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  • C++ vs. C++/CLI: Const qualification of virtual function parameters

    - by James McNellis
    [All of the following was tested using Visual Studio 2008 SP1] In C++, const qualification of parameter types does not affect the type of a function (8.3.5/3: "Any cv-qualifier modifying a parameter type is deleted") So, for example, in the following class hierarchy, Derived::Foo overrides Base::Foo: struct Base { virtual void Foo(const int i) { } }; struct Derived : Base { virtual void Foo(int i) { } }; Consider a similar hierarchy in C++/CLI: ref class Base abstract { public: virtual void Foo(const int) = 0; }; ref class Derived : public Base { public: virtual void Foo(int i) override { } }; If I then create an instance of Derived: int main(array<System::String ^> ^args) { Derived^ d = gcnew Derived; } it compiles without errors or warnings. When I run it, it throws the following exception and then terminates: An unhandled exception of type 'System.TypeLoadException' occurred in ClrVirtualTest.exe Additional information: Method 'Foo' in type 'Derived'...does not have an implementation. That exception seems to indicate that the const qualification of the parameter does affect the type of the function in C++/CLI (or, at least it affects overriding in some way). However, if I comment out the line containing the definition of Derived::Foo, the compiler reports the following error (on the line in main where the instance of Derived is instantiated): error C2259: 'Derived': cannot instantiate abstract class If I add the const qualifier to the parameter of Derived::Foo or remove the const qualifier from the parameter of Base::Foo, it compiles and runs with no errors. I would think that if the const qualification of the parameter affects the type of the function, I should get this error if the const qualification of the parameter in the derived class virtual function does not match the const qualification of the parameter in the base class virtual function. If I change the type of Derived::Foo's parameter from an int to a double, I get the following warning (in addition to the aforementioned error, C2259): warning C4490: 'override': incorrect use of override specifier; 'Derived::Foo' does not match a base ref class method So, my question is, effectively, does the const qualification of function parameters affect the type of the function in C++/CLI? If so, why does this compile and why are there no errors or warnings? If not, why is an exception thrown?

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  • C# - calling ext. DLL function containing Delphi "variant record" parameter

    - by CaldonCZE
    Hello, In external (Delphi-created) DLL I've got the following function that I need to call from C# application. function ReadMsg(handle: longword; var Msg: TRxMsg): longword; stdcall; external 'MyDll.dll' name 'ReadMsg'; The "TRxMsg" type is variant record, defined as follows: TRxMsg = record case TypeMsg: byte of 1: (accept, mask: longword); 2: (SN: string[6]); 3: (rx_rate, tx_rate: word); 4: (rx_status, tx_status, ctl0, ctl1, rflg: byte); end; In order to call the function from C#, I declared auxiliary structure "my9Bytes" containing array of bytes and defined that it should be marshalled as 9 bytes long array (which is exactly the size of the Delphi record). private struct my9Bytes { [MarshalAs(UnmanagedType.ByValArray, ArraySubType = UnmanagedType.U1, SizeConst = 9)] public byte[] data; } Then I declared the imported "ReadMsg" function, using the "my9bytes" struct. [DllImport("MyDll.dll")] private static extern uint ReadMsg(uint handle, ref my9Bytes myMsg); I can call the function with no problem... Then I need to create structure corresponding to the original "TRxMsg" variant record and convert my auxiliary "myMsg" array into this structure. I don't know any C# equivalent of Delphi variant array, so I used inheritance and created the following classes. public abstract class TRxMsg { public byte typeMsg; } public class TRxMsgAcceptMask:TRxMsg { public uint accept, mask; //... } public class TRxMsgSN:TRxMsg { public string SN; //... } public class TRxMsgMRate:TRxMsg { public ushort rx_rate, tx_rate; //... } public class TRxMsgStatus:TRxMsg { public byte rx_status, tx_status, ctl0, ctl1, rflg; //... } Finally I create the appropriate object and initialize it with values manually converted from "myMsg" array (I used BitConverter for this). This does work fine, this solution seems to me a little too complicated, and that it should be possible to do this somehow more directly, without the auxiliary "my9bytes" structures or the inheritance and manual converting of individual values. So I'd like to ask you for a suggestions for the best way to do this. Thanks a lot!

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  • How do i call bash script function using exec function by passing parameter in php?

