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  • Postgresql constraint

    - by Ryan
    I cannot seem to get this right, I am trying to modify a field to be a foreign key, with cascading delete... what am i doing wrong? ALTER TABLE my_table ADD CONSTRAINT $4 FOREIGN KEY my_field REFERENCES my_foreign_table ON DELETE CASCADE;

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  • Processing an XML file removes comments

    - by little
    This snippet <!--Please don't delete this--> is part of my xml file. After running this method, the resulting xml file does not contain this snippet anymore <!--Please don't delete this-->. Why is this? Here's my method: XmlSerializer serializer = new XmlSerializer(typeof(Settings)); TextWriter writer = new StreamWriter(path); serializer.Serialize(writer, settings); writer.Close();

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  • C++ - Print Out Objects From Set

    - by John Smith
    If I have a C++ set, declaration set personList; with iterator, set::const_iterator location; how can I print out the contents of the set? They are all person objects, and I have overridden the operator<< for Person. The line that errors is: cout << location and it's in a basic for loop. Netbeans gives the following error: proj.cpp:78: error: no match for ‘operator<<’ in ‘std::cout << location’ so it looks like it wants an override for the iterator's <<. Basically, I am taking objects that used to be stored in an array format, but are now in a set. What is the equivalent to cout << array[i] for sets?

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  • Using a class with const data members in a vector

    - by Max
    Given a class like this: class Foo { const int a; }; Is it possible to put that class in a vector? When I try, my compiler tells me it can't use the default assignment operator. I try to write my own, but googling around tells me that it's impossible to write an assignment operator for a class with const data members. One post I found said that "if you made [the data member] const that means you don't want assignment to happen in the first place." This makes sense. I've written a class with const data members, and I never intended on using assignment on it, but apparently I need assignment to put it in a vector. Is there a way around this that still preserves const-correctness?

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  • Is there a command to test an SQL query without executing it? ( MySQL or ANSI SQL )

    - by Petruza
    Is there anything like this: TEST DELETE FROM user WHERE somekey = 45; That can return any errors, for example that somekey doesn't exist, or some constraint violation or anything, and reporting how many rows would be affected, but not executing the query? I know you can easily turn any query in a select query that has no write or delete effect in any row, but that can lead to errors and it's not very practical if you want to test and debug many queries.

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  • non-scalar type requested

    - by lego69
    can somebody please help me with an error conversion from `A' to non-scalar type `B' requested I have class A and derived from it B, but I have problems with these rows: A a(1); A *pb = new B(a); B b = *pb; //here I have an error thanks in advance for any help class A { protected: int player; public: A(int initPlayer = 0); A(const A&); A& operator=(const A&); virtual ~A(){}; virtual void foo(); void foo() const; operator int(); }; class B: public A { public: B(int initPlayer): A(initPlayer){}; ~B(){}; virtual void foo(); };

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  • Library for Dataflow in C

    - by msutherl
    How can I do dataflow (pipes and filters, stream processing, flow based) in C? And not with UNIX pipes. I recently came across stream.py. Streams are iterables with a pipelining mechanism to enable data-flow programming and easy parallelization. The idea is to take the output of a function that turns an iterable into another iterable and plug that as the input of another such function. While you can already do this using function composition, this package provides an elegant notation for it by overloading the operator. I would like to duplicate a simple version of this kind of functionality in C. I particularly like the overloading of the operator to avoid function composition mess. Wikipedia points to this hint from a Usenet post in 1990. Why C? Because I would like to be able to do this on microcontrollers and in C extensions for other high level languages (Max, Pd*, Python). * (ironic given that Max and Pd were written, in C, specifically for this purpose – I'm looking for something barebones)

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  • Not a statement?

    - by abelenky
    I have a simple little code fragment that is frustrating me: HashSet<long> groupUIDs = new HashSet<long>(); groupUIDs.Add(uid)? unique++ : dupes++; At compile time, it generates the error: Only assignment, call, increment, decrement, and new object expressions can be used as a statement HashSet.Add is documented to return a bool, so the ternary (?) operator should work, and this looks like a completely legitimate way to track the number of unique and duplicate items I add to a hash-set. When I reformat it as a if-then-else, it works fine. Can anyone explain the error, and if there is a way to do this as a simple ternary operator?

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  • How can I move deleting photos to the background with delayed_job and paperclip

    - by Tam
    I let my users create photo albums with many photos. Relationship as follows: has_many :album_photos, :dependent => :destroy i upload photos to S3 When the user delete album I want to delete all photos as the relationship shows but it takes time if the user has many photos. Can I automatically set photo deletion to happen in the background (delayed_job) without having to manually call 'send_later' on every photo?

