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• consts and other animals

  - by bks

  Hello i have a cpp code wich i'm having trouble reading. a class B is defined now, i understand the first two lines, but the rest isn't clear enough. is the line "B const * pa2 = pa1" defines a const variable of type class B? if so, what does the next line do? B a2(2); B *pa1 = new B(a2); B const * pa2 = pa1; B const * const pa3 = pa2; also, i'm having trouble figuring out the difference between these two: char const *cst = “abc”; const int ci = 15; thank you

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• Why is this postgresql query so slow?

  - by user315975

  I'm no database expert, but I have enough knowledge to get myself into trouble, as is the case here. This query SELECT DISTINCT p.* FROM points p, areas a, contacts c WHERE ( p.latitude > 43.6511659465 AND p.latitude < 43.6711659465 AND p.longitude > -79.4677941889 AND p.longitude < -79.4477941889) AND p.resource_type = 'Contact' AND c.user_id = 6 is extremely slow. The points table has fewer than 2000 records, but it takes about 8 seconds to execute. There are indexes on the latitude and longitude columns. Removing the clause concering the resource_type and user_id make no difference. The latitude and longitude fields are both formatted as number(15,10) -- I need the precision for some calculations. There are many, many other queries in this project where points are compared, but no execution time problems. What's going on?

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• How can I reverse ruby's include function.

  - by Glen

  I'll explain what i'm looking for in code as thats probably the most succinct: module Mixin def method puts "Foo" end end class Whatever include Mixin end w = Whatever.new w.method => "Foo" # some magic here w2 = Whatever.new w.method => NoMethodError I had tried just undefining the Mixin module using remove_const, but this doesn't seem to make any difference to Whatever. I had assumed that #include just added a reference to the module into the class's method resolution chain - but this behaviour doesn't agree with that. Can anyone tell me what include actually does behind the scenes, and how to reverse this?

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• MySQL inner join different results

  - by Darryl at NetHosted

  I am trying to work out why the following two queries return different results: SELECT DISTINCT i.id, i.date FROM `tblinvoices` i INNER JOIN `tblinvoiceitems` it ON it.userid=i.userid INNER JOIN `tblcustomfieldsvalues` cf ON it.relid=cf.relid WHERE i.`tax` = 0 AND i.`date` BETWEEN '2012-07-01' AND '2012-09-31' and SELECT DISTINCT i.id, i.date FROM `tblinvoices` i WHERE i.`tax` = 0 AND i.`date` BETWEEN '2012-07-01' AND '2012-09-31' Obviously the difference is the inner join here, but I don't understand why the one with the inner join is returning less results than the one without it, I would have thought since I didn't do any cross table references they should return the same results. The final query I am working towards is SELECT DISTINCT i.id, i.date FROM `tblinvoices` i INNER JOIN `tblinvoiceitems` it ON it.userid=i.userid INNER JOIN `tblcustomfieldsvalues` cf ON it.relid=cf.relid WHERE cf.`fieldid` =5 AND cf.`value` REGEXP '[A-Za-z]' AND i.`tax` = 0 AND i.`date` BETWEEN '2012-07-01' AND '2012-09-31' But because of the different results that seem incorrect when I add the inner join (it removes some results that should be valid) it's not working at present, thanks.

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• Is it faster to loop through a Python set of number or a set of letters?

  - by Scott Bartell

  Is it faster to loop through a Python set of numbers or a Python set of letters given that each set is the exact same length and each item within each set is the same length? Why? I would think that there would be a difference because letters have more possible characters [a-zA-Z] than numbers [0-9] and therefor would be more 'random' and likely affect the hashing to some extent. numbers = set([00000,00001,00002,00003,00004,00005, ... 99999]) letters = set(['aaaaa','aaaab','aaaac','aaaad', ... 'aaabZZ']) # this is just an example, it does not actually end here for item in numbers: do_something() for item in letters: do_something() where len(numbers) == len(letters) Update: I am interested in Python's specific hashing algorithm and what happens behind the scenes with this implementation.