    - by Stan
    I have created a bash script that install magento in a cpanel. but i have a problem regarding the exec function. $function_path = Mage::getBaseDir()."/media/installer/function.sh"; exec("$function_path $db_host $db_name $db_user $db_pass $url $ad_user $ad_pass $ad_email"); This the bash shell script function.sh #!/bin/bash magento_detail $dbhost $dbname $dbuser $dbpass $url $admin_username $admin_password $admin_email function magento_detail() { stty erase '^?' echo "To install Magento, you will need a blank database ready with a user assigned to it." echo -n "Do you have all of your database information" dbinfo = "y" echo $dbinfo if [ "$dbinfo" -eq 'y' ] then echo "Database Host (usually localhost) : $dbhost " echo "Database Name : $dbname " echo "Database User : $dbuser " echo "Database Password : $dbpass " echo "Store Url : $url " echo "Admin Username : $admin_username " echo "Admin Password : $admin_password " echo "Admin Email Address : $admin_email " echo -n "Include Sample Data? (y/n) " echo sample = "y" if [ "$sample" -eq "y" ]; then echo echo "Now installing Magento with sample data..." echo echo "Downloading packages..." echo wget http://www.magentocommerce.com/downloads/assets/1.5.1.0/magento-1.5.1.0.tar.gz wget http://www.magentocommerce.com/downloads/assets/1.2.0/magento-sample-data-1.2.0.tar.gz echo echo "Extracting data..." echo tar -zxvf magento-1.5.1.0.tar.gz tar -zxvf magento-sample-data-1.2.0.tar.gz echo echo "Moving files..." echo mv magento-sample-data-1.2.0/media/* magento/media/ mv magento-sample-data-1.2.0/magento_sample_data_for_1.2.0.sql magento/data.sql mv magento/index.php magento/.htaccess ./$test1 echo echo "Setting permissions..." echo chmod o+w var var/.htaccess app/etc chmod -R o+w media echo echo "Importing sample products..." echo mysql -h $dbhost -u $dbuser -p$dbpass $dbname < data.sql echo echo "Initializing PEAR registry..." echo chmod 550 mage ./mage mage-setup . echo echo "Downloading packages..." echo echo echo "Cleaning up files..." echo rm -rf downloader/pearlib/cache/* downloader/pearlib/download/* rm -rf magento/ magento-sample-data-1.2.0/ rm -rf magento-1.5.1.0.tar.gz magento-sample-data-1.2.0.tar.gz data.sql rm -rf index.php.sample .htaccess.sample php.ini.sample LICENSE.txt STATUS.txt data.sql echo echo "Installing Magento..." echo php -f install.php --license_agreement_accepted "yes" --locale "en_US" --timezone "America/Los_Angeles" --default_currency "USD" --db_host "$dbhost" --db_name "$dbname" --db_user "$dbuser" --db_pass "$dbpass" --url "$url" --use_rewrites "yes" --use_secure "no" --secure_base_url "" --use_secure_admin "no" --admin_email "$admin_email" --admin_username "$admin_username" --admin_password "$admin_password" echo echo "Finished installing Magento" echo exit else echo "Now installing Magento without sample data..." echo echo "Downloading packages..." echo wget http://www.magentocommerce.com/downloads/assets/1.5.1.0/magento-1.5.1.0.tar.gz echo echo "Extracting data..." echo tar -zxvf magento-1.5.1.0.tar.gz echo echo "Moving files..." echo mv magento/* magento/.htaccess . echo echo "Setting permissions..." echo chmod o+w var var/.htaccess app/etc chmod -R o+w media echo echo "Initializing PEAR registry..." echo chmod 550 mage ./mage mage-setup . echo echo "Downloading packages..." echo echo echo "Cleaning up files..." echo rm -rf downloader/pearlib/cache/* downloader/pearlib/download/* rm -rf magento/ magento-1.5.1.0.tar.gz rm -rf index.php.sample .htaccess.sample php.ini.sample LICENSE.txt STATUS.txt echo echo "Installing Magento..." echo php -f install.php --license_agreement_accepted "yes" --locale "en_US" --timezone "America/Los_Angeles" --default_currency "USD" --db_host "$dbhost" --db_name "$dbname" --db_user "$dbuser" --db_pass "$dbpass" --url "$url" --use_rewrites "yes" --use_secure "no" --secure_base_url "" --use_secure_admin "no" --admin_email "$admin_email" --admin_username "$admin_username" --admin_password "$admin_password" echo echo "Finished installing Magento else part" exit fi else echo "Please setup a database first. Don't forget to assign a database user!" exit fi }` when i run this exec command,at that time it calls bash script function magento_installer() which contains arguments $db_host $db_name $db_user $db_pass $url $ad_user $ad_pass $ad_email. above arguments i'll pass in exec command to call magento_installer() function of bash script. so, is it right way of calling a bash script function? It directly goes to the last step of if condition and prints "Please setup a database first. Don't forget to assign a database user!". It cant enter it in if condition and directly goes to else condition. so please help me?

