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  • What is the rationale to non allow overloading of C++ conversions operator with non-member functio

    - by Vicente Botet Escriba
    C++0x has added explicit conversion operators, but they must always be defined as members of the Source class. The same applies to the assignment operator, it must be defined on the Target class. When the Source and Target classes of the needed conversion are independent of each other, neither the Source can define a conversion operator, neither the Target can define a constructor from a Source. Usually we get it by defining a specific function such as Target ConvertToTarget(Source& v); If C++0x allowed to overload conversion operator by non member functions we could for example define the conversion implicitly or explicitly between unrelated types. template < typename To, typename From operator To(const From& val); For example we could specialize the conversion from chrono::time_point to posix_time::ptime as follows template < class Clock, class Duration operator boost::posix_time::ptime( const boost::chrono::time_point& from) { using namespace boost; typedef chrono::time_point time_point_t; typedef chrono::nanoseconds duration_t; typedef duration_t::rep rep_t; rep_t d = chrono::duration_cast( from.time_since_epoch()).count(); rep_t sec = d/1000000000; rep_t nsec = d%1000000000; return posix_time::from_time_t(0)+ posix_time::seconds(static_cast(sec))+ posix_time::nanoseconds(nsec); } And use the conversion as any other conversion. So the question is: What is the rationale to non allow overloading of C++ conversions operator with non-member functions?

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  • Boost::Mutex & Malloc

    - by M. Tibbits
    Hi all, I'm trying to use a faster memory allocator in C++. I can't use Hoard due to licensing / cost. I was using NEDMalloc in a single threaded setting and got excellent performance, but I'm wondering if I should switch to something else -- as I understand things, NEDMalloc is just a replacement for C-based malloc() & free(), not the C++-based new & delete operators (which I use extensively). The problem is that I now need to be thread-safe, so I'm trying to malloc an object which is reference counted (to prevent excess copying), but which also contains a mutex pointer. That way, if you're about to delete the last copy, you first need to lock the pointer, then free the object, and lastly unlock & free the mutex. However, using malloc to create a boost::mutex appears impossible because I can't initialize the private object as calling the constructor directly ist verboten. So I'm left with this odd situation, where I'm using new to allocate the lock and nedmalloc to allocate everything else. But when I allocate a large amount of memory, I run into allocation errors (which disappear when I switch to malloc instead of nedmalloc ~ but the performance is terrible). My guess is that this is due to fragmentation in the memory and an inability of nedmalloc and new to place nice side by side. There has to be a better solution. What would you suggest?

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  • How to extract Twitter username from Search API via PHP

    - by Alexia
    The Twitter Search api returns results in ATOM/XML format which look like this: <author> <name>username (Friendly Name)</name> <uri>http://twitter.com/username</uri> </author> In my PHP I can get the name field as a variable, so it would look like this: $names = "username (Friendly Name)" But I want to use PHP to extract them as seperate variables, like this: $username = "username" $friendlyName = "Friendly Name" (without parantheses) TIA!

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  • Declaring an array of linked list in C#

    - by xarzu
    I got the compile error message "Array size cannot be specified in a variable declaration (try initializing with a 'new' expression)" when I tried to declare an array of linked lists. public LinkedList[2] ExistingXMLList; Also, if I wanted to create a small array of strings, isn't this the way: string [2] inputdata;

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  • Corner Cases, Unexpected and Unusual Matlab

    - by Mikhail
    Over the years, reading others code, I encountered and collected some examples of Matlab syntax which can be at first unusual and counterintuitive. Please, feel free to comment or complement this list. I verified it r2006a. set([], 'Background:Color','red') Matlab is very forgiving sometimes. In this case, setting properties to an array of objects works also with nonsense properties, at least when the array is empty. myArray([1,round(end/2)]) This use of end keyword may seem unclean but is sometimes very handy instead of using length(myArray). any([]) ~= all([]) Surprisigly any([]) returns false and all([]) returns true. And I always thought that all is stronger then any. EDIT: with not empty argument all() returns true for a subset of values for which any() returns true (e.g. truth table). This means that any() false implies all() false. This simple rule is being violated by Matlab with [] as argument. Loren also blogged about it. Select(Range(ExcelComObj)) Procedural style COM object method dispatch. Do not wonder that exist('Select') returns zero! [myString, myCell] Matlab makes in this case an implicit cast of string variable myString to cell type {myString}. It works, also if I would not expect it to do so. [double(1.8), uint8(123)] => 2 123 Another cast example. Everybody would probably expect uint8 value being cast to double but Mathworks have another opinion. a = 5; b = a(); It looks silly but you can call a variable with round brackets. Actually it makes sense because this way you can execute a function given its handle. a = {'aa', 'bb' 'cc', 'dd'}; Surprsisingly this code neither returns a vector nor rises an error but defins matrix, using just code layout. It is probably a relict from ancient times. set(hobj, {'BackgroundColor','ForegroundColor'},{'red','blue'}) This code does what you probably expect it to do. That function set accepts a struct as its second argument is a known fact and makes sense, and this sintax is just a cell2struct away. Equvalence rules are sometimes unexpected at first. For example 'A'==65 returns true (although for C-experts it is self-evident). About which further unexpected/unusual Matlab features are you aware?

