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• const return value and template instantiation

  - by Rimo

  From Herb Sutter's GotW #6 Return-by-value should normally be const for non-builtin return types. .... Note: Lakos (pg. 618) argues against returning const value, and notes that it is redundant for builtins anyway (for example, returning "const int"), which he notes may interfere with template instantiation. .... While Sutter seems to disagree on whether to return a const value or non-const value when returning an object of a non-built type by value with Lakos, he generally agrees that returning a const value of a built-in type (e.g const int) is not a good idea. While I understand why that is useless because the return value cannot be modified as it is an rvalue, I cannot find an example of how that might interfere with template instantiation. Please give me an example of how having a const qualifier for a return type might interfere with template instantiation.

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• Tables with no Primary Key

  - by Matt Hamilton

  I have several tables whose only unique data is a uniqueidentifier (a Guid) column. Because guids are non-sequential (and they're client-side generated so I can't use newsequentialid()), I have made a non-primary, non-clustered index on this ID field rather than giving the tables a clustered primary key. I'm wondering what the performance implications are for this approach. I've seen some people suggest that tables should have an auto-incrementing ("identity") int as a clustered primary key even if it doesn't have any meaning, as it means that the database engine itself can use that value to quickly look up a row instead of having to use a bookmark. My database is merge-replicated across a bunch of servers, so I've shied away from identity int columns as they're a bit hairy to get right in replication. What are your thoughts? Should tables have primary keys? Or is it ok to not have any clustered indexes if there are no sensible columns to index that way?

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• Streaming files from EventMachine handler?

  - by Noah

  I am creating a streaming eventmachine server. I'm concerned about avoiding blocking IO or doing anything else to muck up the event loop. From what I've read, ruby's non-blocking IO can be used to stream files in a non-blocking way, or I can call next_tick, but I'm a little unclear about which of these approaches is preferable. Part of the problem is that I have not found a good explanation of non-blocking IO library functions in ruby. Short version: Assuming a long-lived network IO operation, several wall clock minutes of streaming per file, transfer, what is the best way to do this in eventmachine without gumming up the event loop? while 1 do file.read do |bytes| @conn.send_data bytes end end I understand that the above code will block and I'm wondering what to put in its place. Also, I cannot use the FileStreamer class that is part of eventmachine as is, because I need to manipulate the data after it's read but before it's sent. Thanks, Noah

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• php 5.3.2 not throwing exceptions

  - by tipu

  I'm attempting to throw an exception using php 5.3.2 and it is giving me the following error: Parse error: syntax error, unexpected T_THROW I am attempting to throw an exception the following way: throw new Exception('Property ' . $name . ' doesn\'t exist in class Index', ''); Edit: I also tried throw new Exception('Property ' . $name . ' doesn\'t exist in class Index'); it didn't change the error I was getting. The complete method: public function __get($name) { if(property_exists($this, $name) throw new Exception('Property ' . $name . ' doesn\'t exist in class Index'); return $this->$name; }

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• Metatool for automatic xml code generation

  - by iceman

  I want to develop a programming tool for developers which can do automatic xml code generation for specifying a GUI design and its controls. The aim is to allow non-programmers specify GUI controls(which in this case perform higher level task unlike WinForms ) from a GUI. So the xml code generated is essentially an internal representation which programmers can understand and further use in any automatic GUI generator. So the workflow is GUI(non-programmers)-xml(for programmers)-GUI(non-programmers). Is there a Microsoft project similar to this?

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• msvcrt: memory usage goes wild, but not under debugger

  - by al_miro

  I have a C++ code compiled with Intel compiler, 32bit, in MS VC6 mode, so using either msvcrt.dll or msvcrtd.dll. The process makes heavy memory allocation and deallocation. I monitor the memory usage with WMI and look at VirtualSize and WorkingSetSize. with debug runtime (msvcrtd.dll): virtual constant 1.7GB, working constant 1.2GB with non-debug runtime (msvcrt.dll): virtual raising 1.7-- 2.1GB, working raising 1.2-1.4GB with non-debug runtime but under debugger (windbg): virtual constant 1.7GB, working constant At 2.1 GB virtual the process is crashing (as expected). But why would the virtual usage increase only with (non-debug) msvcrt.dll and only if not under debugger? In all cases compilation flags are identical, only runtime libs are different.

