Reg Function Pointers

This is a discussion on Reg Function Pointers within the C++ Programming forums, part of the General Programming Boards category; Hi All, I am trying to implement the concept of function pointer in C++. While compiling i got some errors ...

  1. #1
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    Reg Function Pointers

    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.

    attached the code,..


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

    Thanks,
    Sowmi
    Attached Files Attached Files

  2. #2
    Ethernal Noob
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    Expecting some solutions for this code ASAP .
    uh oh.

  3. #3
    and the hat of int overfl Salem's Avatar
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    Try using a proper typedef, by reading this -> http://www.newty.de/fpt/index.html
    As opposed to casting everything to void* and hoping for the best.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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    Quote Originally Posted by indigo0086 View Post
    uh oh.
    That's a great way *not* to get answers =)

  5. #5
    Deathray Engineer MacGyver's Avatar
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    Quote Originally Posted by Desolation View Post
    That's a great way *not* to get answers =)
    Or to get sarcastic replies about deathrays.....

  6. #6
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    Heh, that's a new one...an attempt at code tags in the attached file.
    If I did your homework for you, then you might pass your class without learning how to write a program like this. Then you might graduate and get your degree without learning how to write a program like this. You might become a professional programmer without knowing how to write a program like this. Someday you might work on a project with me without knowing how to write a program like this. Then I would have to do you serious bodily harm. - Jack Klein

  7. #7
    Registered User hk_mp5kpdw's Avatar
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    Here is the attachment as a regular post with code tags (I've fixed the indentation as well):

    command.h
    Code:
    #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
    Code:
    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;
    }
    "Owners of dogs will have noticed that, if you provide them with food and water and shelter and affection, they will think you are god. Whereas owners of cats are compelled to realize that, if you provide them with food and water and shelter and affection, they draw the conclusion that they are gods."
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  8. #8
    Sanity is for the weak! beene's Avatar
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    Well, first of all, post your errors, second, what's with these arrays?
    Code:
    char command[LINELEN];                         
    char parm1[LINELEN];                           
    char parm2[LINELEN];
    What is LINELEN? It isn't declared.

  9. #9
    Frequently Quite Prolix dwks's Avatar
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    Also,
    Code:
    FunctionEntry funArr[MAX_NUM_COMMANDS]=
    {
    	    {"aaa",(FUNCPTR)aaa},
                {"bbb", (FUNCPTR)bbb},
       	    {"ccc",(FUNCPTR)ccc}
    
    };
    enum commandName
    {
    	aaa = 0,
    	bbb
    };
    aaa and bbb are declared after you use them, and ccc is not declared at all.
    Code:
             case Zero :
             case one :
    Use persistent capitalization! It will save you many headaches.
    Code:
    int FunctionEntry :: SearchCommand(char* command)
    {
         /* ... */
         return NULL;
    }
    NULL isn't an int. It's something you put into a pointer. Return 0 or change the return type.
    dwk

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