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• How do I implement this public accesible enum

  - by Psytronic

  Hey guys, I'm trying to access my class's private enum. But I don't understand the difference needed to get it working compared to other members; If this works: private double dblDbl = 2; //misc code public double getDblDbl{ get{ return dblDbl; } } Why can I not do it with enum? private enum myEnum{ Alpha, Beta}; //misc code public Enum getMyEnum{ get{ return myEnum; } } //throws "Window1.myEnum" is a "type" but is used like a variable

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• In .net, how do I choose between a Decimal and a Double

  - by Ian Ringrose

  We were discussing this the other day at work and I wish there was a Stackoverflow question I would point people at so here goes.) What is the difference between a Double and a Decimal? When (in what cases) should you always use a Double? When (in what cases) should you always use a Decimal? What’s the diver factors to consider in cases that don’t fall into one of the two camps above? (There a lot of questions that overlap this question, but they tend to be asking what someone should do in a given case, not how to decide in the general case)

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• Why do my WPF UIElements NOT have OnPreview events?

  - by Matt.M

  I'm building a custom Silverlight UserControl which needs to listen to events using Preview/Tunneling, but for some reason the compiler is telling me they are not recognized or accessible. For example, I can add an event handler to MouseLeftButtonDown, but not PreviewMouseLeftButtonDown. This doesn't make sense because according to Microsoft (http://msdn.microsoft.com/en-us/library/system.windows.uielement_members(v=VS.100).aspx) all UIElements should have Preview events attached. Any ideas as to why this is happening? I'm using Visual Studio 2010 Trial, Blend 4 RC and .Net 4, if that makes a difference.

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• Foreign key on table A --> B, AND foreign key on table B --> A. How is this done?

  - by unclaimedbaggage

  Hi, I have two tables - 'business' and 'business_contacts'. The business_contact table has a many-to-one relationship with the business table. Furthermore, each business has a 'primary contact' field - which I'd assume is a one-to-many relationship with the business_contacts table. The problem, of course, is that this creates a catch-22 for data insertion. Since neither field can be null, I can't insert a business_contact until I have a corresponding business, but I can't insert a business until I have a corresponding business_contact. If anyone could help me get my head around how mutual one-to-many relationships are supposed to be dealt with I'd be most appreciative. (Project being done in MySQL if it makes any difference)

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• URIs vs Hidden Forms

  - by NateDogg

  I'm working in the Codeigniter framework, and want to send requests to my controller/model that have several variables involved. Is there a difference between passing those variables via a hidden form (i.e. using "post") as opposed to passing them through URIs (e.g. 'travel/$month/$day/')? What about security concerns? e.g. URIs: http://www.example.com/travel/$month/$day/ Hidden Form: form_hidden('month',$month); form_hidden('day',$day);

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• rails controller defaults to respond with application/xml in production

  - by Dave Paroulek

  I have a standard contacts_controller.rb with index action that responds as follows: respond_to do |format| format.html format.xml { render :xml => @contacts } end In development, it works as intended: when I browse to http://localhost:3000/contacts, I get an html response. But, when I start the app using capistrano on a remote Ubuntu server and browse to the same url, I get an xml response. If I go to http://remote_host:8000/contacts.html, then I see the html response. If I comment out the format.xml { render :xml => @contacts }, then I see the desired html response. Pretty sure I'm missing something subtle about difference between Rails development and production modes. Any ideas about what I'm overlooking? Thanks, - Dave

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• function to efficiently check a change of value in a nested hashmap

  - by zcaudate

  the motivation is for checking what has changed in a deeply nest map, kind of like a reverse of update-in. This is a simple example: (def p1 {:a {:a1 :1 :a2 :2} :b {:b1 :1 :b2 :2}}) (def p2 (update-in p1 [:a :a1] (constantly :updated)) ;; => {:a {:a1 :updated :a2 :2} ;; :b {:b1 :1 :b2 :2}} (what-changed? p1 p2) ;; => {:keys [:a :a1] :value :updated) (what-changed? p2 p1) ;; => {:keys [:a :a1] :value :2) I'm hoping that because clojure maps are persistent data-structures, there may be a smart algorithm to figure this out by looking at the underlying structure as opposed to walking through the nested maps and comparing the difference.