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  • C++ enumaration

    - by asli
    Hi,my question is about enumaration,my codes are : #include<iostream> using namespace std; int main() { enum bolumler{programcilik,donanim,muhasebe,motor,buro} bolum; bolum = donanim; cout<<bolum<<endl; bolum+=2; /* bolum=motor */ cout<<bolum; return 0; } The output should be 1 3 but according to these codes the error is: error C2676: binary '+=' : 'enum main::bolumler' does not define this operator or a conversion to a type acceptable to the predefined operator Error executing cl.exe. 111.obj - 1 error(s), 0 warning(s) Can you help me ?The other question is what can I do if I want to see the output like that "muhasebe"?

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  • Deleting Row Method on GridView

    - by George
    I am trying to implement the deleting method and pass my parameters for the delete operation. I am using sqldatasource. Since the ID doesnt have a column in my gridview how can I get the value of the ID and set it as my delete parameter?

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  • Create a ASP.NET smart gridview

    - by harold-sota
    I wont to create a User Control based in gridview that have the edit add delete incorporate, the problem is these: In the admin part of my web site i have to repeat the same action for view add delete update the data for different datasource. I wont to create a generic gridview that have incorporate these action. The gridview can take a xml file for configure him self dependently of the request for desplay the data. Any ideas how i can do it?

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  • How to bind a label inside a gridview to another table?

    - by Kolten
    I have a very standard Gridview, with Edit and Delete buttons auto-generated. It is bound to a tableadapter which is linked to my "RelationshipTypes" table. dbo.RelationshipTypes: ID, Name, OriginConfigTypeID, DestinationConfigTypeID I wish to use a label that will pull the name from the ConfigTypes table, using the "OriginConfigTypeID" and "DestinationTypeID" as the link. dbo.ConfigTypes: ID, Name My problem is, I can't automatically generate Edit and Delete buttons using an Inner Join in my dataset. Or can I? FOllowing is my code: <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" AutoGenerateDeleteButton="True" AutoGenerateEditButton="True" CssClass="TableList" DataKeyNames="ID" DataSourceID="dsRelationShipTypes1"> <Columns> <asp:BoundField DataField="ID" HeaderText="ID" InsertVisible="False" ReadOnly="True" SortExpression="ID" Visible=False/> <asp:TemplateField HeaderText="Origin" SortExpression="OriginCIType_ID"> <EditItemTemplate> &nbsp;<asp:DropDownList Enabled=true ID="DropDownList2" runat="server" DataSourceID="dsCIType1" DataTextField="Name" DataValueField="ID" SelectedValue='<%# Bind("OriginCIType_ID") %>'> </asp:DropDownList> </EditItemTemplate> <ItemTemplate> &nbsp; <asp:Label ID="Label2" runat="server" Text='<%# Bind("OriginCIType_ID") %>'></asp:Label> </ItemTemplate> </asp:TemplateField> <asp:TemplateField HeaderText="Name" SortExpression="Name"> <EditItemTemplate> <asp:TextBox ID="TextBox3" runat="server" Text='<%# Bind("Name") %>'></asp:TextBox> </EditItemTemplate> <ItemTemplate> <asp:Label ID="Label3" runat="server" Text='<%# Bind("Name") %>'></asp:Label> </ItemTemplate> </asp:TemplateField> <asp:TemplateField HeaderText="Destination" SortExpression="DestinationCIType_ID"> <EditItemTemplate> <asp:DropDownList ID="DropDownList3" runat="server" DataSourceID="dsCIType1" DataTextField="Name" DataValueField="ID" SelectedValue='<%# Bind("DestinationCIType_ID") %>'> </asp:DropDownList> </EditItemTemplate> <ItemTemplate> <asp:Label ID="Label1" runat="server" Text='<%# Bind("DestinationCIType_ID") %>'></asp:Label> </ItemTemplate> </asp:TemplateField> </Columns> </asp:GridView> So I did try to create my own edit and delete buttons, but kept receiving the error "cannot find update method" or something similar. Do I have to manually code the delete and update methods in my code-behind?

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  • C++ function object terminology functor, deltor, comparitor, etc..

    - by Robert S. Barnes
    Is there a commonly accepted terminology for various types for common functors? For instance I found myself naturally using comparitor for comparison functors like this: struct ciLessLibC : public std::binary_function<std::string, std::string, bool> { bool operator()(const std::string &lhs, const std::string &rhs) const { return strcasecmp(lhs.c_str(), rhs.c_str()) < 0 ? 1 : 0; } }; Or using the term deltor for something like this: struct DeleteAddrInfo { void operator()(const addr_map_t::value_type &pr) const { freeaddrinfo(pr.second); } }; If using these kinds of shorthand terms is common, it there some dictionary of them all someplace?