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  • ruby on rails: How do I access variable data in a url parameter passed to a model?

    - by bandhunt
    I have a variable called "account_type" passed from a rails form and need to access the value in the corresponding model. I can check if :account_type exists as a symbol, but where does the stored data come into play? Is there something I need to do in the controller? This code gives an undefined method 'account_type' error. validates_format_of :name, :with => /^[a-z0-9_]+$/i, :on => :create if account_type == 2 If I use a symbol then it doesn't give an error, but a symbol will never equal 2 validates_format_of :name, :with => /^[a-z0-9_]+$/i, :on => :create if :account_type == 2 It's confusing that you can validate the format of a symbol (like :name above) when :name only seems to be a reference with nothing stored in it. Thanks!

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  • Using Jquery $getJSON How do I dynamically create data for the [data] parameter after Url param?

    - by Breadtruck
    I have no problems getting the Json to work and parse the json return. I was just wondering how I could build a dynamic "whatever data is" and stick it into [data] to pass my parameters from there and not manually append them to the url. From jquery website example: $.getJSON("test.js", { name: "John", time: "2pm" }, function(json){ alert("JSON Data: " + json.users[3].name); }); I thought I could build a string ( which doesn't make sense anyway ) and drop it inside the { }, but I obviously don't understand that part. name: isn't a string and you can't put a variable in that part, so how would I dynamically put items into whatever [data] is.

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  • PHP + MYSQLI: Variable parameter/result binding with prepared statements.

    - by Brian Warshaw
    In a project that I'm about to wrap up, I've written and implemented an object-relational mapping solution for PHP. Before the doubters and dreamers cry out "how on earth?", relax -- I haven't found a way to make late static binding work -- I'm just working around it in the best way that I possibly can. Anyway, I'm not currently using prepared statements for querying, because I couldn't come up with a way to pass a variable number of arguments to the bind_params() or bind_result() methods. Why do I need to support a variable number of arguments, you ask? Because the superclass of my models (think of my solution as a hacked-up PHP ActiveRecord wannabe) is where the querying is defined, and so the find() method, for example, doesn't know how many parameters it would need to bind. Now, I've already thought of building an argument list and passing a string to eval(), but I don't like that solution very much -- I'd rather just implement my own security checks and pass on statements. Does anyone have any suggestions (or success stories) about how to get this done? If you can help me solve this first problem, perhaps we can tackle binding the result set (something I suspect will be more difficult, or at least more resource-intensive if it involves an initial query to determine table structure).

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  • Why is Delphi unable to infer the type for a parameter TEnumerable<T>?

    - by deepc
    Consider the following declaration of a generic utility class in Delphi 2010: TEnumerableUtils = class public class function InferenceTest<T>(Param: T): T; class function Count<T>(Enumerable: TEnumerable<T>): Integer; overload; class function Count<T>(Enumerable: TEnumerable<T>; Filter: TPredicate<T>): Integer; overload; end; Somehow the compiler type inference seems to have problems here: var I: Integer; L: TList<Integer>; begin TEnumerableUtils.InferenceTest(I); // no problem here TEnumerableUtils.Count(L); // does not compile: E2250 There is no overloaded version of 'Count' that can be called with these arguments TEnumerableUtils.Count<Integer>(L); // compiles fine end; The first call works as expected and T is correctly inferred as Integer. The second call does not work, unless I also add <Integer -- then it works, as can be seen in the third call. Am I doing something wrong or is the type inference in Delphi just not supporting this (I don't think it is a problem in Java which is why expected it to work in Delphi, too).

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  • Function with parameter type that has a copy-constructor with non-const ref chosen?