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• Objective-c pointer assignment and reassignment dilema

  - by moshe

  Hi, If I do this: 1 NSMutableArray *near = [[NSMutableArray alloc] init]; 2 NSMutableArray *all = [[NSMutableArray alloc] init]; 3 NSMutableArray *current = near; 4 current = all; What happens to near? At line 3, am I setting current to point to the same address as near so that I now have two variables pointing to the same place in memory, or am I setting current to point to the location of near in memory such that I now have this structure: current - near - NSMutableArray The obvious difference would be the value of near at line 4. If the former is happening, near is untouched and still points to its initial place in memory. If the latter is happening,

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• Magento data-install script

  - by Vladimir Kerkhoff

  I'm trying to build a data install script that I use to setup a new webstore. This script creates the categories, pages and static blocks and default settings for the specific shop (we use a multistore setup to host the shops). In our dev/staging setup this scripts runs great and all categories are build without any problem. But on our live system this script fails. After some debugging I found the difference is in the Flat catalog usage on the live systems. The problem with creating the category with the flat tables enabled is in getting the parent path information based on the parentId given: $parentCategory = Mage::getModel('catalog/category')->load($parentId); Without flat categories enabled this gives a correct parentCategory, but with flat categories enabled it gives an empty object. Why is this behaviour with flat categories enabled?

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• The meaning of tracking in git

  - by user273158

  In an article that has been cited in StackOverflow a few times (e.g. 1) , the author discusses the asymmetry between git push and git pull, and mentions the following: Update: Thanks to David Ongaro, who points out below that since git 1.7.4.2, the recommended value for the push.default option is upstream rather than tracking, although tracking can still be used as a deprecated synonym. The commit message that describes that change is nice, since it suggests that there is an effort underway to deprecate the term “track” in the context of setting this association with the upstream branch in a remote repository. (The totally different meanings of “track” in git branch --track and “remote-tracking branches” has long irritated me when trying to introduce git to people.) What is exactly the difference that he is referring to with: The notion of "tracking" in git branch --track The notion of "tracking" in remote-tracking branches in the last sentence?

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• mod_rewrite to change my urls

  - by user319859

  Hi, I've been fighting with mod-rewrite for a while. Basically, I have a website that I'm moving to a difference namespace/directory. What I'd like to do is change urls that look like this: http://mydomain.com/index.php?a=xxxxxxxxxx These urls will always have "index.php?a=". I have a different/new site that also has an index.php file, so it's important that I do a rewrite only when a= is in the URL. The new url should be like http://mydomain.com/ns1/index.php?a=xxxxxxxxxxx Seems pretty simple, but i can't seem to get mod_rewrite to do it for me, here's what I have: # rewrite old urls to new namespace RewriteRule ^/index.php\?a=(.*)$ /gc1/index.php\?x=1&a=$1 [R=301,L] See anything wrong?

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• Facebook access token: server-side vs client-side flows

  - by alexey

  Facebook docs: Facebook Platform supports two different OAuth 2.0 flows for user login: server-side (known as the authentication code flow in the specification) and client-side (known as the implicit flow). The server-side flow is used whenever you need to call the Graph API from your web server. The client-side flow is used when you need to make calls to the Graph API from a client, such as JavaScript running in a Web browser or from a native mobile or desktop app. What is the difference between access tokens taken by these flows? It seems like they length differ. Can we use server-side flow token on a client? And otherwise, can we use client-side flow token on a server?

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• Access 2007: Dynamic SQL to be run when opening a report

  - by blockcipher

  I'm trying to have some SQL execute when I open a report. This works fine when I try to match on a column that's an integer with an integer, but when I try to match on a "text" column, it keeps popping up a dialog asking for what you want to filter on. Here's a somple query: select person_phone_numbers.person_id from person_phone_numbers where phone_number = '444-444-4444' This is actually a sub-query I'm trying to use, but this is where the problem is. If I change it to this it works fine: select person_phone_numbers.person_id from person_phone_numbers where phone_id = 2 I put this in the OnOpen event and I'm assigning it to Me.RecordSource if that makes a difference. My goal here is to have a form accept query parameter(s) and have it open a report with the results. Any thoughts on why it wants to ask for a parameter vs. just running the query the way I have it?

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• Making uppercase of std::string

  - by Daniel K.

  Which implementation do you think is better? std::string ToUpper( const std::string& source ) { std::string result; result.reserve( source.length() ); std::transform( source.begin(), source.end(), result.begin(), std::ptr_fun<int, int>( std::toupper ) ); return result; } and... std::string ToUpper( const std::string& source ) { std::string result( source.length(), '\0' ); std::transform( source.begin(), source.end(), result.begin(), std::ptr_fun<int, int>( std::toupper ) ); return result; } Difference is that the first one uses reserve method after the default constructor, but the second one uses the constructor accepting the number of characters.

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• Which libraries use the "We Know Where You Live" optimization for std::make_shared?

