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  • Why Constant Keyword is not introduced In Java?

    - by harigm
    I am curious learner of Java, I was thinking on one topic "CONSTANTS" I have learnt that Java allows us to declare constants by using "Final" keyword. My question is Java didnot introduce Constant(Const) Keyword. Since many people say it has come from C++, in C++ we have Const keyword Is there any strong reason behind, Please share your thoughts on this.

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  • Why is there no Constant keyword in Java?

    - by harigm
    I am curious learner of Java, and I was thinking about the topic of "CONSTANTS". I have learnt that Java allows us to declare constants by using final keyword. My question is why didn't Java introduce Constant (const) keyword. Since many people say it has come from C++, in C++ we have const keyword. Please share your thoughts.

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  • RAILS_ROOT require?

    - by mportiz08
    I'm trying to access the RAILS_ROOT constant in a file residing in the /lib directory, but I'm not able to (uninitialized constant error). Is there something that I need to require to be able to do this? Sorry if this is a dumb question..

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  • Rails route error? uninitialized constant ActiveResource::Base

    - by Marco
    I'm following the Getting Started with Rails guide but ran into an issue opening http://localhost:3000 Shell output: [2010-03-23 19:19:14] ERROR NameError: uninitialized constant ActiveResource::Base Error in the browser: Internal Server Error uninitialized constant ActiveResource::Base WEBrick/1.3.1 (Ruby/1.8.7/2009-06-12) at localhost:3000 I followed the directions exactly as they were specified in the guide: Ran rails generate controller home index I removed index.html Added root :to = "home#index" to config/routes.rb I checked app/views/home/index.html.erb and it is indeed there. I then used rails server to launch the server. At first attempt the browser loads a blank page, but afterwards starts showing the browser error above. Why is it that Rails can't locate the index.html.erb file? Or is the error something different? - Running Rails 3.0beta with Ruby 1.8.7

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  • Allocate constant memory

    - by Vlad
    I'm trying to set my simulation params in constant memory but without luck (CUDA.NET). cudaMemcpyToSymbol function returns cudaErrorInvalidSymbol. The first parameter in cudaMemcpyToSymbol is string... Is it symbol name? actualy I don't understand how it could be resolved. Any help appreciated. //init, load .cubin float[] arr = new float[1]; arr[0] = 0.0f; int size = Marshal.SizeOf(arr[0]) * arr.Length; IntPtr ptr = Marshal.AllocHGlobal(size); Marshal.Copy(arr, 0, ptr, arr.Length); var error = CUDARuntime.cudaMemcpyToSymbol("param", ptr, 4, 0, cudaMemcpyKind.cudaMemcpyHostToDevice); my .cu file contain __constant__ float param;

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  • C# Changing a constant

    - by Jane T
    I have inherited a small windows form based program written in C# that uses a 'constant' (See below), I need to modify this program so 'PROPERTY_NAME' can be "jobs" and "careers". private const string PROPERTY_NAME = "jobs"; I'm guessing a constant isn't designed to change so should I need to change this. The line above is set once at the top of a class file and then PROPERTY_NAME is used throughout that file. On the main form I would like to add two radio buttons 1 called 'jobs' and one called 'careers' and then change the PROPERTY_NAME in the class file based on which is selected. Would I need to pass the radio button status to the method in the class file? I recall reading that I can't simply read the radio button value from the class file. Many thanks for your advice. Jane

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  • Where to put constant strings in C++: static class members or anonymous namespaces

    - by stone
    I need to define some constant strings that will be used only by one class. It looks like I have three options: Embed the strings directly into locations where they are used. Define them as private static constant members of the class: //A.h class A { private: static const std::string f1; static const std::string f2; static const std::string f3; }; //A.cpp const std::string f1 = "filename1"; const std::string f2 = "filename2"; const std::string f3 = "filename3"; //strings are used in this file Define them in an anonymous namespace in the cpp file: //A.cpp namespace { const std::string f1 = "filename1"; const std::string f2 = "filename2"; const std::string f3 = "filename3"; } //strings are used in this file Given these options, which one would you recommend and why? Thanks.

