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Jun 27th, 2007

Reg Function pointers

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Hi All,

I am trying to implement the concept of function pointer in C++.
While compiling i got some errors which I couldnt figure out the reason .
So,Please let me know what changes should be done for resolving that error.

I am trying to execute one particular command function when the commandis pressed.Likewise, I have 100 commands and whenever the commands are pressed the corresponding function + arguements should be passed and the function pointer should execute the command.

Below are my code,

C++ Syntax (Toggle Plain Text)
command.h
**********
#define FUNCPTR  void *
#define MAX_NUM_COMMANDS 3
 
typedef struct
{
   char command[LINELEN];                           /* name of the command */
   char parm1[LINELEN];                             /*parameter 1 */
   char parm2[LINELEN];                             /*parameter 2 */
 
} ExeCmd_s;
class FunctionEntry
{
 
public:
    char* commandString;
    FUNCPTR pFun;   
    int SearchCommand(char* command);
};
FunctionEntry funArr[MAX_NUM_COMMANDS]=
{
	    {"aaa",(FUNCPTR)aaa},
            {"bbb", (FUNCPTR)bbb},
   	    {"ccc",(FUNCPTR)ccc}
 
};
enum commandName
{
	aaa = 0,
	bbb
};
 
 
command.c
**********
void void Execute ()
{
  .........
  .........
 Execmd execmd;
 FunctionEntry command;
 int rc;
 if(0 != SearchCommand(exeCmd.command))
 {
    command = FunctionEntry.SearchCommand(exeCmd.command);
    switch((int)command.numOfArguements)
    {
         case Zero :
           rc = ((command.pFun)();
           break;
	 case one:
	   rc = ((command.pFun),exeCmd.parm1);
	   break;
    }
 }
 else
 {
   printf("No match");
 }
 
}
 
 
 
//Function to search and returns the index of the command
 
int FunctionEntry :: SearchCommand(char* command)
{
 
     ExeCmd_s exeCmd;  //already had a Structure where I am extracting the commandname..
     int index = 0;     
     while(index < MAX_NUM_COMMANDS)
     {
	 if(strcmp(exeCmd.command,funArr[index]) == 0)
	 {
	    return &funArr[index];
	 }
         index++;	
    }
     return NULL;
}
command.h
**********
#define FUNCPTR  void *
#define MAX_NUM_COMMANDS 3

typedef struct
{
   char command[LINELEN];                           /* name of the command */
   char parm1[LINELEN];                             /*parameter 1 */
   char parm2[LINELEN];                             /*parameter 2 */
                                      
} ExeCmd_s;
class FunctionEntry
{

public:
    char* commandString;
    FUNCPTR pFun;   
    int SearchCommand(char* command);
};
FunctionEntry funArr[MAX_NUM_COMMANDS]=
{
	    {"aaa",(FUNCPTR)aaa},
            {"bbb", (FUNCPTR)bbb},
   	    {"ccc",(FUNCPTR)ccc}

};
enum commandName
{
	aaa = 0,
	bbb
};


command.c
**********
void void Execute ()
{
  .........
  .........
 Execmd execmd;
 FunctionEntry command;
 int rc;
 if(0 != SearchCommand(exeCmd.command))
 {
    command = FunctionEntry.SearchCommand(exeCmd.command);
    switch((int)command.numOfArguements)
    {
         case Zero :
           rc = ((command.pFun)();
           break;
	 case one:
	   rc = ((command.pFun),exeCmd.parm1);
	   break;
    }
 }
 else
 {
   printf("No match");
 }

}



//Function to search and returns the index of the command

int FunctionEntry :: SearchCommand(char* command)
{
     
     ExeCmd_s exeCmd;  //already had a Structure where I am extracting the commandname..
     int index = 0;     
     while(index < MAX_NUM_COMMANDS)
     {
	 if(strcmp(exeCmd.command,funArr[index]) == 0)
	 {
	    return &funArr[index];
	 }
         index++;	
    }
     return NULL;
}

Please let me know where i should change the code.
Expecting some solutions for this code ASAP .

Thanks,
Sowmi

Last edited by WaltP; Jun 27th, 2007 at 2:42 pm. Reason: Use the PREVIEW button to see if your post looks correct.

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sowmi

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since Jun 2007

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Jun 27th, 2007

Re: Reg Function pointers

Click to Expand / Collapse Quote originally posted by sowmi ...

