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From: robert@ireq.hydro.qc.ca (R.Meunier 8516)
Newsgroups: comp.lang.c++
Subject: Pointer to function
Message-ID: <3194@s3.ireq.hydro.qc.ca>
Date: 1 Oct 90 18:08:01 GMT
Sender: root@s3.ireq.hydro.qc.ca
Reply-To: robert@ireq.hydro.qc.ca ()
Organization: IREQ, Hydro-Quebec
Lines: 150



	I'm trying to implement a stack objet with ptr to function
as members. But i can't go through the compiler (SUN C++)

Here is a part of the code, can someone point me out what is
wrong.


--------------------------------------------------------------------


#include <stream.h>


class ST
{
	void *data;
	void (*ptrFct)(void *);
public:
	ST(void *, void (*)(void *));
	void exec();
};

ST::ST(void *d, void (*ptr)(void *))
{
	data = d;
	ptrFct = ptr;
}

void ST::exec()
{
	(*ptrFct)(data);
}

void foo1(int *a)
{
	*a += 1;
}

void foo2(float *a)
{
	*a += 1;
}

main()
{
int aa=10;
float bb=100;

void foo1(int *);
void foo2(float *);

ST a(&aa,foo1);
ST b(&bb,foo2);

	a.exec();	
	a.exec();
}


--------------------------------------------------------------------

	I get those error message from the compiler:
"p1.cc", line 44: error:
	bad argument  2 type for ST::ST(): void (*)(int *) ( void (*)(void *) expected)
"p1.cc", line 45: error:
	bad argument  2 type for ST::ST(): void (*)(float *) ( void (*)(void *) expected)


	so i have not define the parameter by putting (...) like that

--------------------------------------------------------------------
#include <stream.h>


class ST
{
	void *data;
	void (*ptrFct)(...);
public:
	ST(void *, void (*)(...));
	void exec();
};

ST::ST(void *d, void (*ptr)(...))
{
	data = d;
	ptrFct = ptr;
}

void ST::exec()
{
	(*ptrFct)(data);
}

void foo1(int *a)
{
	*a += 1;
}

void foo2(float *a)
{
	*a += 1;
}

main()
{
int aa=10;
float bb=100;

void foo1(...);
void foo2(...);

ST a(&aa,foo1);
ST b(&bb,foo2);

	a.exec();	
	a.exec();
}



--------------------------------------------------------------------


   With that code, i get ld: Undefined symbol 
                             _foo1()    
                             _foo2()   

	because the compiler is trying to overload foo1 and foo2 since the
parameter do not match.

	What should i do?

P.S. In case you are wondering what i am trying to do, i am implemanting
a small task library that will collect ptr to data and ptr to function
and execute them later. The function are always of the form:

Function(DATA *ptr)
{
}

with function and DATA undefined by the task manager (declare as void *)

--
-----------------------------------------------------------------------
Robert Meunier                     Institut de Recherche d'Hydro-Quebec
Ingenieur                          1800 Montee Ste-Julie, Varennes
Internet: robert@ireq.hydro.qc.ca  Qc, Canada, J3X 1S1