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  • PHP 'instanceof' failing with class constant

    - by Nathan Loding
    I'm working on a framework that I'm trying to type as strongly as I possibly can. (I'm working within PHP and taking some of the ideas that I like from C# and trying to utilize them within this framework.) I'm creating a Collection class that is a collection of domain entities/objects. It's kinda modeled after the List<T> object in .Net. I've run into an obstacle that is preventing me from typing this class. If I have a UserCollection, it should only allow User objects into it. If I have a PostCollection, it should only allow Post objects. All Collections in this framework need to have certain basic functions, such as add, remove, iterate. I created an interface, but found that I couldn't do the following: interface ICollection { public function add($obj) } class PostCollection implements ICollection { public function add(Post $obj) {} } This broke it's compliance with the interface. But I can't have the interface strongly typed because then all Collections are of the same type. So I attempted the following: interface ICollection { public function add($obj) } abstract class Collection implements ICollection { const type = 'null'; } class PostCollection { const type = 'Post'; public function add($obj) { if(!($obj instanceof self::type)) { throw new UhOhException(); } } } When I attempt to run this code, I get syntax error, unexpected T_STRING, expecting T_VARIABLE or '$' on the instanceof statement. A little research into the issue and it looks like the root of the cause is that $obj instanceof self is valid to test against the class. It appears that PHP doesn't process the entire self::type constant statement in the expression. Adding parentheses around the self::type variable threw an error regarding an unexpected '('. An obvious workaround is to not make the type variable a constant. The expression $obj instanceof $this->type works just fine (if $type is declared as a variable, of course). I'm hoping that there's a way to avoid that, as I'd like to define the value as a constant to avoid any possible change in the variable later. Any thoughts on how I can achieve this, or have I take PHP to it's limit in this regard? Is there a way of "escaping" or encapsulating self::this so that PHP won't die when processing it?

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  • find a duplicate entry in an array in constant space and O(n) time [closed]

    - by Anubhav Agarwal
    Possible Duplicate: Algorithm to find a duplicate entry in constant space and O(n) time Given an array of N integer such that only one integer is repeated. Find the repeated integer in O(n) time and constant space. There is no range for the value of integers or the value of N For example given an array of 6 integers as 23 45 67 87 23 47. The answer is 23 (I hope this covers ambiguous and vague part) I searched on the net but was unable to find any such question in which range of integers was not fixed. Also here is an example that answers a similar question to mine but here he created a hash table with the highest integer value in C++.But the cpp does not allow such to create an array with 2^64 element(on a 64-bit computer).

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  • Generate a Constant expression from a function

    - by Lee
    For my Google Wave robot, on the onDocumentChanged event I want to apply a filter as follows: @Capability(filter = FILTER) @Override public void onDocumentChanged(DocumentChangedEvent event) { ... } I want the filter to be generated the first time the robot is run, which I'm trying to do as follows: private static final String FILTER = generateFilter(); private static final String generateFilter(){ ... } However, it complains FILTER isn't a constant expression when used within @Capability. generateFilter() will return the same string every time it is called, I'm only using it to create the string so that when I make changes, I don't need to worry about updating the filter. Now I could be going about this all wrong, so wondered if anyone knew what I'm doing wrong, or knew a better way in which I could generate a constant expression from the function.

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  • How to access constant defined in child class?

    - by kavoir.com
    I saw this example from php.net: <?php class MyClass { const MY_CONST = "yonder"; public function __construct() { $c = get_class( $this ); echo $c::MY_CONST; } } class ChildClass extends MyClass { const MY_CONST = "bar"; } $x = new ChildClass(); // prints 'bar' $y = new MyClass(); // prints 'yonder' ?> But $c::MY_CONST is only recognized in version 5.3.0 or later. The class I'm writing may be distributed a lot. Basically, I have defined a constant in ChildClass and one of the functions in MyClass (father class) needs to use the constant. Any idea?

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  • error: switch quantity not an integer

    - by nikeunltd
    I have researched my issue all over StackOverflow and multi-google links, and I am still confused. I figured the best thing for me is ask... Im creating a simple command line calculator. Here is my code so far: const std::string Calculator::SIN("sin"); const std::string Calculator::COS("cos"); const std::string Calculator::TAN("tan"); const std::string Calculator::LOG( "log" ); const std::string Calculator::LOG10( "log10" ); void Calculator::set_command( std::string cmd ) { for(unsigned i = 0; i < cmd.length(); i++) { cmd[i] = tolower(cmd[i]); } command = cmd; } bool Calculator::is_legal_command() const { switch(command) { case TAN: case SIN: case COS: case LOG: case LOG10: return true; break; default: return false; break; } } the error i get is: Calculator.cpp: In member function 'bool Calculator::is_trig_command() const': Calculator.cpp: error: switch quantity not an integer Calculator.cpp: error: 'Calculator::TAN' cannot appear in a constant-expression Calculator.cpp: error: 'Calculator::SIN' cannot appear in a constant-expression Calculator.cpp: error: 'Calculator::COS' cannot appear in a constant-expression The mighty internet, it says strings are allowed to be used in switch statements. Thanks everyone, I appreciate your help.