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• Excel validation range limits

  - by richardtallent

  When Excel saves a file, it attempts to combine identical Validation settings into a single rule with multiple ranges. This creates one of three issues, depending on the file type you choose to save: When saving as a standard Excel file (Office 2000 BIFF), a maximum of 1024 non-contiguous ranges that can have the same validation setting. When saving as a SpreadsheetML (Office 2002/2003 XML) file, you are limited to the number of non-contiguous ranges that can be represented, comma-delimited in R1C1 format, in 1024 characters. When saving as an Open Office XML (Office 2007 *.xlsx), there is a maximum of 511 non-contiguous ranges that can have the same validation setting. (I don't have Office 2007, I'm using the file converter for Office 2003). Once you bust any of these limits, the remaining ranges with the same Validation settings have their Validation settings wiped. For (1) and (3), Excel warns you that it can't save all of the formatting, but for (2) it does not.

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• WCF hosted in a Web application and compatibility mode

  - by DotnetDude

  I have a WCF service hosted in a web application (IIS). I need to expose 1 end point over wsHttp and the other over netTcp. I am on a IIS7 environment that makes it possible for me to host non HTTP based services. Anyways, when I browse the .svc file using a browser, I get the error: The service cannot be activated because it does not support ASP.NET compatibility. ASP.NET compatibility is enabled for this application By googling, I realized that WCF runs in two modes - Mixed and ASP.NET compatible. When I apply the attribute [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)] However, it appears that once I apply this attribute to the Service Contract implementation, I cannot use a non HTTP binding. How do I set it up so that: I can support non HTTP endpoints I can host the service on a Web app I don't create multiple services one with aspnet compatibility turned on and the other turned off

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• REST API unauthenticated requests exception based on the User-Agent

  - by Shay Tsadok

  Hi All, I am developing a REST API that supports two kinds of authentication protocols: login form authentication - for browser based clients. Simple Basic authentication - for non-browser clients. I developed a flow in which unauthenticated requests redirected to the "login form", the problem is that this is an undesired behavior for non-borwser clients! I thought to solve it by decide according to the "User-Agent" what to do: browsers will be redirected to the "login form" and non-browser clients will get the standard 401:Basic Authentication. A. What do you think about this solution? B. Is there a standard way in Java to check if the request came from browser, or do i need to develop this kind of mechanism by my own? Thanks in advance!

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• Scala and the Java Memory Model

  - by Ben Lings

  The Java Memory Model (since 1.5) treats final fields differently to non-final fields. In particular, provided the this reference doesn't escape during construction, writes to final fields in the constructor are guaranteed to be visible on other threads even if the object is made available to the other thread via a data race. (Writes to non-final fields aren't guaranteed to be visible, so if you improperly publish them, another thread could see them in a partially constructed state.) Is there any documentation on how/if the Scala compiler creates final (rather than non-final) backing fields for classes? I've looked through the language specification and searched the web but can't find any definitive answers. (In comparison the @scala.volatile annotation is documented to mark a field as volatile)

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• How to create a new File in Qt

  - by GG

  Hello friends, I am a Qt beginner and just got stuck with the problem. I am looking for a file SomePath/NewDirectoryA/NewFile.kml ( NewFile.kml will be the only file in NewDirectoryA, having this directory just to maintain semantics in the project ). If SomePath/NewDirectoryA/NewFile.kml exists then I will use it in my code and If it doesn't exist then I have to create it. If this File doesn't exist then this directory also doesn't exist in SomePath. So If only I have to create a file I can use QFile and open it in ReadWrite or WriteOnly mode. But the problem is I have to create the file with the directory itself. I tried with QFile with file name SomePath/NewDirectoryA/NewFile.kml but it didn't worked. Please suggest me a way in which I can create a new file( NewFile.kml ) in a new directory( NewDirectorA ) at a given location( SomePath ).

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• Outlook 2007 addins for filtering attachments accordingly to recipients.

  - by Susanta

  My question is that I need to send attached mail to domain users and non domain users. Domain users will receive .lnk of the attached file where as non domain users will receive physical file. Now I am doing by capturing send event of outlook and internally divided mail in two parts for domain users I crated .lnk of the file and attached it and sent to user. Where as for non domain users i attached the physical file and sent to the user. But these things are done by sending two mails internally so I am not able to maintain CC, BCC information. I need to do these things in one mail. So it is possible in outlook addins to filter attachments accordingly to recipients.

