where I am going wrong. My code is below. $backa = array("1", "7", "8", "9", "12"); $backaa = implode(",", $backa); /* code to create connection object $wkHook */ $getOpt=$wkHook->prepare("select movementId, movementName from Movement where movementId IN ($backaa) order by movementName asc"); $getOpt->execute(); $getOpt->store_result($id, $name); Every time I run this I get one of two errors depending upon how I use the $backaa variable. More often than not I get a call to a non-object error indicating that $getOpt is not a proper Mysql query. I have tried every fashion of quoting, bracketing, etc for the $backaa variable but it's just not working for me. What obvious thing am I missing?

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  • C# -Closure -Clarification

    - by nettguy
    I am learning C#.Can I mean closure as a construct that can adopt the changes in the environment in which it is defined. Example : List<Person> gurus = new List<Person>() { new Person{id=1,Name="Jon Skeet"}, new Person{id=2,Name="Marc Gravell"}, new Person{id=3,Name="Lasse"} }; void FindPersonByID(int id) { gurus.FindAll(delegate(Person x) { return x.id == id; }); } The variable id is declared in the scope of FindPersonByID() but t we still can access the local variable id inside the anonymous function (i.e) delegate(Person x) { return x.id == id; } (1) Is my understanding of closure is correct ? (2) What are the aditional advantages can we get from closures?

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  • Following PHP coding of Wisdom

    - by justjoe
    i read some wisdom like this : Programmers are encouraged to be careful when using by-reference variables since they can negatively affect the readability and maintainability of the code. i make my own solution, such as give suffix such as _ref in every by-reference variables. so, if i have a variable named as $files_in_root, then i will add suffix and changes it name into $files_in_root_ref. As far my knowledge goes, this is a good solution. So, here come the question Is there any best-practice on choosing suffix for by-reference variable in PHP coder world ? Or do you have any ? In general, how do we sustain readability and maintainability on PHP project with more then 3000 line of code ? I hope PHP coder world has unwritten aggrement for first question, cause it will help spot a pattern on any source code.

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  • Simple PHP Regex question

    - by Dave Kiss
    Hi all, I'd like to validate a field in a form to make sure it contains the proper formatting for a URL linking to a Vimeo video. Below is what I have in Javascript, but I need to convert this over to PHP (not my forte) Basically, I need to check the field and if it is incorrectly formatted, I need to store an error message as a variable.. if it is correct, i store the variable empty. // Parse the URL var PreviewID = jQuery("#customfields-tf-1-tf").val().match(/http:\/\/(www.vimeo|vimeo)\.com(\/|\/clip:)(\d+)(.*?)/); if ( !PreviewID ) { jQuery("#cleaner").html('<div id="vvqvideopreview"><?php echo $this->js_escape( __("Unable to parse preview URL. Please make sure it's the <strong>full</strong> URL and a valid one at that.", 'vipers-video-quicktags') ); ?></div>'); return; } The traditional vimeo url looks like this: http://www.vimeo.com/10793773 Thanks!

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  • Capistrano configuration

    - by Eli
    I'm having some issues with variable scope with the capistrano-ext gem's multistage module. I currently have, in config/deploy/staging.rb. set(:settings) { YAML.load_file("config/deploy.yml")['staging'] } set :repository, settings["repository"] set :deploy_to, settings["deploy_to"] set :branch, settings["branch"] set :domain, settings["domain"] set :user, settings["user"] role :app, domain role :web, domain role :db, domain, :primary => true My config/deploy/production.rb file is similar. This doesn't seem very DRY. Ideally, I think I'd like everything to be in the deploy.rb file. If there were a variable set with the current stage, everything would be really clean. UPDATE: I found a solution. I defined this function in deploy.rb: def set_settings(params) params.each_pair do |k,v| set k.to_sym, v end if exists? :domain role :app, domain role :web, domain role :db, domain, :primary => true end end Then my staging.rb file is just set_settings(YAML.load_file("config/deploy.yml")['staging'])

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  • Convert Double to String without precision loss in javascript

    - by holger
    I would like to convert a floating point variable to a string without losing any precision. I.e. I would like the string to have the same information as my floating point variable contains, since I use the output for further processing (even if it means that the string will be very long and readable). To put this more clearly, I would like to have functions for cyclic conversion var dA = 323423.23423423e4; var sA = toString(dA); var dnA = toDouble(sA); and I would like dnA and dA to be equal Thanks PS: Sources on the internet usually talk about how to round strings but I have not found information on exact representation. Also I am not interested in Arbitrary Precision calculations, I just need double precision floating point arithmetic.