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  • Rails3 server and bundler error: uninitialized constant Bundler (NameError)

    - by .yandex.rurap-kasta
    I just install rails 3 and all gems that it need, but when I try to start server, it says about problem in boot script. [rap-kasta@acerAspire testR3]$ script/rails server /home/rap-kasta/tmp/testR3/config/boot.rb:7:in `rescue in <top (required)>': uninitialized constant Bundler (NameError) from /home/rap-kasta/tmp/testR3/config/boot.rb:2:in `<top (required)>' from script/rails:9:in `require' from script/rails:9:in `<main> So, I tried to reinstall Bundler, install "pre"-version (but really it has version number lower then i install by gem install bundler Now there are next gems in system: abstract (1.0.0) actionmailer (3.0.0.beta, 2.3.5, 2.3.4) actionpack (3.0.0.beta, 2.3.5, 2.3.4) activemodel (3.0.0.beta) activerecord (3.0.0.beta, 2.3.5, 2.3.4) activeresource (3.0.0.beta, 2.3.5, 2.3.4) activesupport (3.0.0.beta, 2.3.5, 2.3.4) arel (0.2.1, 0.2.pre) builder (2.1.2) bundler (0.9.5) erubis (2.6.5) fxri (0.3.7) fxruby (1.6.20) i18n (0.3.3) jemini (2010.1.24, 2010.1.5) mail (2.1.2) memcache-client (1.7.8) mime-types (1.16) mysql (2.8.1) nifty-generators (0.3.2, 0.3.0) rack (1.1.0, 1.0.1, 1.0.0) rack-mount (0.5.1, 0.4.0) rack-openid (0.2.3, 0.2.2) rack-test (0.5.3) rails (3.0.0.beta, 2.3.5, 2.3.4) railties (3.0.0.beta) rake (0.8.7) rawr (1.3.8) RedCloth (4.2.2) ruby-mysql (3.0.2) ruby-openid (2.1.7) rubygems-update (1.3.5) rubyzip (0.9.4, 0.9.1) rubyzip2 (2.0.1) sqlite3-ruby (1.2.5) text-format (1.0.0) text-hyphen (1.0.0) thor (0.13.2, 0.13.1) tzinfo (0.3.16) Also, there is same error with rails console and similar with bundle check: [rap-kasta@acerAspire testR3]$ bundle check /usr/lib/ruby/gems/1.9.1/gems/bundler-0.9.5/bin/bundle:12:in `rescue in <top (required)>': uninitialized constant Bundler::BundlerError (NameError) from /usr/lib/ruby/gems/1.9.1/gems/bundler-0.9.5/bin/bundle:10:in `<top (required)>' from /usr/bin/bundle:19:in `load' from /usr/bin/bundle:19:in `<main>'

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  • iphone - using NSInvocation: constant value

    - by Mike
    I am dealing with an old iPhone OS 2.x project and I want to keep compatibility, while designing for 3.x. I am using NSInvocation, is a code like this NSInvocation* invoc = [NSInvocation invocationWithMethodSignature: [cell methodSignatureForSelector: @selector(initWithStyle:reuseIdentifier:)]]; [invoc setTarget:cell]; [invoc setSelector:@selector(initWithStyle:reuseIdentifier:)]; int arg2 = UITableViewCellStyleDefault; //???? [invoc setArgument:&arg2 atIndex:2]; [invoc setArgument:&identificadorNormal atIndex:3]; [invoc invoke]; to call 3.0 APIs on 2.0. I am having a problem on the line I marked with question marks. The problem there is that I am trying to assing to arg2, a constant that has not been defined in OS 2.0. As everything with NSInvocation is to do stuff indirectly to avoid compiler errors, how do I set this constant to a variable in an indirect way? Some sort of performSelector "assign value to variable"... is that possible? thanks for any help.