    - by Johannes Schaub - litb
    Some time ago I was confused by the following behavior of some code when I wanted to write a is_callable<F, Args...> trait. Overload resolution won't call functions accepting arguments by non-const ref, right? Why doesn't it reject in the following because the constructor wants a Test&? I expected it to take f(int)! struct Test { Test() { } // I want Test not be copyable from rvalues! Test(Test&) { } // But it's convertible to int operator int() { return 0; } }; void f(int) { } void f(Test) { } struct WorksFine { }; struct Slurper { Slurper(WorksFine&) { } }; struct Eater { Eater(WorksFine) { } }; void g(Slurper) { } void g(Eater) { } // chooses this, as expected int main() { // Error, why? f(Test()); // But this works, why? g(WorksFine()); } Error message is m.cpp: In function 'int main()': m.cpp:33:11: error: no matching function for call to 'Test::Test(Test)' m.cpp:5:3: note: candidates are: Test::Test(Test&) m.cpp:2:3: note: Test::Test() m.cpp:33:11: error: initializing argument 1 of 'void f(Test)' Can you please explain why one works but the other doesn't?

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  • c# create an arbitrary length generic parameter string e.g. ?,?,?

    - by Sky Sanders
    I know I am forgetting to remember how to do this and it is late. I want to, in an elegant manner, build a placeholder list for a munged sql command. Have a command with an arbitrary number of parameters, need to build ?,?,? Did I mention that it was a wet brain fart? this is what came out: Regex.Replace(new string('?', _command.Parameters.Count), @"\?\?", @"\?,\?"); You are welcome to make me feel like more of an idiot if you just remember me what I am forgetting. ;-)

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  • [SCORM 2004] the cmi.total_time parameter does not return anything.

    - by Nephila
    I am programming a SCORM 2004 product. I can update the session_time, it works. I can set the status (passed, failed, etc...) I also can get the cmi.location time. No problems! But I don't succeed atingt get the total time (cmi.total_time). I have tested on 2 LMS: On Ganesha the API.GetValue('cmi.total_time') is an empty string. On Moodle the API.GetValue('cmi.total_time') is just a "P". I do have the correct logs with correct session times. EDIT. I also try on cloud.scorm.com and cmi.total_time returns each time PT0H0M0S.

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  • Can I automate the finding of -l parameter I use when linking based on header files (gcc)?

    - by kavic
    Normally when linking against a static library, I have to specify a library directory and the name of a libX.so (or its symbolic link) as -lX flag for linking [and its directory with -L flag]. Can I automate this based on my header files (in c/c++) only? Or maybe it is not a good idea? Is there a software for locating the -L and -l parameters automatically? Is some table stored somewhere on the system about this on popular linux systems or even cygwin?

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  • Search sort by parameter match count in the query? PostgreSQL

    - by Ben Dauphinee
    I am working on a search query in PostgreSQL, and one of the things I do is sort my query results by the number of parameters matched. I have no clue how this can be done. Does anyone have a suggestion or solution? Table brand color type engine Ford Blue 4-door V8 Maserati Blue 2-door V12 Saturn Green 4-door V8 GM Yellow 1-door V4 Current Query SELECT brand FROM table WHERE color = 'Blue' or type = '4-door' or engine = 'V8' Result Should Be Ford (3 match) Saturn (2 match) Maserati (1 match)

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  • django + south + python: strange behavior when using a text string received as a parameter in a func

    - by carlosescri
    Hello, this is my first question. I'm trying to execute a SQL query in django (south migration): from django.db import connection # ... class Migration(SchemaMigration): # ... def transform_id_to_pk(self, table): try: db.delete_primary_key(table) except: pass finally: cursor = connection.cursor() # This does not work cursor.execute('SELECT MAX("id") FROM "%s"', [table]) # I don't know if this works. try: minvalue = cursor.fetchone()[0] except: minvalue = 1 seq_name = table + '_id_seq' db.execute('CREATE SEQUENCE "%s" START WITH %s OWNED BY "%s"."id"', [seq_name, minvalue, table]) db.execute('ALTER TABLE "%s" ALTER COLUMN id SET DEFAULT nextval("%s")', [table, seq_name + '::regclass']) db.create_primary_key(table, ['id']) # ... I use this function like this: self.transform_id_to_pk('my_table_name') So it should: Find the biggest existent ID or 0 (it crashes) Create a sequence name Create the sequence Update the ID field to use sequence Update the ID as PK But it crashes and the error says: File "../apps/accounting/migrations/0003_setup_tables.py", line 45, in forwards self.delegation_table_setup(orm) File "../apps/accounting/migrations/0003_setup_tables.py", line 478, in delegation_table_setup self.transform_id_to_pk('accounting_delegation') File "../apps/accounting/migrations/0003_setup_tables.py", line 20, in transform_id_to_pk cursor.execute(u'SELECT MAX("id") FROM "%s"', [table.encode('utf-8')]) File "/Library/Python/2.6/site-packages/django/db/backends/util.py", line 19, in execute return self.cursor.execute(sql, params) psycopg2.ProgrammingError: relation "E'accounting_delegation'" does not exist LINE 1: SELECT MAX("id") FROM "E'accounting_delegation'" ^ I have shortened the file paths for convenience. What does that "E'accounting_delegation'" mean? How could I get rid of it? Thank you! Carlos.

