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  • What are the barriers to understanding pointers and what can be done to overcome them?

    - by David McGraw
    Why are pointers such a leading factor of confusion for many new, and even old, college level students in the C/C++ language? Are there any tools or thought processes that helped you understand how pointers work at the variable, function, and beyond level? What are some good practice things that can be done to bring somebody to the level of, "Ah-hah, I got it," without getting them bogged down in the overall concept? Basically, drill like scenarios.

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  • Rails: unexpected behavior updating a shared instance

    - by Pascal Lindelauf
    I have a User object, that is related to a Post object via two different association paths: Post --(has_many)-- comments --(belongs to)-- writer (of type User) Post --(belongs to)-- writer (of type User) Say the following hold: user1.name == "Bill" post1.comments[1].writer == user1 post1.writer == user1 Now when I retrieve the post1 and its comments from the database and I update post1.comments[1].writer like so: post1.comments[1].writer.name = "John" I would expect post1.writer to equal "John" too. But it doesn't! It still equals "Bill". So there seems to be some caching going on, but the kind I would not expect. I would expect Rails to be clever enough to load exactly one instance of the user with name "Bill"; instead is appears to load two individual ones: one for each association path. Can someone explain how this works exactly and how I am to handle these types of situations the "Rails way"?

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  • Rails 2.3: How to create this SQL into a named_scope

    - by randombits
    Having a bit of difficulty figuring out how to create a named_scope from this SQL query: select * from foo where id NOT IN (select foo_id from bar) AND foo.category = ? ORDER BY RAND() LIMIT 1; Category should be variable to change. What's the most efficient way the named_scope can be written for the problem above?

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  • Why is my substitution control suddenly not working in ASP.NET 4.0?

    - by Steve Wortham
    I just upgraded my site from ASP.NET 3.5 to 4.0. I've been working through some breaking changes (there were more than I expected). One I can't figure out, however, is why my <asp:Substitution /> control suddenly stopped working like it should. It's supposed to ignore the output cache settings of the parent page and update upon every request. For some reason that isn't happening. It's caching for the full 10 minutes (the OutputCache setting for my home page). Any ideas?

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  • How do I send information to an HLSL effect in DirectX 10?

    - by pypmannetjies
    I'd like to send my view vector to an ID3D10Effect variable in order to calculate specular lighting. How do I send a vector or even just scalar values to the HLSL from the running DirectX program? I want to do something like render() { //do transformations D3DXMatrix view = camera->getViewMatrix(); basicEffect.setVariable(viewVector, view); //render stuff }

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  • How do I add a filter button to this pagination?

    - by ClarkSKent
    Hey, I want to add a button(link), that when clicked will filter the pagination results. I'm new to php (and programming in general) and would like to add a button like 'Automotive' and when clicked it updates the 2 mysql queries in my pagination script, seen here: As you can see, the category automotive is hardcoded in, I want it to be dynamic, so when a link is clicked it places whatever the id or class is in the category part of the query. 1: $record_count = mysql_num_rows(mysql_query("SELECT * FROM explore WHERE category='automotive'")); 2: $get = mysql_query("SELECT * FROM explore WHERE category='automotive' LIMIT $start, $per_page"); This is the entire current php pagination script that I am using: <?php //connecting to the database $error = "Could not connect to the database"; mysql_connect('localhost','root','root') or die($error); mysql_select_db('ajax_demo') or die($error); //max displayed per page $per_page = 2; //get start variable $start = $_GET['start']; //count records $record_count = mysql_num_rows(mysql_query("SELECT * FROM explore WHERE category='automotive'")); //count max pages $max_pages = $record_count / $per_page; //may come out as decimal if (!$start) $start = 0; //display data $get = mysql_query("SELECT * FROM explore WHERE category='automotive' LIMIT $start, $per_page"); while ($row = mysql_fetch_assoc($get)) { // get data $name = $row['id']; $age = $row['site_name']; echo $name." (".$age.")<br />"; } //setup prev and next variables $prev = $start - $per_page; $next = $start + $per_page; //show prev button if (!($start<=0)) echo "<a href='pagi_test.php?start=$prev'>Prev</a> "; //show page numbers //set variable for first page $i=1; for ($x=0;$x<$record_count;$x=$x+$per_page) { if ($start!=$x) echo " <a href='pagi_test.php?start=$x'>$i</a> "; else echo " <a href='pagi_test.php?start=$x'><b>$i</b></a> "; $i++; } //show next button if (!($start>=$record_count-$per_page)) echo " <a href='pagi_test.php?start=$next'>Next</a>"; ?>

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  • Is there a built-in .NET method for getting all of the properties and values for an object?

    - by Ben McCormack
    Let's say I have: public class Item { public string SKU {get; set; } public string Description {get; set; } } .... Is there a built-in method in .NET that will let me get the properties and values for variable i of type Item that might look like this: {SKU: "123-4556", Description: "Millennial Radio Classic"} I know that .ToString() can be overloaded to provide this functionaility, but I couldn't remember if this was already provided in .NET.