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• Rails best practice on conditional parameters in a controller action

  - by randombits

  I have a controller create action looks for one or more parameters in the following ruleset. Let's say we have two parameters, foo and bar. The rules are the following: 1) if foo doesn't exist in the parameter list, bar must. 2) if bar doesn't exist in the parameter list, foo must. 3) they can both co-exist. they can't both be omitted (that's redundant with my rules above :) ) Can anyone show an example in Rails on how this is handled in the controller? Should I use a before_filter? Would appreciate some guidance as this isn't something that ActiveRecord validates.. so I'd need to build an error message to the user directly from controller logic, not model logic. For bonus points, I output the error in XML, so if you can show how that's done, that'd be great. Hypothetically let's call the resource "Lorem", so it is created via http://foo/lorem.xml and we have lorem_controller.rb.

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• Python os module path functions

  - by broiyan

  From the documentation: os.path.realpath(path) Return the canonical path of the specified filename, eliminating any symbolic links encountered in the path (if they are supported by the operating system). When I invoke this with an extant file's name, I get the path to it: /home/myhome/myproject. When I invoke this with a 'nonsense.xxx' string argument, I still get a path to /home/myhome/myproject/nonsense.xxx. This is a little inconsistent because it looks like nonsense.xxx is taken to be a directory not a file (though it is neither: it does not exist). When I invoke this with a null string file name, I still get a path to /home/myhome/myproject. How can I account for this behaviour when the documentation says so little about realpath()? (I am using Python 2.5.) Edit: Somebody suggested a way to test if files exist. My concern is not to test if files exist. My concern is to account for behaviour.

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• JScript JSON Object Check

  - by George

  I'm trying to check if json[0]['DATA']['name'][0]['DATA']['first_0'] exists or not when in some instances json[0]['DATA']['name'] contains nothing. I can check json[0]['DATA']['name'] using if (json[0]['DATA']['name'] == '') { // DOES NOT EXIST } however if (json[0]['DATA']['name'][0]['DATA']['first_0'] == '' || json[0]['DATA']['name'][0]['DATA']['first_0'] == 'undefined') { // DOES NOT EXIST } returns json[0]['DATA']['name'][0]['DATA'] is null or not an object. I understand this is because the array 'name' doesn't contain anything in this case, but in other cases first_0 does exist and json[0]['DATA']['name'] does return a value. Is there a way that I can check json[0]['DATA']['name'][0]['DATA']['first_0'] directly without having to do the following? if (json[0]['DATA']['name'] == '') { if (json[0]['DATA']['name'][0]['DATA']['first_0'] != 'undefined') { // OBJECT EXISTS } }

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• Oracle Unique Indexes

  - by Melvin

  I was creating a new table today in 10g when I noticed an interesting behavior. Here is an example of what I did: CREATE TABLE test_table ( field_1 INTEGER PRIMARY KEY ); Oracle will by default, create a non-null unique index for the primary key. I double checked this. After a quick check, I find a unique index name SYS_C0065645. Everything is working as expected so far. Now I did this: CREATE TABLE test_table ( field_1 INTEGER, CONSTRAINT pk_test_table PRIMARY KEY (field_1) USING INDEX (CREATE INDEX idx_test_table_00 ON test_table (field_1))); After describing my newly created index idx_test_table_00, I see that it is non-unique. I tried to insert duplicate data into the table and was stopped by the primary key constraint, proving that the functionality has not been affected. It seems strange to me that Oracle would allow a non-unique index to be used for a primary key constraint. Why is this allowed?

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• When does a const return type interfere with template instantiation?

  - by Rimo

  From Herb Sutter's GotW #6 Return-by-value should normally be const for non-builtin return types. ... Note: Lakos (pg. 618) argues against returning const value, and notes that it is redundant for builtins anyway (for example, returning "const int"), which he notes may interfere with template instantiation. While Sutter seems to disagree on whether to return a const value or non-const value when returning an object of a non-built type by value with Lakos, he generally agrees that returning a const value of a built-in type (e.g const int) is not a good idea. While I understand why that is useless because the return value cannot be modified as it is an rvalue, I cannot find an example of how that might interfere with template instantiation. Please give me an example of how having a const qualifier for a return type might interfere with template instantiation.

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• How to define supported BlackBerry OS versions and models for application?

