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  • Avoiding explicit recursion in Haskell

    - by Travis Brown
    The following simple function applies a given monadic function iteratively until it hits a Nothing, at which point it returns the last non-Nothing value. It does what I need, and I understand how it works. lastJustM :: (Monad m) => (a -> m (Maybe a)) -> a -> m a lastJustM g x = g x >>= maybe (return x) (lastJustM g) As part of my self-education in Haskell I'm trying to avoid explicit recursion (or at least understand how to) whenever I can. It seems like there should be a simple non-explicitly recursive solution in this case, but I'm having trouble figuring it out. I don't want something like a monadic version of takeWhile, since it could be expensive to collect all the pre-Nothing values, and I don't care about them anyway. I checked Hoogle for the signature and nothing shows up. The m (Maybe a) bit makes me think a monad transformer might be useful here, but I don't really have the intuitions I'd need to come up with the details (yet). It's probably either embarrassingly easy to do this or embarrassingly easy to see why it can't or shouldn't be done, but this wouldn't be the first time I've used self-embarrassment as a pedagogical strategy. Background: Here's a simplified working example for context: suppose we're interested in random walks in the unit square, but we only care about points of exit. We have the following step function: randomStep :: (Floating a, Ord a, Random a) => a -> (a, a) -> State StdGen (Maybe (a, a)) randomStep s (x, y) = do (a, gen') <- randomR (0, 2 * pi) <$> get put gen' let (x', y') = (x + s * cos a, y + s * sin a) if x' < 0 || x' > 1 || y' < 0 || y' > 1 then return Nothing else return $ Just (x', y') Something like evalState (lastJustM (randomStep 0.01) (0.5, 0.5)) <$> newStdGen will give us a new data point.

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  • jQuery - Animation flicker using hover()

    - by Chris
    I have a setup as described in this question which works perfectly. Essentially a drop down menu grows when you move your mouse over it to expose more options. There is, however, a small issue. If you move the mouse outside of the #dropdown div and then back in again quickly it constantly fires the mouseenter and mouseleave events causing a never ending cycle of flickering. How can I get around it? Here is my current jQuery code $("#dropdown").hover(function() { $(this).stop(true,true).fadeTo('fast',1); $("#options").stop(true,true).slideDown(); }, function() { $(this).stop(true,true).fadeTo('fast',0.1); $("#options").stop(true,true).slideUp(); } );

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  • How do I use Declarations (type, inline, optimize) in Scheme?

    - by kunjaan
    How do I declare the types of the parameters in order to circumvent type checking? How do I optimize the speed to tell the compiler to run the function as fast as possible like (optimize speed (safety 0))? How do I make an inline function in Scheme? How do I use an unboxed representation of a data object? And finally are any of these important or necessary? Can I depend on my compiler to make these optimizations? thanks, kunjaan.

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  • Scalable way of doing self join with many to many table

    - by johnathan
    I have a table structure like the following: user id name profile_stat id name profile_stat_value id name user_profile user_id profile_stat_id profile_stat_value_id My question is: How do I evaluate a query where I want to find all users with profile_stat_id and profile_stat_value_id for many stats? I've tried doing an inner self join, but that quickly gets crazy when searching for many stats. I've also tried doing a count on the actual user_profile table, and that's much better, but still slow. Is there some magic I'm missing? I have about 10 million rows in the user_profile table and want the query to take no longer than a few seconds. Is that possible?

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  • Override default javascript functionality with jQuery