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  • Directory file size calculation - how to make it faster?

    - by Xinxua
    Using C#, I am finding the total size of a directory. The logic is this way : Get the files inside the folder. Sum up the total size. Find if there are sub directories. Then do a recursive search. I tried one another way to do this too : Using FSO (obj.GetFolder(path).Size). There's not much of difference in time in both these approaches. Now the problem is, I have tens of thousands of files in a particular folder and its taking like atleast 2 minute to find the folder size. Also, if I run the program again, it happens very quickly (5 secs). I think the windows is caching the file sizes. Is there any way I can bring down the time taken when I run the program first time??

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  • Android: View.getTag/setTag and IllegalArgumentException

    - by Sparafusile
    Yes, I know you need a unique resource id when calling the version of these functions that requires a key, but I cannot for the life of me figure out how to create a resource id that can be used in this way. A final variable in my class wont work and neither will a hard coded value. Both threw an IllegalArgumentException. So what gives, how do you use these methods? Spara

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  • Convert month number to month short name

    - by Roland
    I have a variable with the following value $month = 201002; the first 4 numbers represent the year, and the last 2 numbers represent the month. I need to get the last 2 numbers in the month string name eg. Feb My code looks like this <?php echo date('M',substr($month,4,6)); ?> I can I go about to obtain the month name

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  • Installing gtk and compiling using gcc under windows?

    - by sil3nt
    I have gcc installed in c:/programfiles (also set as a path variable), and i have all the necessary files for gtk from http://www.gtk.org/download-windows.html, glib,gtk,pango,atk and cairo. Although I have no clue as to how to compile a c program using gtk with the gcc compiler. How do I set everything up so that it works?. (I don't know where each zip file goes.?) basically I don't really know where start.

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  • about null values!

    - by user329820
    Hi I have a question that if we declare a variable and then do not set it explicitly to null value then it would be null outomatically ,i mean that the below code will return true or false ? thanks DECLARE @val CHAR(4) If @val = NULL

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  • Managing a user's PHP session with Cocoa Touch

    - by Calvin L
    I'm building an iPhone app, which will allow users to log in to a PHP web server that authenticates the user and starts a session. My idea for managing a session is to create a singleton User class that has a sharedLogin method. Would it be prudent to store the session variable in the shared instance in order to maintain the session?

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  • Any special assertion to test if the resulting integer lies within a range

    - by barerd
    I would like to test if an instance variable lies in a range of numbers. I solved the problem by using assert_in_delta but would like to know if there is a formal assertion for this. #part of the tested class def initialize(value = 70 + rand(30)) @value = value end #test_value.rb class ValueTestCase < Test::Unit::TestCase def test_if_value_in_range assert_in_delta(85, p.value, 15) end end

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  • set the focus of a popup window everytime

    - by hunt
    I have two pages one.html and two.html i am opening a new window using following code //here popup is a global variable popup=window.open('two.html','two'); for the first time a popup window open successfully and get the focus but if i try to open it again without closing already opened popup then two.html is not getting focus for the second time. note: i have set popup window's name as 'two'

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  • UTF-8 - Oracle issue

    - by goe
    I set my NLS_LANG variable as 'AMERICAN_AMERICA.AL32UTF8' in the perl file that connects to oracle and tries to insert the data. However when I insert a record with one value having this 'ñ' character the sql fails. But if I use 'Ñ' it inserts just fine. What am I doing wrong here?

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  • Mutable global variables don't get hide in python functions, right?

    - by aXqd
    Please see the following code: def good(): foo[0] = 9 # why this foo isn't local variable who hides the global one def bad(): foo = [9, 2, 3] # foo is local, who hides the global one for func in [good, bad]: foo = [1,2,3] print('Before "{}": {}'.format(func.__name__, foo)) func() print('After "{}": {}'.format(func.__name__, foo)) The result is as below: # python3 foo.py Before "good": [1, 2, 3] After "good": [9, 2, 3] Before "bad" : [1, 2, 3] After "bad" : [1, 2, 3]

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  • How to change aif to be able to access 'it' within the macrocall without making 'it' public in the package

    - by Sim
    If you put the aif code presented in onlisp in a package and try to use it in another you run in the problem that packagename:it is not external. (in-package :packagename) (defmacro aif (test-form then-form &optional else-form) ‘(let ((it ,test-form)) (if it ,then-form ,else-form))) wanted call syntax (in-package :otherpackage) (aif (do-stuff) (FORMAT t "~a~%" it) (FORMAT t "just got nil~%")) How can I fix this behavior in code, without making the variable it external in the package declaration and beeing able to access it just by it instead of packagename:it?

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  • How to name variables on the fly in R?

    - by Maiasaura
    Is it possible to create new variable names on the fly? I'd like to read data frames from a list into new variables with numbers at the end. Something like orca1, orca2, orca3... If I try something like paste("orca",i,sep="")=list_name[[i]] I get this error target of assignment expands to non-language object Is there another way around this?

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