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  • What's the standard behaviour for an out parameter when a TryXxxx method returns false?

    - by Matt Lacey
    Assuming a method with the following signature bool TryXxxx(object something, out int toReturn) What is it acceptable for toReturn to be if TryXxxx returns false? In that it's infered that toReturn should never be used if TryXxxx fails does it matter? If toReturn was a nulable type, then it would make sense to return null. But int isn't nullable and I don't want to have to force it to be. If toReturn is always a certain value if TryXxxx fails we risk having the position where 2 values could be considered to indicate the same thing. I can see this leading to potential possible confusion if the 'default' value was returned as a valid response (when TryXxxx returns true). From an implementation point if view it looks like having toReturn be a[ny] value is easiest, but is there anything more important to consider?

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  • Why does sh/bash set command line parameter values when trying to set environment variable?

    - by Touko
    A question on basics : While tuning environment variables for a program launched from a script, I ended up with somewhat strange behaviour with sh (which seems to be actually linked to bash) : variable setting seems to mess up with command-line parameters. Could somebody explain why does this happen? A simple script: #! /bin/sh # Messes with $1 ?? set ANT_OPTS=-Xmx512M export ANT_OPTS # Works # export ANT_OPTS=-Xmx512M echo "0 = $0" echo "1 = $1" When I run this with the upper alternative (set + export), the result is as following: $ ./test.sh foo 0 = ./test.sh 1 = ANT_OPTS=-Xmx512M But with lower alternative (export straight), the result is as I supposed: $ ./test.sh foo 0 = ./test.sh 1 = foo There is surely logical explanation, I just haven't figured it out yet. Somebody who does have idea? br, Touko

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  • Reference Value Parameter VS Return value which one is good?

    - by CodeYun
    When we want to modify some value in one object we may use two different methods, just want to know which one is better or there is no big different between them. void SomeMethod() { UserInfo newUser = New UserInfo(); ModifyUserInfo(newUser); //Modify UserInfo after calling void method GetUserInfo } void ModifyUserInfo(UseerInfo userInfo) { userInfo.UserName = "User Name"; ..... } void SomeMethod() { UserInfo newUser = New UserInfo(); //Assign new userinfo explicitly newUser = GetUserInfo(newUser); } UserInfo ModifyUserInfo(UseerInfo userInfo) { userInfo.UserName = "User Name"; ..... return userInfo; }

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  • How to pass associative Array parameter from javascript to ActiveX object?

    - by Rory
    I'd like to pass an associative array (or simply an object with property names & values) to my ActiveXObject. I can't find anyone who has successfully and simply passed complex data from javascript to an ActiveX object. My ActiveX object is being loaded in IE, and it's mine so I can change the method signature & code to whatever will work. I also have control over the structure of the javascript. Without a simple way of doing this I'm thinking of url-encoding the data and sending it as a string. But that does seem a little silly if it's possible just to pass an object. The ActiveX object is coded in C# if that makes any difference...

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  • Does it ever make sense to make a fundamental (non-pointer) parameter const?

    - by Scott Smith
    I recently had an exchange with another C++ developer about the following use of const: void Foo(const int bar); He felt that using const in this way was good practice. I argued that it does nothing for the caller of the function (since a copy of the argument was going to be passed, there is no additional guarantee of safety with regard to overwrite). In addition, doing this prevents the implementer of Foo from modifying their private copy of the argument. So, it both mandates and advertises an implementation detail. Not the end of the world, but certainly not something to be recommended as good practice. I'm curious as to what others think on this issue. Edit: OK, I didn't realize that const-ness of the arguments didn't factor into the signature of the function. So, it is possible to mark the arguments as const in the implementation (.cpp), and not in the header (.h) - and the compiler is fine with that. That being the case, I guess the policy should be the same for making local variables const. One could make the argument that having different looking signatures in the header and source file would confuse others (as it would have confused me). While I try to follow the Principle of Least Astonishment with whatever I write, I guess it's reasonable to expect developers to recognize this as legal and useful.

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