    - by deth4uall
    I am trying to overwrite a JavaScript on change event in the below code with jQuery however I believe that the inline JavaScript is taking priority over the jQuery functionality declared. Essentially I am trying to have an AJAX version of my site which includes an additional JavaScript file. I need this functionality to still work without the additional AJAX version, but I am not sure as to whether I should include it in the main JavaScript file or leave it inline like it is right now. Any suggestions and information regarding them would be greatly appreciated! Thanks! <form action="/cityhall/villages/" method="post" name="submit_village"> <select name="village" onchange="document.submit_village.submit();"> <option value=""></option> </select> </form> I am trying to use the jQuery Form Plugin to submit the posts to the PHP to handle the requests as follows: var bank_load_options = { target: '#content', beforeSubmit: showRequest, success: showResponse }; $('form.get_pages').livequery(function(){ $(this).ajaxForm(bank_load_options); return false; }); I modified the code as following: <form action="/cityhall/villages/" method="post" id="submit_village" name="submit_village"> <select name="village" class="get_pages" rel="submit_village"> <option value=""></option> </select> </form> <script> # main JavaScript $('.get_pages').live('change',function(e){ var submit_page = $(this).attr('rel'); $("#"+submit_page).submit(); }); # ajax JavaScript var bank_load_options = { target: '#content', beforeSubmit: showRequest, success: showResponse }; $('.get_pages').live('change',function(){ var submit_page = $(this).attr('rel'); $("#"+submit_page).ajaxForm(get_pages_load_options); return false; }); </script> However now it only runs every other option when I change it.

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  • make a lazy var in scala

    - by ayvango
    Scala does not permit to create laze vars, only lazy vals. It make sense. But I've bumped on use case, where I'd like to have similar capability. I need a lazy variable holder. It may be assigned a value that should be calculated by time-consuming algorithm. But it may be later reassigned to another value and I'd like not to call first value calculation at all. Example assuming there is some magic var definition lazy var value : Int = _ val calc1 : () => Int = ... // some calculation val calc2 : () => Int = ... // other calculation value = calc1 value = calc2 val result : Int = value + 1 This piece of code should only call calc2(), not calc1 I have an idea how I can write this container with implicit conversions and and special container class. I'm curios if is there any embedded scala feature that doesn't require me write unnecessary code

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  • get content of a div from a variable using jQuery

    - by devdarsh
    i am building a php form with ajax and i am submitting the form variables to the same page where the form resides. my validating code looks like if($valid){ echo "<div id='retmsg'>Your message has been submitted successfully</div>"; } else { echo "<div id='retmsg'>An error occured!</div>"; } My ajax code function form_submit() { $('#response').html('Loading...').fadeIn(); $.ajax({ type: "POST", url: "<?php $_SERVER['PHP_SELF']; ?>", data: "title=" + $('#title').val() + "&content=" + $('#contents').val(), success: function(html){ var message = $("#retmsg").html(html); alert(message); } }); } i need to alert the contents of div id "retmsg". But the alert shows me like "[Object Object]". Please help me...

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  • Submiting a form from ajax outside the page (php)

    - by peter
    hey i use jquery to insert a form into a div, the form is in a php file. function show(id){ var content = $("#layer1_content"); $("#layer1").show(); var targetUrl = "mouse.php?cat="+id; content.load(targetUrl); } so everything works, but when i submit it goes too that php page, if i call the same form within the same php then it works fine. the response is handled by: $('#layer1_form').ajaxForm({ target: '#content', success: function() { $("#layer1").hide(); } });

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  • is it possible to override a css class

    - by oo
    i have the following jquery code to format a html table. $(".jtable td").each(function() { $(this).addClass("ui-widget-content"); }); i want (one on table) to change the text color to blue (its black in the ui-widget-content class. i tried doing this below but it didn't seem to do anything. Any help on override some particular css for one table (and i want to leave the other tables alone) $(".jtable td").each(function() { $(this).addClass("ui-widget-content"); $(this).css("color", "Blue"); });

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  • VS 2010 Entity Repository Error

    - by Steve
    In my project I have it set up so that all the tables in the DB has the property "id" and then I have the entity objects inherit from the EntityBase class using a repository pattern. I then set the inheritance modifier for "id" property in the dbml file o/r designer to "overrides" Public MustInherit Class EntityBase MustOverride Property id() As Integer End Class Public MustInherit Class RepositoryBase(Of T As EntityBase) Protected _Db As New DataClasses1DataContext Public Function GetById(ByVal Id As Integer) As T Return (From a In _Db.GetTable(Of T)() Where a.id = Id).SingleOrDefault End Function End Class Partial Public Class Entity1 Inherits EntityBase End Class Public Class TestRepository Inherits RepositoryBase(Of Entity1) End Class the line Return (From a In _Db.GetTable(Of T)() Where a.id = Id).SingleOrDefault however produces the error "Class member EntityBase.id is unmapped" when i use VS 2010 using the 4.0 framework but I never received that error with the old one. Any help would be greatly appreciated. Thanks in advance.