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  • Ruby on rails link_to syntax

    - by mizipzor
    After following a tutorial Ive found. Im now redoing it again, without the scaffolding part, to learn it better. However, editing my \app\views\home\index.html.erb to contain: <h1>Rails test project</h1> <%= link_to "my blog", posts_path> I get an error: undefined local variable or method `posts_path' for #<ActionView::Base:0x4e1d954> Before I did this, I ran rake db:create, defined a migration class and ran rake db:migrate, everything without a problem. So the database should contain a posts table. But that link_to command cant seem to find posts_path. That variable (or is it even a function?) is probably defined through the scaffold routine. My question now is; how do I do that manually myself, define posts_path?

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  • Logging extra fields with Elmah Error Table?

    - by VJ
    I want to add my own session variable to elmah error log table and display it. I already have modified the source code and added the new fields to Error.cs and other fields but I don't know but when I assign an HttpContext.Current.Session["MyVar"].tostring() value to my field in the constructor it stops logging exceptions and does not log any exception. I just need to get the value of the session variable is there other way for this. I read a post which he added fields for the email but it does not say where exactly should I get the session value.

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  • Java static and thread safety or what to do

    - by Parhs
    I am extending a library to do some work for me. Here is the code: public static synchronized String decompile(String source, int flags,UintMap properties,Map<String,String> namesMap) { Decompiler.namesMap=namesMap; String decompiled=decompile(source,flags,properties); Decompiler.namesMap=null; return decompiled; } The problem is that namesMap is static variable. Is that thread safe or not? Because if this code runs concurently namesMap variable may change. What can I do for this?

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  • Correct syntax for php inside a feed request

    - by Simon Hume
    Hi guys, I have a very basic query string which passes a ID to a receiving page. On that page, I need to dynamically call the YouTube API, giving my playlistID. I'm having to use PHP for this, and it's a little out of my comfort zone, so hopefully someone can wade in with a quick fix for me. Here is my variable $playlist; And I need to replace the 77DC230FBBCE4D58 below with that variable. $feedURL = 'http://gdata.youtube.com/feeds/api/playlists/77DC230FBBCE4D58?v=2'; Any help, as always, greatly appreciated!

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  • Php sessions secure log in

    - by Doodle
    My question is about creating a secure log in routine. After comparing the user name and password to the stored values I set a session variable called logged to true. Then as the user surfs around the web page I just check the logged variable for true or false to determine if the user should have access. This is my first time creating something like this. Is this secure? I feel like there is something else that I should be doing to make sure that users are valid.

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  • How can I retain the editing in the tableView of the search result with UISearchDisplayController?

    - by wal
    I want to search a table in editing mode, but when I type a letter the variable tableView.editing is changed to NO. And when I cancel the search, the tableView.editing return to YES. I'd like to retain the editing YES in the result of the search. I put breakpoint in several methods. Until the filterContentForSearchText method, the variable is YES, but in the cellForRowAtIndexPath, it is NO. Image of the table in editing mode just before type a letter in the search bar. Image of the search Image of the table after the searching (editing mode again)

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  • How to get real Integer Overflows in Matlab/Octave

    - by marvin2k
    Hi there. I'm working on a verification-tool for some VHDL-Code in Matlab/Octave. Therefore I need datatypes which generate "real" overflows: intmax('int32') + 1 ans = -2147483648 Lateron, it would be helpfull if i can define the bitwidth of a variable... But that is not so important... When I build a C-like example, where a variable gets increased until it's smaller than zero, it spins forever and ever... test = int32(2^30); while (test > 0) test = test + int32(1); end Another approach i tried was a custom "overflow"-routine which was called everytime after a number is changed. This approach was painfully slow, not practicable and not working in all cases at all...

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  • Difference between normal and magic setters and getters

    - by Saif Bechan
    I am using a magic getter/setter class for my session variables, but I don't see any difference between normal setters and getters. The code: class session { public function __set($name, $value) { $_SESSION[$name] = $value; } public function __unset($name) { unset($_SESSION[$name]); } public function __get($name) { if(isset($_SESSION[$name])) { return $_SESSION[$name]; } } } Now the first thing I noticed is that I have to call $session->_unset('var_name') to remove the variable, nothing 'magical' about that. Secondly when I try to use $session->some_var this does not work. I can only get the session variable using $_SESSION['some_var']. I have looked at the PHP manual but the functions look the same as mine. Am I doing something wrong, or is there not really anything magic about these functions.

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  • Django view function design

    - by dragoon
    Hi, I have the view function in django that written like a dispatcher calling other functions depending on the variable in request.GET, like this: action = '' for act in ('view1', 'view2', 'view3', 'view4', ... ): if act in request.GET: action = act break ... if action == '': response = view0(request, ...) elif action == 'view1': response = view1(request, ...) elif action == 'view2': response = view2(request, ...) ... The global dispatcher function contains many variable initialization routines and these variables are then used in viewXX functions. So I feed that this is bad view design but I don't know how I can rewrite it?

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