what's wrong with this map definition?

This is a discussion on what's wrong with this map definition? within the C++ Programming forums, part of the General Programming Boards category; The error is : loganalyzer.cpp: In member function ‘void Loganalyzer::conditionaldistribution(size_t, size_t, size_t, size_t, size_t, double)’: loganalyzer.cpp:1091: error: template argument for ...

  1. #1
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    what's wrong with this map definition?

    The error is :
    loganalyzer.cpp: In member function ‘void Loganalyzer::conditionaldistribution(size_t, size_t, size_t, size_t, size_t, double)’:
    loganalyzer.cpp:1091: error: template argument for ‘template<class _T1, class _T2> struct std:air’ uses local type ‘Loganalyzer::conditionaldistribution(size_t, size_t, size_t, size_t, size_t, double)::Count’
    loganalyzer.cpp:1091: error: trying to instantiate ‘template<class _T1, class _T2> struct std:air’
    loganalyzer.cpp:1091: error: template argument 4 is invalid
    loganalyzer.cpp:1091: error: invalid type in declaration before ‘;’ token


    Code:
    void Loganalyzer::conditionaldistribution(size_t T, size_t S, size_t N, size_t f, size_t SIZE, double alpha) {
    
    	typedef int pathcode;
    
    	typedef struct {
    	public:
    		int countall;
    		int countplus;
    		int countminus;
    	} Count;
    
    	map<pathcode, Count > count;
    ...
    }

  2. #2
    and the hat of sweating
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    Can you post line 1091?
    "I am probably the laziest programmer on the planet, a fact with which anyone who has ever seen my code will agree." - esbo, 11/15/2008

    "the internet is a scary place to be thats why i dont use it much." - billet, 03/17/2010

  3. #3
    Captain Crash brewbuck's Avatar
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    You can't use a function-locally defined type as a template parameter. The message means exactly what it says. Lift the struct definition out to the global scope.
    Code:
    //try
    //{
    	if (a) do { f( b); } while(1);
    	else   do { f(!b); } while(1);
    //}

  4. #4
    and the hat of sweating
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    Interesting... Is there a reason why a function local struct can't be a map member?
    "I am probably the laziest programmer on the planet, a fact with which anyone who has ever seen my code will agree." - esbo, 11/15/2008

    "the internet is a scary place to be thats why i dont use it much." - billet, 03/17/2010

  5. #5
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    Quote Originally Posted by cpjust View Post
    Interesting... Is there a reason why a function local struct can't be a map member?
    Template instances are required to have external linkage, otherwise it would not be possible to instantiate templates without violating the one-definition rule. A side effect of that requirement is that the types used to instantiate a template must also have external linkage. Types that are local to a function do not have external linkage, by definition.
    Right 98% of the time, and don't care about the other 3%.

    If I seem grumpy or unhelpful in reply to you, or tell you you need to demonstrate more effort before you can expect help, it is likely you deserve it. Suck it up, Sunshine, and read this, this, and this before posting again.

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