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  • Pause auto-rotate on mouseover (jQuery)

    - by Nimbuz
    I'm using a content slider plugin that is nice but lacks one important feature: does not stop auto-rotating slides on mouseover. Here's the relevant part from the script: var dotimer = function (x){ if((opts.auto) == true) { if(timer != null) clearInterval(timer); timer = setInterval(function() { $(opts.next).click(); }, 3000); } } dotimer(); Full script can be previewed here I want the rotation to pause on mouseover and resume on mouseout. Thanks in advance for your help!

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  • Jquery mobile spinner not loading in external links

    - by Jorge Zuverza
    I'm developing an application in which I have internal and external links. i noticed that Jquery mobile does not load the spinner when an external link is clicked: Example <a href = "/products">Spinner is shown </a> <a href = "othersite.com" rel = "external">Spinner is NOT shown </a> I have tried : $('a[href][rel=external]').click(function(){ //doesnt work $.mobile.showPageLoadingMsg(); } and: $('a[href][rel=external]').click(function(){ // shows the spinner but it gets stuck forever $.mobile.showPageLoadingMsg(); $('#loadingDiv').div("refresh"); } can someone help me show the spinner when the rel = external links are clicked? thanks!

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  • $("body").scrollTop() doesn't update in safari

    - by Kristoffer Nolgren
    I'm working on a website: http://beta.projektopia.se/ the body has several background-images that are updated on scroll like this: $(document).ready(function(){ $(document).scroll(function(){ var scrollfactor=$("body").scrollTop()*0.2; var centerscrollpos =scrollfactor+613; var docheight = $(document).height(); var windowheight = $(window).height(); var bottompos = (docheight-980)-((docheight-windowheight)*0.2)+scrollfactor; var scrollpos = 'center '+scrollfactor+'px,center '+bottompos+'px, center '+ centerscrollpos+'px,center 0px'; $("body").css("background-position", scrollpos); }); }); Lots of calculations, but the important thing is that a scrollpos is created that should change the position of the background when you scroll, to create a parallax-effect. It works great in chrome, but in firefox, the variable scrollfactor, that is suppose to get the current scroll-position, doesn't update. ps, some people have this issue due to lack of correct doctype. I believe i have declared it correctly like this: <!DOCTYPE html>

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  • C++: Template functor cannot deduce reference type

    - by maciekp
    I've got a functor f, which takes a function func and a parameter t of the same type as func. I cannot pass g to f because of compilation error (no matching function for call to f(int&, void (&)(int&)) ). If g would take non-reference parameter g(int s), compilation finishes. Or if I manually specify template parameter f(i, g), compilation also finishes. template<typename T> void f(T t, void (*func)(T)) {} void g(int& s) {} int main(int, char*[]) { int i = 7; f(i, g); // compilation error here return 0; } How can I get deduction to work?

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  • iPhone NSMutableDictionary setObject forKey after initWithContentsOfFile

    - by andrew
    so here's my function + (void) AddAddress:(NSString*)ip:(NSString*)mac { NSMutableDictionary* currentAddresses = [[NSMutableDictionary alloc] initWithContentsOfFile:[self filePath:ADDRESSES_FILE]]; [currentAddresses setObject:mac forKey:ip]; [Configuration Write:currentAddresses]; [currentAddresses release]; } [self filePath:ADDRESSES_FILE] returns a string containing the full path of a file (ADDRESSES_FILE) located in the Documents. The file may not exist, in this case I want to just write an object to the dictionary and then write it down the problem is that when i do setObject forKey it doesn't add anything to the dict (if i just do alloc init to the dict, it works fine, but i want to read the records from the file, if there are any, and replace/add a record by using the AddAddress function)

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  • Why is JSON outputting out of order?

