How Do I Use Function Pointers

Question

0.00/5 (No votes)

See more:

Hi

I have a enum

C++

typedef enum {
    one=1,
    two=2,
    three=3
}mynum;

and i have 4 different functions funtwo .. funfive as below

C++

void funtwo(mynum *c, uint8_t *num )
{
   int x= (int)num+c;
   printf( "num + c = %d \n", x);
}
void funthree(uint8_t *a , uint8_t *b, uint8_t *c )
{
    int x= (int)(*a+*b+*c);
     printf( "a+b+ c = %d \n", x);
}
void funfour(uint8_t *a , uint8_t *b, uint8_t *c, uint32_t *d )
{
   int x= (int)*a+(int)*b+(int)*c+(int)*d;
     printf( "a+b+c+d = %d \n", x);
}
void funfive(uint8_t *a , uint8_t *b, uint8_t *c, uint8_t *d, uint32_t *e)
{
    int x= (int)*a+(int)*b+(int)*c+(int)*d+(int)*e;
     printf( "a+b+c+d = %d \n", x);
}

now if my enum value is 1 then i have to use function 2
if enum is 2 then use fun 3,4 enum is 3 i have to use function 5

How do i do this without if else statement and using function pointers?

Thanks

Posted 29-Sep-15 0:35am

mrajsekar

Updated 29-Sep-15 0:56am

CPallini

v2

Add a Solution

2 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

CPallini · Answer 1 · 2015-09-29T00:59:00

Solution 1

There is no clever way for doing that, since function prototypes are not compatible (you might use a switch, instead of an if chain).

You could rearrange your functions, however, since they basically do the same thing on a different number of parameters, so, a single function like

int sum( int v[], int v_items);

could do the job.

Posted 29-Sep-15 0:59am

CPallini

Comments

Leo Chapiro 29-Sep-15 7:58am

+5, nothing better to do!

CPallini 29-Sep-15 8:03am

Thanks.

Leo Chapiro · Answer 2 · 2015-09-29T01:53:00

Do you mean something like this:

C

typedef void funtwoPtr(mynum *c, uint8_t *num);
typedef void funthreePtr(uint8_t *a , uint8_t *b, uint8_t *c );
/* 
...
...
the same for funfour and five */


funtwoPtr* myFunTwo = &funtwo;
funthreePtr* myFunThree = &funthree;
/* 
...
...
the same for funfour and five */

switch (eNum)
{
   case one:
   {
      myFunTwo(&eNum, &numOne);
      break;
   }
   case two:
   {
      myFunThree(&numOne, &numTwo, &numThree);
      break;
   }
   case three->whatever:
   {
      ...
   }
   default:
   {
      break;
   }
}

/*---------------------------------------------------------------*/