Usage of STL maps with pointers to member functions

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2 total messages Started by Gabriel Sanchez Gutierrez Tue, 22 Aug 1995 14:01

#1806

Author: Gabriel Sanchez Gutierrez
Date: Tue, 22 Aug 1995 14:01

51 lines
2009 bytes

Hello,

As far as I know, maps are transparent wrt the keys and values stored.
I am trying to maintain a map with pointers to member functions. If I access
the members through normal pointers, all is Ok. But if I use the dictionary,
it seems it is not properly initialized.

Any hint?

#include <iostream.h>
#include <map.h>

typedef char* string;

class Test {
    typedef int  (Test::* pGetM) ();
public:
    int a1;
    int geta1   () {return a1;};

public:
    Test (int a): a1(a) {};
};

main ()
{
    Test t (5);

    Test::pGetM f = Test::geta1;
    
    map<string, Test::pGetM, less<string> > mapMethods;
    mapMethods["a1"]  = f; 

    cout << "Attribut = " << t.a1 << endl
	 << "By map   = " << (t.*f)() << endl;

    cout << "Attribut = " << t.a1 << endl
	 << "By map   = " << (t.*mapMethods["a1"])() << endl;
}


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Re: Usage of STL maps with pointers to member functions

#1823

Author: Bernd Eggink
Date: Wed, 23 Aug 1995 12:42

60 lines
2099 bytes

Gabriel Sanchez Gutierrez (gsg@sema.es) wrote:
>  Hello,

>  As far as I know, maps are transparent wrt the keys and values stored.
>  I am trying to maintain a map with pointers to member functions. If I access
>  the members through normal pointers, all is Ok. But if I use the dictionary,
>  it seems it is not properly initialized.

>  Any hint?

>  #include <iostream.h>
>  #include <map.h>

>  typedef char* string;

>  class Test {
>      typedef int  (Test::* pGetM) ();
>  public:
>      int a1;
>      int geta1   () {return a1;};

>  public:
>      Test (int a): a1(a) {};
>  };

>  main ()
>  {
>      Test t (5);

>      Test::pGetM f = Test::geta1;
>      
>      map<string, Test::pGetM, less<string> > mapMethods;
>      mapMethods["a1"]  = f; 

>      cout << "Attribut = " << t.a1 << endl
>  	 << "By map   = " << (t.*f)() << endl;

>      cout << "Attribut = " << t.a1 << endl
>  	 << "By map   = " << (t.*mapMethods["a1"])() << endl;
>  }

You are comparing pointers instead of strings. Add

  struct less<string>
  {
	bool operator()(string a, string b) { return strcmp(a, b) < 0; }
  };

and it will work.

--
+----------------------------------+
|          Bernd Eggink            |
|    Rechenzentrum Uni Hamburg     |
| admin@rzaix13.rrz.uni-hamburg.de |
+----------------------------------+
---
[ comp.std.c++ is moderated.  Submission address: std-c++@ncar.ucar.edu.
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  is summarized in http://dogbert.lbl.gov/~matt/std-c++/policy.html. ]

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