    - by dcp3450
    I'm am trying to get a list of weather information for 8 locations. I'm using a weather API that accepts longitude and latitude and spits back json output with the weather info for that location. I feed the coords in order 0-7 but when json processes the data it comes back in a seemingly random order. I assume it's because some process faster than others and json is outputing what it gets back as it gets it. The output is correct, only the order is wrong. var loc = null; var body = ""; var campuses = new Array(8); campuses[0] = "34.47242,-84.42489,1"; campuses[1] = "33.81488,-84.62048,2"; campuses[2] = "34.27502,-84.46976,3"; campuses[3] = "33.92987,-84.55065,4"; campuses[4] = "34.03433,-84.46723,5"; campuses[5] = "34.08362,-84.67115,6"; campuses[6] = "33.91124,-84.82634,7"; campuses[7] = "34.10409,-84.51804,8"; function getWeather(campusArray) { body += '<p class="topTitle">Campus Weather</p>'; var cSplit = new Array(); cSplit = campusArray.split(','); var loc = "http://www.worldweatheronline.com/feed/weather.ashx?q="+cSplit[0]+","+cSplit[1]+"&format=json&num_of_days=2&key=0a05fff921162948110401&callback=?"; $('#content').html('asdf'); $.getJSON(loc,function(js) { var data = js.data; var humidity = data.current_condition[0].humidity; var tempF = data.current_condition[0].temp_F; var iconDESC = data.current_condition[0].weatherDesc[0].value; var iconURL = data.current_condition[0].weatherIconUrl[0].value; var windDir = data.current_condition[0].winddir16Point; var windSpeed = data.current_condition[0].windspeedMiles; var tempMaxF = data.weather[0].tempMaxF; var tempMinF = data.weather[0].tempMinF; body += '<p class="title">'+cSplit[2]+'</p>'+ '<span class="body">'+tempF+ ' '+windSpeed+ '<img src="'+iconURL+'" /></span>'; $('#content').html(body); }); } getWeather(campuses[0]); getWeather(campuses[1]); getWeather(campuses[2]); getWeather(campuses[3]); getWeather(campuses[4]); getWeather(campuses[5]); getWeather(campuses[6]); getWeather(campuses[7]); I have also tried it as $.ajax var loc = null; var body = ""; var campuses = new Array(8); campuses[0] = "34.47242,-84.42489,1"; campuses[1] = "33.81488,-84.62048,2"; campuses[2] = "34.27502,-84.46976,3"; campuses[3] = "33.92987,-84.55065,4"; campuses[4] = "34.03433,-84.46723,5"; campuses[5] = "34.08362,-84.67115,6"; campuses[6] = "33.91124,-84.82634,7"; campuses[7] = "34.10409,-84.51804,8"; function getWeather(campusArray) { body += '<p class="topTitle">Campus Weather</p>'; var cSplit = new Array(); cSplit = campusArray.split(','); var loc = "http://www.worldweatheronline.com/feed/weather.ashx?q="+cSplit[0]+","+cSplit[1]+"&format=json&num_of_days=2&key=0a05fff921162948110401&callback=?"; $.ajax({ url: loc, async: true, dataType: "json", success: function(js) { var data = js.data; var humidity = data.current_condition[0].humidity; var tempF = data.current_condition[0].temp_F; var iconDESC = data.current_condition[0].weatherDesc[0].value; var iconURL = data.current_condition[0].weatherIconUrl[0].value; var windDir = data.current_condition[0].winddir16Point; var windSpeed = data.current_condition[0].windspeedMiles; var tempMaxF = data.weather[0].tempMaxF; var tempMinF = data.weather[0].tempMinF; body += '<p class="title">'+cSplit[2]+'</p>'+ '<span class="body">'+tempF+ ' '+windSpeed+ '<img src="'+iconURL+'" /></span>'; $('#content').html(body); } }); } getWeather(campuses[0]); getWeather(campuses[1]); getWeather(campuses[2]); getWeather(campuses[3]); getWeather(campuses[4]); getWeather(campuses[5]); getWeather(campuses[6]); getWeather(campuses[7]); EDIT: example of json output: { "data": { "current_condition": [ {"cloudcover": "100", "humidity": "93", "observation_time": "04:04 PM", "precipMM": "0.0", "pressure": "1009", "temp_C": "2", "temp_F": "36", "visibility": "8", "weatherCode": "116", "weatherDesc": [ {"value": "Mist" } ], "weatherIconUrl": [ {"value": "http:\/\/www.worldweatheronline.com\/images\/wsymbols01_png_64\/wsymbol_0006_mist.png" } ], "winddir16Point": "WNW", "winddirDegree": "290", "windspeedKmph": "7", "windspeedMiles": "4" } ], "request": [ {"query": "Lat 34.47 and Lon -84.42", "type": "LatLon" } ], "weather": [ {"date": "2011-01-06", "precipMM": "9.3", "tempMaxC": "7", "tempMaxF": "45", "tempMinC": "2", "tempMinF": "35", "weatherCode": "113", "weatherDesc": [ {"value": "Sunny" } ], "weatherIconUrl": [ {"value": "http:\/\/www.worldweatheronline.com\/images\/wsymbols01_png_64\/wsymbol_0001_sunny.png" } ], "winddir16Point": "WNW", "winddirDegree": "293", "winddirection": "WNW", "windspeedKmph": "20", "windspeedMiles": "13" }, {"date": "2011-01-07", "precipMM": "0.0", "tempMaxC": "6", "tempMaxF": "44", "tempMinC": "0", "tempMinF": "31", "weatherCode": "116", "weatherDesc": [ {"value": "Partly Cloudy" } ], "weatherIconUrl": [ {"value": "http:\/\/www.worldweatheronline.com\/images\/wsymbols01_png_64\/wsymbol_0002_sunny_intervals.png" } ], "winddir16Point": "WNW", "winddirDegree": "286", "winddirection": "WNW", "windspeedKmph": "25", "windspeedMiles": "16" } ] }}