  - by Lyubomyr Dutko

  After company wins a project it is usual to mention in contract what devices are supported and what OS versions are supported. But taking into account BlackBerry it appears sometimes to be tricky, as you can have the same device model, but two and(or) more different OS versions (or within same OS different package versions). And in this situation application may need to be updated. So the main question here is what is expected to be mentioned in contract? Could you please share some your experience of resolving such problems? So as a good example can be case of video playback issue on Storm: some issue exists on 5.0.0.XXX (network provider A) and doesn't exist on 5.0.0.YYY (network provider B), or could be following: 5.0.0.XXX1 (network provider A) - issue exist 5.0.0.XXX2 (network provider A) - issue doesn't exist The point here is to define some boundaries of development company responsibility

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• LINQ to Entity, joining on NOT IN tables

  - by SlackerCoder

  My brain seems to be mush right now! I am using LINQ to Entity, and I need to get some data from one table that does NOT exist in another table. For example: I need the groupID, groupname and groupnumber from TABLE A where they do not exist in TABLE B. The groupID will exist in TABLE B, along with other relevant information. The tables do not have any relationship. In SQL it would be quite simply (there is a more elegant and efficient solution, but I want to paint a picture of what I need) SELECT GroupID, GroupName, GroupNumber, FROM TableA WHERE GroupID NOT IN (SELECT GroupID FROM TableB) Is there an easy/elegant way to do this? Right now I have a bunch of queries hitting the db, then comparing, etc. It's pretty messy. Thanks.

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• How to detect page redirect with PHP?

  - by blabus

  I'm trying to detect whether an image exists on a remote server. However, I've tried several methods and can't get any of them to work. Right now I'm trying to use this: if (!CheckImageExists("http://img2.netcarshow.com/ABT-Audi_R8_2008_1024x768_wallpaper_01.jpg")) { print_r("DOES NOT EXIST"); } else { print_r("DOES EXIST"); }; function CheckImageExists($imgUrl) { if (fopen($imgUrl, "r")) { return true; } else { return false; }; }; But it returns 'true' whether the image actually exists or not (the above image should, but change it to gibberish and it still will return 'true'). I have a feeling it could be because if the URL does not exist, it redirects to the homepage of the site. But I don't know how to detect that. Thanks for any help!

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• Parameter passed by const reference returned by const reference.

  - by Alien01

  Hello, I was reading C++ Faq Second Edition , faq number 32.08 . FAQ says that parameter passed by const reference and returned by const reference can cause dangling reference. But it is ok if parameter is passed by reference and returned by reference. I got it that it is unsafe in case of const reference but how is it safe in case when parameter is non const reference. Last line of FAQ says "Note that if a function accepts a parameter by non-const reference (for example, f(string& s)), returning a copy of this reference parameter is safe because a temporary cannot be passed by non-const reference." Need some insight on this!!

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• Get records based on child condition

  - by Shawn Mclean

  In LINQ To Entities: How do I get the records (including both child and parent) based on a condition of the child in a one to many. My structure is set up as follows: GetResources() - returns a list of Resources. GetResources().ResourceNames - this is the child, which is an entity collection. GetResources().ResourceNames - a property of one record of this child is Name. I'd like to construct something like this: return (from p in repository.GetResources() where p.ResourceNames.Exist(r => r.Name.Contains(text, StringComparison.CurrentCultureIgnoreCase)) select p).ToList(); but of course, Exist doesn't exist. thanks.

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• Python method to remove iterability

  - by Debilski

  Suppose I have a function which can either take an iterable/iterator or a non-iterable as an argument. Iterability is checked with try: iter(arg). Depending whether the input is an iterable or not, the outcome of the method will be different. Not when I want to pass a non-iterable as iterable input, it is easy to do: I’ll just wrap it with a tuple. What do I do when I want to pass an iterable (a string for example) but want the function to take it as if it’s non-iterable? E.g. make that iter(str) fails.

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• Storing apostrophes, exclamation marks, etc. in mysql database

  - by rein

  I changed from latin1 to utf8. Although all sorts of text was displaying fine I noticed non-english characters were stored in the database as weird symbols. I spent a day trying to fix that and finally now non-english characters display as non-english characters in the database and display the same on the browser. However I noticed that I see apostrophes stored as &#39; and exclamation marks stored as &#33;. Is this normal, or should they be appearing as ' and ! in the database instead? If so, what would I need to do in order to fix that?

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• Should every class have its own namespace?

  - by thehouse

  Something that has been troubling me for a while: The current wisdom is that types should be kept in a namespace that only contains functions which are part of the type's non-member interface (see C++ Coding Standards Sutter and Alexandrescu or here) to prevent ADL pulling in unrelated definitions. Does this imply that all classes must have a namespace of their own? If we assume that a class may be augmented in the future by the addition of non-member functions, then it can never be safe to put two types in the same namespace as either one of them may introduce non-member functions that could interfere with the other. The reason I ask is that namespaces are becoming cumbersome for me. I'm writing a header-only library and I find myself using classes names such as project::component::class_name::class_name. Their implementations call helper functions but as these can't be in the same namespace they also have to be fully qualified!

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