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  • What operation type invoked a trigger in SQL Server 2008?

    - by Neil Moss
    I'm contemplating a single SQL trigger to handle INSERT, UPDATE and DELETE operations as part of an auditing process. Is there any statement, function or @@ variable I can interrogate to find out which operation type launched the trigger? I've seen the following pattern: declare @type char(1) if exists (select * from inserted) if exists (select * from deleted) select @Type = 'U' else select @Type = 'I' else select @Type = 'D' but is there anything else a little more direct or explicit? Thanks, Neil.

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  • Make HTML content area fit to viewport height?

    - by viatropos
    I just made this demo extracting out what I'm trying to accomplish: Autosize Main Content Area I want the pink/yellow area to act according to these rules: Minimum height is the size of its content (which is variable) IF content size is smaller than viewport size Otherwise minimum height is such that it adjusts to fill the window. Checking out the source to that demo, what am I missing? I feel like this is a pretty easy case that shouldn't require javascript. Any ideas?

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  • PHP regex extract date

    - by apis17
    i have $date variable 2009-04-29 which is Y-m-d anybody can give idea how to extract into $d, $m, $y using simplest method as possible? regex is preferable. any more suggestion with simple method will be chosen. :)

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  • What is a python equivalent of PHP's var_dump()

    - by Zoredache
    When debugging in PHP I frequently find it useful to simply stick a var_dump($foo, $bar, ...) in my code to show me the the what a variable is, what is value is, and the same for anything that it contains. What is a good python equivalent for this? I have seen several things in my Google searching that are somewhat equivalent, but nothing that is the same or better.

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  • Enum values doubts?

    - by maddy
    Hi all, Is there any possible way to do any arithmetic operations on enum values enum Type{Zero=0,One,Two,Three,Four,Five,Six,Seven,Eight,Nine}; main() { enum Type Var = Zero; for(int i=0;i<10;i++) { switch(Var) { case Zero: /*do something*/ case One: /*Do something*/ ..... } Var++;(I know that this increment is not possible,But is there anyway by which we can have this variable named Var increment. regards maddy

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  • Error processing Spree sample images - file not recognized by identify command in paperclip geometry.rb:29

