Thread: function that takes diff data types as paramter

You need another parameter to indicate what type the pointer is pointing to, since you can't just look at a void* pointer and decide what it's really pointing at.

One way is to use printf/scanf style format strings to encode the type information of the rest of the arguments.

Another way is to use a union of all the possible types, and some kind of identifier to indicate which member of the union is valid.

Code:

struct variant {
  enum { isInt, isFloat } type;
  union {
    int anInt;
    float aFloat;
  } v;
};

This has the advantage of being reasonably type-safe compared to alternatives.

One way would be to tell the function what type you're passing to it:

Code:

#include <stdio.h>

enum { T_FLOAT, T_INT };

int square(void *data, int type)
{
  int result;

  if(type == T_FLOAT)
    result = (*(float *)data) * (*(float *)data);
  else if(type == T_INT)
   result = (*(int *)data) * (*(int *)data);
  else
   result = 0;

  return result;
}

int main(void)
{
  int i = 2;
  float f = 3;

  printf("&#37;d\n", square(&i, T_INT));
  printf("%d\n", square(&f, T_FLOAT));

  return 0;
}

Because (int *) is the data type you need to cast it to. You have a void *, but you want to treat what it points to as an int, so you cast it to an (int *), and then dereference. You can't dereference a void * at all, and this casting of pointer types is necessary. Period. Don't argue it. C will not allow it.

Use a data type bigger than an int. Something like a long long.

Originally Posted by nepdude

hey thanks..not arguing..don't know c that much to do that
this is for the same function that i am making

i am taking input from user and depending upon the type, i either int cast or float cast.
i typecast to int..but suppose the user inputs a value greater than the max limit of int then i get crazy numbers. how can i make sure than if a value greater than INT_MAX than i display an error.

i tried this

Code:

 

int i;
scanf("%d",&i);
if(i > INT_MAX) 
    printf("ERROR");
else
    *(int *)ptr = i;

i did this but still if the value is greater than allowed by int type, it shows some crazy numbers.

You have to compare the floating point value with INT_MAX before you cast it.