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  • Problem installing mysql gem on Snow Leopard: uninitialized constant MysqlCompat::MysqlRes

    - by emson
    Hi All I've got a problem trying to install the Ruby mysql gem driver. I recently upgraded to Snow Leopard and did the Hivelogic manual install of MySQL. This all seems to work fine as I can access mysql from the command line and make changes to the database. My problem is that if I now use rake db:migrate I get: rake aborted! uninitialized constant MysqlCompat::MysqlRes (See full trace by running task with --trace) Now it appears that my mysql gem isn't working correctly as I can access MySQL fine from Python using the Python driver (which I compiled to). I therefore tried to rebuild the gem using the following command from this site: http://techliberty.blogspot.com/, (incidentally I am using a recent Intel MacBook Pro): sudo env ARCHFLAGS="-arch x86_64" gem install mysql -- --with-mysql-config=/usr/local/mysql/bin/mysql_config This compiles although I get No definition for the documentation: Building native extensions. This could take a while... Successfully installed mysql-2.8.1 1 gem installed Installing ri documentation for mysql-2.8.1... No definition for next_result No definition for field_name ... I'm a little stumped as my mysql_config is located in the correct place: /usr/local/mysql/bin/mysql_config And I have removed all other instances of the mysql gem, from my system. Any suggestions would be greatly appreciated. Many thanks. PS I saw this previous post http://stackoverflow.com/questions/1332207/uninitialized-constant-mysqlcompatmysqlres-using-mms2r-gem but it doesn't seem applicable for my version.

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  • Convert a binary tree to linked list, breadth first, constant storage/destructive

    - by Merlyn Morgan-Graham
    This is not homework, and I don't need to answer it, but now I have become obsessed :) The problem is: Design an algorithm to destructively flatten a binary tree to a linked list, breadth-first. Okay, easy enough. Just build a queue, and do what you have to. That was the warm-up. Now, implement it with constant storage (recursion, if you can figure out an answer using it, is logarithmic storage, not constant). I found a solution to this problem on the Internet about a year back, but now I've forgotten it, and I want to know :) The trick, as far as I remember, involved using the tree to implement the queue, taking advantage of the destructive nature of the algorithm. When you are linking the list, you are also pushing an item into the queue. Each time I try to solve this, I lose nodes (such as each time I link the next node/add to the queue), I require extra storage, or I can't figure out the convoluted method I need to get back to a node that has the pointer I need. Even the link to that original article/post would be useful to me :) Google is giving me no joy. Edit: Jérémie pointed out that there is a fairly simple (and well known answer) if you have a parent pointer. While I now think he is correct about the original solution containing a parent pointer, I really wanted to solve the problem without it :) The refined requirements use this definition for the node: struct tree_node { int value; tree_node* left; tree_node* right; };

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  • Get class constant names in php?

    - by user151841
    I have a php class with some class constants that indicate the status of an instance. When I'm using the class, after I run some methods on it, I do some checks to make sure that the status is what I expect it to be. For instance, after calling some methods, I expect the status to be MEANINGFUL_STATUS_NAME. $objInstance->method1(); $objInstance->method2(); if ( $objInstance->status !== class::MEANINGFUL_STATUS_NAME ) { throw new Exception("Status is wrong, should not be " . class::MEANINGFUL_STATUS_NAME . "."); } However, this gives me the exception message "Status is wrong, should not be 2" when what I really want to see is "Status is wrong, should not be MEANINGFUL_STATUS_NAME" So I've lost the meaningfulness of the constant name. I was thinking of making an 'translation table' array, so I can take the constant values and translate them back into their name, but this seems cumbersome. How should I translate this back, so I get an error message that gives me a better idea of what went wrong?

