How do I define a pointer to a function which returns a char pointer?

Ans:

char * ( *p )( ) ;  

or  

typedef char * ( * ptrtofun )( ) ;  

ptrtofun p ;

Here is a sample program which uses this definition. 

main( )  

{  

typedef char * ( * ptrtofun ) ( ) ;  

char * fun( ) ;  

ptrtofun fptr ;  

char *cptr ;  

fptr = fun ;  

cptr = (*fptr) ( ) ;  

printf ( "\nReturned string is \"%s\"", cptr ) ;  

}  

char * fun( )  

{  

static char s[ ] = "Hello!" ;  

printf ( "\n%s", s ) ;  

return s ;  

}

When we are required to find offset of an element within a structure? or, how do we call the function of an outer class from a function in the inner class? (The inner class is nested in the outer class)

Ans:

#include  <iostream.h> 

class outer  

{ 

int i ;  

float f ; 

public : 

class inner  

{ 

public : 

infunc( )  

{ 

outer *pout ;  

pout = (outer*) this - ( size_t ) &( ( ( outer* ) 0 ) -> in ) ;  

pout -> outfunc( ) ; 

} 

} ;  

inner in ;  

outfunc( )  

{ 

cout << "in outer class's function" ; 

} 

} ;  

void main( )  

{ 

outer out ;  

out.in.infunc( )  

}

In the above example we are calling outer::outfunc( ) from inner::infunc( ). Tocall outfunc( ) we need a pointer to the outer class. To get the pointer we have subtracted offset of the inner class's object (base address of outer class's object - address of inner class's object) from address of inner class's object.