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  • Emacs with CEDET changes copy/paste to include trailing spaces?

    - by Paul D.
    I just started trying out CEDET today, which I really like, but it seems to do something completely worthless with respect to copying/pasting. If I highlight some stuff and copy it, when it gets pasted back the newlines are eliminated and there is just a ton of trailing whitespace on each line. This is really worthless. All I have in my .emacs right now for CEDET is the following: (load-file "~/.emacs.d/cedet-1.0pre7/common/cedet.el") (require 'semantic-ia) (require 'semantic-gcc) (semantic-load-enable-code-helpers) Does anybody know how to turn this off? I can't find anything about this except that the CEDET main page says it has "magic copy & paste".

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  • How to recover from a fatal error "Allowed memory size exhausted"

    - by Matthieu
    Hi everybody, Do you know any solution to recover from the PHP fatal error : "Allowed memory size ... exhausted" I have a shutdown function that is called when a fatal error appear. This function create an ErrorException from it, and logs it. The problem is : when there is no more memory available, it can't log the error (I log in Firebug, via FirePHP, with Zend Framework). So what i mean by "how to recover from it", is how to perform basic error log, and let Zend Framework send the Headers, so that the error is logged (in Firebug in my case) as any other error ? Thanks

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  • multi-thread access MySQL error