  - by KnowItAllWannabe

  Over two years ago, Stephan T. Lavavej described a space-saving optimization he implemented in Microsoft's implementation of std::make_shared, and I know from speaking with him that Microsoft has nothing against other library implementations adopting this optimization. If you know for sure whether other libraries (e.g., for Gnu C++, Clang, Intel C++, plus Boost (for boost::make_shared)) have adopted this implementation, please contribute an answer. I don't have ready access to that many make_shared implementations, nor am I wild about digging into the bowels of the ones I have to see if they've implemented the WKWYL optimization, but I'm hoping that SO readers know the answers for some libraries off-hand. I know from looking at the code that as of Boost 1.52, the WKWYL optimization had not been implemented, but Boost is now up to version 1.55. Note that this optimization is different from std::make_shared's ability to avoid a dedicated heap allocation for the reference count used by std::shared_ptr. For a discussion of the difference between WKWYL and that optimication, consult this question.

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• FtpWebResponse and StreamReader - specifying an offset

  - by AJ

  Hi, I am using the FtpWebRequest / FtpWebResponse objects in C# to download files from a server - so far, so good. I create a StreamReader object from the response stream and use a StreamWriter to create a local file. Now, the file I am reading happens to be in a very simple 'archive' format - there is a small TOC at the start of the file followed by the actual file data. I can therefore read the TOC and get a file offset and size of the data I want to download. My question is: Supposing the offset is 1024. I would use StreamReader.Read(buffer, 1024, length), but will .NET and the FTP protocol actually allow me to skip bytes 0-1023, or does the reader still go through the (relatively) slow process of downloading and discarding the bytes I don't need? This may make the difference between whether I want to use a single archive file, or a TOC file with the data files stored separately. As a bit of a secondary question, would my mileage vary using the Http classes instead of Ftp? Cheers, Adam

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• jQuery UI Slider Problem

  - by OneNerd

  I have been using jQuery sliders for about a week now without issues in my project, but I just hit an issue. I am adding 3 sliders to my page All 3 are added exact same way (like this): $('#slider_id').slider({value:100,'slide':function(e, ui){// some code}}); 2 work properly One does not work (it gives me a fiebug error 'f is undefined') when I drag the slider handle The only glaring difference I can see is that the one giving the error is inside of a jQuery UI dialog(). Interestingly, when I place it outside of the dialog, it works! So, wondering if there are known issues with sliders inside dialogs, and/or if there are any workarounds. Thanks

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• what \bin to add to system Path env var from a jdk

  - by raticulin

  If you install the latest java 1.6 jdk, without installing the public jre option, you end up having two \bin dirs with java.exe: %JAVA_HOME%\jre\bin %JAVA_HOME%\bin if you compare those dirs, there are a few files that are identical (java.exe etc), and a bunch that are either in one or the other. So far I used to add %JAVA_HOME%\bin to my Path environment var, but now I am wondering, does it make a difference? Is there any side effect to choose one or the other? And would not be much cleaner if the installation had only one java.exe and \bin folder?

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• Appending html code to a section inside a dialog window isn't working in IE6

  - by user338413

  I'm using jQuery's validation on a form. When the form is validated, I'm using a submitHandler to fill a dialog with data from the form then I open the dialog to display it. Works great except for in IE6. Nothing displays. I've tried initializing the dialog before and after running the validation code but neither makes a difference. Here's the validation code: $("#acct").validate({ ... submitHandler: function() { fillVerificationDialog(); $("#verification_dialog").dialog('open'); return false; } }); Here's the fillVerificationDialog: function fillVerificationDialog() { $("#dialog-data").empty(); $("<span class='label'>").text("First Name: ").appendTo("#dialog-data"); $("<span class='value'>").text($("#firstname").val()).appendTo("#dialog-data"); $("<br/>").appendTo("#dialog-data"); ... }

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• Would using a MemoryMappedFile for IPC across AppDomains be faster than WCF/named pipes?

  - by Morten Mertner

  Context: I am loading and executing untrusted code in a separate AppDomain and am currently communicating between the two using WCF (using named pipes as the underlying transport). I am exchanging relatively simple object graphs using a reasonably coarse-grained API, but would like to use a more fine-grained API if it does not cost me performance-wise. I've noticed that 4.0 adds a MemoryMappedFile class (which doesn't need a physical file, so could be entirely memory based). What kind of performance gains could I expect to see (if any) by using this new class? I know that it would take some "infrastructure code" to get the request/response behavior of WCF, but for now I'm only interested in the performance difference.

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