    - by purpletonic
    I'm getting an error when I run the Spree sample data. It occurs when Spree tries to load in the product data, specifically the product images. Here's the error I'm getting: * Execute db:load_file loading ruby <GEM DIR>/sample/lib/tasks/../../db/sample/spree/products.rb -- Processing image: ror_tote.jpeg rake aborted! /var/folders/91/63kgbtds2czgp0skw3f8190r0000gn/T/ror_tote.jpeg20121007-21549-2rktq1 is not recognized by the 'identify' command. <GEM DIR>/paperclip-2.7.1/lib/paperclip/geometry.rb:31:in `from_file' <GEM DIR>/spree/core/app/models/spree/image.rb:35:in `find_dimensions' I've made sure ImageMagick is installed correctly, as previously I was having problems with it. Here's the output I'm getting when running the identify command directly. $ identify Version: ImageMagick 6.7.7-6 2012-10-06 Q16 http://www.imagemagick.org Copyright: Copyright (C) 1999-2012 ImageMagick Studio LLC Features: OpenCL ... other usage info omitted ... I also used pry with the pry-debugger and put a breakpoint in geometry.rb inside of Paperclip. Here's what that section of geometry.rb looks like: # Uses ImageMagick to determing the dimensions of a file, passed in as either a # File or path. # NOTE: (race cond) Do not reassign the 'file' variable inside this method as it is likely to be # a Tempfile object, which would be eligible for file deletion when no longer referenced. def self.from_file file file_path = file.respond_to?(:path) ? file.path : file raise(Errors::NotIdentifiedByImageMagickError.new("Cannot find the geometry of a file with a blank name")) if file_path.blank? geometry = begin silence_stream(STDERR) do binding.pry Paperclip.run("identify", "-format %wx%h :file", :file => "#{file_path}[0]") end rescue Cocaine::ExitStatusError "" rescue Cocaine::CommandNotFoundError => e raise Errors::CommandNotFoundError.new("Could not run the `identify` command. Please install ImageMagick.") end parse(geometry) || raise(Errors::NotIdentifiedByImageMagickError.new("#{file_path} is not recognized by the 'identify' command.")) end At the point of my binding.pry statement, the file_path variable is set to the following: file_path => "/var/folders/91/63kgbtds2czgp0skw3f8190r0000gn/T/ror_tote.jpeg20121007-22732-1ctl1g1" I've also double checked that this exists, by opening my finder in this directory, and opened it with preview app; and also that the program can run identify by running %x{identify} in pry, and I receive the same version Version: ImageMagick 6.7.7-6 2012-10-06 Q16 as before. Removing the additional digits (is this a timestamp?) after the file extension and running the Paperclip.run command manually in Pry gives me a different error: Cocaine::ExitStatusError: Command 'identify -format %wx%h :file' returned 1. Expected 0 I've also tried manually updating the Paperclip gem in Spree to 3.0.2 and still get the same error. So, I'm not really sure what else to try. Is there still something incorrect with my ImageMagick setup?

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  • Getting HTTP GET variables using Tipfy

    - by Vestonian
    Hey everyone, I'm currently playing around with tipfy on Google's Appengine and just recently ran into a problem: I can't for the life of me find any documentation on how to use GET variables in my application, I've tried sifting through both tipfy and Werkzeug's documentations with no success. I know that I can use request.form.get('variable') to get POST variables and **kwargs in my handlers for URL variables, but that's as much as the documentation will tell me. Any ideas?

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  • log4j properties file: how to configure ?

    - by EugeneP
    Is it right that the procedure of using log4j looks like this: 1) put a .properties file somewhere in a project folder 2) in an initialization method, that runs only once, invoke PropertyConfigurator.configure("path_to_file"); 3) in every method we need to use logger we define a static logger variable and simply invoke getLogger(class) I'm asking you this: what if the initialization module is not defined? Where to put "log4j.properties" file so that we wouldn't need to invoke propertyconfigurator.configure at all, or if it's not possible, is it ok to invoke PropertyConfigurator.configure("path_to_file") in every method that uses a logger?

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  • How to find State location from iphone GPS?

    - by Silent
    Hello all I'm trying to add to my program that locates the person in GPS but sets a value to the State that person is in so example: GPS Locates person from his/her iphone then returns the state they are in so say its California then the state variable gets set to California as a string would someone have an example any help is appreciated thanks!

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  • XPath find element based on ancestor element

    - by martymcfly
    Hi, again I have Java AST which is created from public class Test { String o = new String("hh"); public void wrong1() { synchronized(o) { // huhu } } } I try to create a XPath query which finds the synchronized block in which the defined String variable o is used. As the definition is above it is an ancestor of the SynchronizedStatement, but I dont get it working //SynchronizedStatement[Expression/PrimaryExpression/PrimaryPrefix/Name[@Image=ancestor::ClassOrInterfaceBody[ClassOrInterfaceBodyDeclaration/FieldVariableDeclaratorId/@Image]]] I know that /SynchronizedStatement[Expression/PrimaryExpression/PrimaryPrefix/Name[@Image= is correct, my problem is how to address the ancestor ClassOrInterfaceBody part. Hope its clear what i mean ;-) Thanks

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  • Copy object values in Visual Studio debug mode

    - by Farinha
    In Visual Studio debug mode it's possible to hover over variables to show their value and then right-click to "Copy", "Copy Expression" or "Copy Value". In case the variable is an object and not just a basic type, there's a + sign to expand and explore the object. It there a way to copy all that into the clipboard?

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