    - by user188916
    I have written a simple multi-threaded C program to access MySQL,it works fine except when i add usleep() or sleep() function in each thread function. i created two pthreads in the main method, int main(){ mysql_library_init(0,NULL,NULL); printf("Hello world!\n"); init_pool(&p,100); pthread_t producer; pthread_t consumer_1; pthread_t consumer_2; pthread_create(&producer,NULL,produce_fun,NULL); pthread_create(&consumer_1,NULL,consume_fun,NULL); pthread_create(&consumer_2,NULL,consume_fun,NULL); mysql_library_end(); } void * produce_fun(void *arg){ pthread_detach(pthread_self()); //procedure while(1){ usleep(500000); printf("producer...\n"); produce(&p,cnt++); } pthread_exit(NULL); } void * consume_fun(void *arg){ pthread_detach(pthread_self()); MYSQL db; MYSQL *ptr_db=mysql_init(&db); mysql_real_connect(); //procedure while(1){ usleep(1000000); printf("consumer..."); int item=consume(&p); addRecord_d(ptr_db,"test",item); } mysql_thread_end(); pthread_exit(NULL); } void addRecord_d(MYSQL *ptr_db,const char *t_name,int item){ char query_buffer[100]; sprintf(query_buffer,"insert into %s values(0,%d)",t_name,item); //pthread_mutex_lock(&db_t_lock); int ret=mysql_query(ptr_db,query_buffer); if(ret){ fprintf(stderr,"%s%s\n","cannot add record to ",t_name); return; } unsigned long long update_id=mysql_insert_id(ptr_db); // pthread_mutex_unlock(&db_t_lock); printf("add record (%llu,%d) ok.",update_id,item); } the program output errors like: [Thread debugging using libthread_db enabled] [New Thread 0xb7ae3b70 (LWP 7712)] Hello world! [New Thread 0xb72d6b70 (LWP 7713)] [New Thread 0xb6ad5b70 (LWP 7714)] [New Thread 0xb62d4b70 (LWP 7715)] [Thread 0xb7ae3b70 (LWP 7712) exited] producer... producer... consumer...consumer...add record (31441,0) ok.add record (31442,1) ok.producer... producer... consumer...consumer...add record (31443,2) ok.add record (31444,3) ok.producer... producer... consumer...consumer...add record (31445,4) ok.add record (31446,5) ok.producer... producer... consumer...consumer...add record (31447,6) ok.add record (31448,7) ok.producer... Error in my_thread_global_end(): 2 threads didn't exit [Thread 0xb72d6b70 (LWP 7713) exited] [Thread 0xb6ad5b70 (LWP 7714) exited] [Thread 0xb62d4b70 (LWP 7715) exited] Program exited normally. and when i add pthread_mutex_lock in function addRecord_d,the error still exists. So what exactly the problem is?

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  • PROC FCMP PROBLEM

    - by Bruno
    I copy the code from a paper that i found on internet. proc fcmp outlib=work.funcs.Test; function whatAmI(); return(42); endsub; quit; options cmplib=work.funcs; data null; rci = whatAmI(); put rci=; /* should be 42 */ run; When I execute the code, it show the message: ERROR 68-185: The function WHATAMI is unknown, or cannot be accessed. I tried other functions and always show this message. I change the libname, but nothing work. What´s wrong?

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  • Error: Get JSON Data from Web API Using Jquery

    - by Kenneth
    I'm really new at this. And I'm really stuck. I have the jquery code, it will load data from Web API, but it does not display on my page. $.getJSON("/api/Order", function(data) { if (data != null) { var str = ''; $.each(data, function (item) { str = '<li>' + item.ItemName + '</li>'; }); $("#contents").append(str); } }); Can anyone explain what is going on? Thanks.

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  • Can you in any way interface Ruby Gems with PHP, Python, etc.?

    - by Chad Johnson
    Stupid question, and forgive me for asking, but someone is asking me, and I am not a super expert with Rails yet. Suppose I have some Rails gem I write. Now suppose a customer has some other framework, like Django or CakePHP, and I want to provide the functionality offered by my gem (eg. CRUD for automotive data) to them as a module in their framework. Could I somehow make it so they could interface my gem with Django or CakePHP? Obviously I could do something with some API magic--and I'll probably end up going that route. But I just want to know whether there is a way to directly interface with Gems from a non-Rails application.

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  • Track only iframe history

    - by evanwong
    I have a page which contains an iframe and I want to track the history of the iframe only. I tried to use the history object like this: <!DOCTYPE html> <html> <head> <title></title> <script type="text/javascript"> function checkFrameHistory() { alert(window.frames["test2"].history.length); } function checkThisHistory() { alert(history.length); } </script> </head> <body> <iframe name="test2" src="test2.html"></iframe> <div> <input type="button" onclick="checkFrameHistory()" value="Frame history"/> <input type="button" onclick="checkThisHistory()" value="This history"/> </div> </body> </html> test2.html <!DOCTYPE html> <html> <head> <title></title> <script type="text/javascript"> function checkMyHistory() { alert(history.length); } </script> </head> <body> <div> Test2 </div> <div> <input type="button" onclick="checkMyHistory()" value="My history"/> </div> </body> </html> but it actually gave me the history including the parent window. For instance, I went to another site in the main window and came back to my iframe test site. Both window.frames["test2"].history.length and history.length still gave me the same count by increasing the length by 2. Did I do it wrong? Is there a way to track only the iframe history?

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