Hi All,

I am trying to implement the concept of function pointer in C++.
While compiling i got some errors which I couldnt figure out the reason .
So,Please let me know what changes should be done for resolving that error.

Which errors? Without posting them, we have no idea what the errors are.

Click to Expand / Collapse Quote originally posted by sowmi ...

I am trying to execute one particular command function when the commandis pressed.Likewise, I have 100 commands and whenever the commands are pressed the corresponding function + arguements should be passed and the function pointer should execute the command.

Without a clean compile, this info is moot.

Click to Expand / Collapse Quote originally posted by sowmi ...

Below are my code,

Below is my code. Code is singular in programming.

WaltP

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Posting Sage

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since May 2006

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Jun 27th, 2007

Re: Reg Function pointers

I see no definition for public function
int SearchCommand()
in class FunctionEntry.

I suppose that might stop you dead in your tracks!

JRM

Reputation Points: 130

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since Oct 2006

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Jun 28th, 2007

Re: Reg Function pointers

Click to Expand / Collapse Quote originally posted by sowmi ...

...I have 100 commands and whenever the commands are pressed the corresponding function + arguements...

it is much more flexible to represent functions as objects . this would allow free functions, function objects and member functions to be treated polymorphically. also, since these are objects, they can support operations (eg.bind). in the following example, boost.function and boost.bind are used (from the boost libraries); however, both function and bind would be part of c++0x (they are in tr1).

C++ Syntax (Toggle Plain Text)
#include <iostream>
#include <boost/function.hpp>
#include <boost/bind.hpp>
#include <map>
using namespace std ;
using namespace boost ;
 
struct function_one // function object
{
  void operator() ( const string& arg ) const 
  { cout << "function_one( " << arg << " )\n" ; }
};
 
void function_two( const string& arg ) // free function
{ cout << "function_two( " << arg << " )\n" ; }
 
struct object
{
  explicit object( int ii = 0 ) : i(0) {}
  int i ;
  void function_three( const string& arg ) // member function
  { cout << "object::function_three( " << arg << " )\n" ; ++i ; }
};
 
int main()
{
  typedef function< void ( const string& ) > function_t ;
  typedef pair< function_t, string > fn_with_arg_t ;
  map< string, fn_with_arg_t > function_map ;
  function_map[ "function object" ] = fn_with_arg_t( function_one(), "one" );
  function_map[ "free function" ] = fn_with_arg_t( function_two, "two" ) ;
  object obj ;
  function_map[ "member function" ] = 
     fn_with_arg_t( bind( &object::function_three, ref(obj), _1 ), "three" );
  string key ;
  while( getline( cin, key ) )
  {
    typedef map< string, fn_with_arg_t >::iterator iterator ;
    iterator ptr = function_map.find(key) ;
    if( ptr != function_map.end() ) ptr->second.first( ptr->second.second ) ;
    else cout << "function not found\n" ;
  }
}
#include <iostream>
#include <boost/function.hpp>
#include <boost/bind.hpp>
#include <map>
using namespace std ;
using namespace boost ;

struct function_one // function object
{
  void operator() ( const string& arg ) const 
  { cout << "function_one( " << arg << " )\n" ; }
};

void function_two( const string& arg ) // free function
{ cout << "function_two( " << arg << " )\n" ; }

struct object
{
  explicit object( int ii = 0 ) : i(0) {}
  int i ;
  void function_three( const string& arg ) // member function
  { cout << "object::function_three( " << arg << " )\n" ; ++i ; }
};

int main()
{
  typedef function< void ( const string& ) > function_t ;
  typedef pair< function_t, string > fn_with_arg_t ;
  map< string, fn_with_arg_t > function_map ;
  function_map[ "function object" ] = fn_with_arg_t( function_one(), "one" );
  function_map[ "free function" ] = fn_with_arg_t( function_two, "two" ) ;
  object obj ;
  function_map[ "member function" ] = 
     fn_with_arg_t( bind( &object::function_three, ref(obj), _1 ), "three" );
  string key ;
  while( getline( cin, key ) )
  {
    typedef map< string, fn_with_arg_t >::iterator iterator ;
    iterator ptr = function_map.find(key) ;
    if( ptr != function_map.end() ) ptr->second.first( ptr->second.second ) ;
    else cout << "function not found\n" ;
  }
}

vijayan121

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