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  • What is the difference between the * and the & operators in c programming?

    - by Wesley
    I am just making sure I understand this concept correctly. With the * operator, I make a new variable, which is allocated a place in memory. So as to not unnecessarily duplicate variables and their values, the & operator is used in passing values to methods and such and it actually points to the original instance of the variable, as opposed to making new copies...Is that right? It is obviously a shallow understanding, but I just want to make sure I am not getting them mixed up. Thanks!

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  • problem in deleting record

    - by akshay
    I have a entity manager em1 .em1 starts a transcation tx on db1 table1.Now inside tx i call a API getdata().This API creastes a new entitymanger em2 and return 1 record.Now if entity manger em1 tries to delete the record returned by em1 , it hangs.Code times out.Is the record locked by em1.How can ii solve this problem? create em1 //em1 start transcation tx1 tx1.start Object r = getData(); em1 tried to delete r //code hangs here tx1.commit Object getData(){ create em2 return data found using em2 }

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  • C++ return type overload hack

    - by aaa
    I was bored and came up with such hack (pseudocode): 1 struct proxy { 2 operator int(); // int function 3 operator double(); // double function 4 proxy(arguments); 5 arguments &arguments_; 6 }; 7 8 proxy function(arguments &args) { 9 return proxy(args); 10 } 11 int v = function(...); 12 double u = function(...); is it evil to use in real code?

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  • Why does this simple bash code give a syntax error?

    - by Tim
    I have the following bash code, which is copied and pasted from "bash cookbook" (1st edition): #!/bin/bash VERBOSE=0; if [[ $1 =-v ]] then VERBOSE=1; shift; fi When I run this (bash 4.0.33), I get the following syntax error: ./test.sh: line 4: conditional binary operator expected ./test.sh: line 4: syntax error near `=-v' ./test.sh: line 4: `if [[ $1 =-v ]]' Is this as simple as a misprint in the bash cookbook, or is there a version incompatibility or something else here? What would the most obvious fix be? I've tried various combinations of changing the operator, but I'm not really familiar with bash scripting.

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  • Fast comparison of char arrays?

    - by StackedCrooked
    I'm currently working in a codebase where IPv4 addresses are represented as pointers to u_int8. The equality operator is implemented like this: bool Ipv4Address::operator==(const u_int8 * inAddress) const { return (*(u_int32*) this->myBytes == *(u_int32*) inAddress); } This is probably the fasted solution, but it causes the GCC compiler warning: ipv4address.cpp:65: warning: dereferencing type-punned pointer will break strict-aliasing rules How can I rewrite the comparison correctly without breaking strict-aliasing rules and without losing performance points? I have considered using either memcmp or this macro: #define IS_EQUAL(a, b) \ (a[0] == b[0] && a[1] == b[1] && a[2] == b[2] && a[3] == b[3]) I'm thinking that the macro is the fastest solution. What do you recommend?

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  • boost variant static_visitor problem picking correct function

    - by Steve
    I'm sure I'm having a problem with template resolution here, but I'm not sure why I'm having the problem. I have a static visitor I'm passing to boost variant where i've had to do template specialization for certain cases. The case for everything except for MyClass should throw in the static_visitor below. Unfortunately, when the visitor is applied to pull a MyClass out, it selects the most generic case rather than the exact match. I would type each case explicitly, but that will be rather long. So, why is the compiler resolving the most generic case over the exact match, and is there anyway to fix it template<> class CastVisitor<MyClass>:public boost::static_visitor<MyClass> { public: template<typename U> MyClass operator()(const U & i) const { throw std::exception("Unable to cast"); } MyClass operator()(const MyClass& i) { return i; } };

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  • C++ struct sorting error

    - by Betamoo
    I am trying to sort a vector of custom struct in C++ struct Book{ public:int H,W,V,i; }; with a simple functor class CompareHeight { public: int operator() (Book lhs,Book rhs) { return lhs.H-rhs.H; } }; when trying : vector<Book> books(X); ..... sort(books.begin(),books.end(), CompareHeight()); it gives me exception "invalid operator <" What is the meaning of this error? Thanks

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  • Encrypt/ Decrypt text file in Delphi?

    - by Hemant Kothiyal
    Hi i would like to know best encryption technique for text file encryption and ecryption. My Scenario: I have software having two type of users Administartor and Operators. Our requirement is to encrypt text file when Administrator enter data using GUI and save it. That encrypted file would be input for Operator and they just need to select it and use that file. Here file should be automatically decrypt data for further calculation when Operator select those files. Please help me which encryption/ decryption technique should i use?

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