Templated Classes with Templated Functions

This is a discussion on Templated Classes with Templated Functions within the C++ Programming forums, part of the General Programming Boards category; Based on reading here: Cprogramming.com - Tutorials - Templated Functions I understand that such thing is possible, however I have ...

  1. #1
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    Templated Classes with Templated Functions

    Based on reading here:

    Cprogramming.com - Tutorials - Templated Functions

    I understand that such thing is possible, however I have the following code:

    Code:
    template <int X, int Y>
    class Simulator
    {
    public:
      template<int N, int N1>
      void doom::vector<State, N>& run(doom::vector<Input, N1>& input, double ts);
    protected:
      //some variables here
    }
    
    
    //here's my implementation
    template <int X, int Y>
    template<int N, int N1>
    const doom::vector<State, N>& Simulator<X,Y>::run(doom::vector<Input, N1>& input, double ts);
    {
     //some code here
     return x;
    } 
    
    
    //here's my test
    int main(){
    Simulator<25, 25> s( new Vehicle( WB ) );
    doom::vector<Input, 25> u = InputLibrary::getSimpleInputSet( );
    //this is where the error happened
    doom::vector<State, 25> x = s.run( u, 0.1 );
    }

    my error is the following:
    error: no matching function for call to ‚Simulator<25, 25>::run(ece373::vector<ece373::vector<double, 2>, 25>&, double)‚
    Last edited by -EquinoX-; 11-22-2009 at 04:13 PM.

  2. #2
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    You need to specify the template parameters to run() explicitly because N is not determinable from the parameters.
    It is too clear and so it is hard to see.
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  3. #3
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    I've edited my error above, can you show me what you mean King Mir

  4. #4
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    Code:
    s.run<25,25>( u, 0.1 );
    It is too clear and so it is hard to see.
    A dunce once searched for fire with a lighted lantern.
    Had he known what fire was,
    He could have cooked his rice much sooner.

  5. #5
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    can someone tell me what's wrong with this:

    Code:
    template <int X, int Y>
    Simulator& 
    Simulator<X,Y>::operator=( const Simulator& other )
    {
    	if( &other != this )
    	{
    		delete v;
    		v = new Vehicle();
    		*v = *other.v;
    		x = other.x;
    		u = other.u;
    	}
    	
    	return *this;
    }
    error is

    expected constructor, destructor, or type conversion before ‚&‚ token

  6. #6
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    Code:
    template <int X, int Y>
    Simulator<X, Y>& 
    Simulator<X,Y>::operator=( const Simulator& other )
    I suppose the template arguments are not strictly necessary for the argument (e.g once it becomes clear it is a member function, Simulator will be implicitly treated as Simulator<X, Y>, but you may add it there as well.
    I might be wrong.

    Thank you, anon. You sure know how to recognize different types of trees from quite a long way away.
    Quoted more than 1000 times (I hope).

  7. #7
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    thanks

  8. #8
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    and how do I fix undefined reference errors:

    undefined reference to `Simulator<25, 25>::Simulator(Vehicle*)'
    undefined reference to `Simulator<25, 25>::~Simulator()'

  9. #9
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    You need to define those functions.
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  10. #10
    Algorithm Dissector iMalc's Avatar
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    Quote Originally Posted by -EquinoX- View Post
    can someone tell me what's wrong with this:

    Code:
    template <int X, int Y>
    Simulator& 
    Simulator<X,Y>::operator=( const Simulator& other )
    {
    	if( &other != this )
    	{
    		delete v;
    		v = new Vehicle();
    		*v = *other.v;
    		x = other.x;
    		u = other.u;
    	}
    	
    	return *this;
    }
    Again here is code that checks for self-assignment, which is a bad thing to need to check for. I shall reiterate again that this code is not exception safe because the new statement might throw an exception, but v is already deleted. Then when the Simulator is destructed it would attempt to delete "v" a second time, leading to a fatal program termination. Read these two articles for a full explanation.
    GotW #11: Object Identity
    GotW #23: Object Lifetimes - Part II

    Not only that, but the actual code of the assignment operator really leaves one thinking that there is no point in v being a pointer rather than just a member. Afterall, this assignment operator already assumes that the pointer is not NULL, is dynamically allocated, and has an assignment operator of its own.
    I would suggest making "v" an object rather than a pointer and deleting this assignment operator entirely as everything in the class is then already capable of assignment through the compiler generated version.
    The only reason not to would be if Vehicle doesn't have a non-throwing swap method but Simulator does.
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