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  • Plesk + Apache + PHP (FastCGI): Constant session permissions problems, conflicts between HTTP / HTTPS

    - by Hans Engel
    I've just moved a collection of sites over to a brand-new server, running Apache 2.2.3, PHP 5.3, and Plesk 10.1.1. I am having problems with file permissions on PHP sessions, which are being stored in /var/lib/php/session. I originally set the permissions like so for this folder: drwxrwx--- 2 apache psacln 8192 Mar 22 23:25 session This worked fine, for HTTP sessions. Files were being saved in that folder with these permissions: -rw------- 1 client1 psacln 0 Mar 22 23:24 sess_507... -rw------- 1 client2 psacln 0 Mar 22 23:25 sess_8o1... The problem, however, is that PHP scripts accessed via HTTPS do not seem to be run by the same client1 or client2 user. I deleted files in the session directory and accessed a login page via HTTPS to see how sessions were being saved when initiated via this protocol: -rw------- 1 apache apache 0 Mar 22 23:25 sess_507... So, for whatever reason, sessions initiated by clients browsing with HTTPS were being saved by apache:apache, while sessions from HTTP clients were saved with someclient:psacln. What I'd like to ask: How can I avoid this problem with session permissions? When sessions are created via unencrypted HTTP and a client visits an HTTPS portion of the site, permission errors are shown, since apache:apache tries to access the session save created by someclient:psacln. The converse is also true. Can I change the user which runs the Apache HTTPS server, via Plesk or the command line? If not, can I have PHP sessions save with rw-rw---- permissions, and then add apache to the psacln group? Any other suggestions on how to fix this issue?

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  • Installing Wordpress - constant PHP/MySQL extension appears missing

    - by Driss Zouak
    I've got Win2003 w/IIS6, PHP 5 and MySQL installed. I can confirm PHP is installed correctly because I have a testMe.php that runs properly. When I run the Wordpress setup, I get informed that Your PHP installation appears to be missing the MySQL extension which is required by WordPress. But in my PHP.ini in the DYNAMIC EXTENSIONS section I have extension=php_mysql.dll extension=php_mysqli.dll I verified that mysql.dll and libmysql.dll are both in my PHP directory. I copied my libmysql.dll to the C:\Windows\System32 directory. When I try to run the initial setup for WordPress, I get this answer. I've Googled setting this up, and everything comes down to the above. I'm missing something, but none of the instructions that I've found online seem to cover whatever that is.

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  • Switching to a 7200rpm drive -> constant spinning?

    - by LINUX
    Hej Bytte nyligen HD 250GB till 640GB 7200rpm nu har jag bara ca.5 tim battery tid ... och HD snurrar hela tiden. hur kan jag sova ner Hd efter t.ex. 5 minuter ? Tack på förhand. English Translation: I recently switched from a 250GB to 640GB 7200rpm hard drive. Now I only have a 5hr battery life and the hard drive is spinning constantly. How can I spin down the hard drive for, for example, 5 minutes? Thanks in advance.

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  • Constant crashes in windows 7 64bit when playing games

    - by yx
    I've tried everything I can possibly think of in trying to fix this problem and I'm totally out of ideas, so any help would be appreciated: The problem: whenever I fire up a game, it works for a short while with no problems and then it would crash. Either its a hard crash, forcing me to reboot, or windows would report that the display driver has stopped working and recovered. Here is a list of things I've already tried: Drivers - tried the latest drivers (catalyst 9.12) as well as the stock drivers that came with the video card. Also have the latest BIOS/chipset Memtest - Ran Memtest86+ overnight, had no problems, the windows diagnostic tool also does not find any problems. Overheating - Video card/cpu temperatures are well below peak (42 and 31 Celsius receptively) PSU Voltage - CPUID shows that the voltage levels are all above what they should be. The PSU itself is only roughly 16 months old and is a good model. HDD - No errors when checked GPU - Brand new (replaced previous card since I thought it was the problem, apparently not) Overclocking - Everything is at stock levels, memory voltage is set to manufacturer's standard Specs: Motherboard: ASUS P5Q Pro CPU: Core 2 Duo E8400 3.0 ghz OS: Windows 7 home premium 64 bit Memory: Mushkin Enhanced 4GB DDR2 GPU: Sapphire HD 5850 1GB PSU: SeaSonic M12 600W ATX12V DirectX: DX11 Event Viewer after a crash always has these logged: A fatal hardware error has occurred. Reported by component: Processor Core Error Source: Machine Check Exception Error Type: Bus/Interconnect Error Processor ID: 1 The details view of this entry contains further information. A fatal hardware error has occurred. Reported by component: Processor Core Error Source: Machine Check Exception Error Type: Bus/Interconnect Error Processor ID: 0 The details view of this entry contains further information. A previous card that I had (4850x2) also had these errors, so I changed video cards, but the same thing is happening.

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