Is it possible pass a function as a parameter in C?

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How do you pass a function as a parameter in C?

Is it possible pass a function as a parameter in C? If yes, how?

Duplicate of http://stackoverflow.com/questions/9410/how-do-you-pass-a-function-as-a-parameter-in-c — quamrana, Nov 08 '09 at 18:10

score 9 · Answer 1 · answered Nov 08 '09 at 18:06

9

Use a pointer to function.
Like int (*ptr2_fun)() Receiving function being:
int execute_your_function(int (*fun)())

Here you have some examples

answered Nov 08 '09 at 18:06

Arkaitz Jimenez

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2

check qsort(). It accepts a comparison function. – Alexandru Nov 08 '09 at 18:09

score 9 · Accepted Answer · answered Nov 08 '09 at 18:16

No, you can't pass a 'function' as a parameter. You can, however, pass a pointer to a function instead.

When you reference a function by name without the parentheses for a function invocation, you are referencing a pointer to a function. Thus, for example, we could consider a function that generates a table of values for a mathematical function:

#include <math.h>
#include <stdio.h>

static void generator(double lo, double hi, double inc, double (*function)(double))
{
    double x;
    for (x = lo; x < hi; x += inc)
        printf("x = %6g; f(x) = %6g\n", x, (*function)(x))
}

int main(void)
{
     generator(0.0, 1.0, 0.02, sin);
     generator(0.0, 1.0, 0.02, cos);
     generator(0.0, 1.0, 0.02, sqrt);
     return(0);
}

Here, the functions 'sin()', 'cos()', and 'sqrt()' all have the same prototype schema: function taking a double argument and returning a double value. Note that if I mistakenly wrote:

generator(0.0, 1.0, 0.02, sin());

I would get a bunch of compilation errors - one because 'sin()' expects an argument, and another because 'generator()' expects a pointer to a function and not a double value as the last argument.

(Also note that a good program would at least identify the function it is calculating, and the repeated increments of a double number is not a good idea for accuracy. It is but an example.)

score 6 · Answer 3 · answered Nov 08 '09 at 18:07

6

Use function pointers

answered Nov 08 '09 at 18:07

Naveen

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score 4 · Answer 4 · answered Nov 08 '09 at 18:12

4

Yes. Not a function per se but a pointer to a function instead.

See qsort().

int cmp(const void *a, const void *b) { /* ... */ }
/* ... */
qsort(data, nelems, sizeof *data, cmp); /* pass the function `cmp` to qsort() */

answered Nov 08 '09 at 18:12

pmg

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score 3 · Answer 5 · answered Nov 08 '09 at 18:07

3

Great function pointer tutorial here:

http://www.newty.de/fpt/index.html

answered Nov 08 '09 at 18:07

user204884

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score 3 · Answer 6 · answered Nov 08 '09 at 18:10

Sure, you can use a function pointer.

#include <stdio.h>
typedef void (*bar_callback)(void);

void foo(void)
{
  puts("foo");
}

void bar(bar_callback callback)
{
  puts("bar");
  callback();
}
int main(int argc,char **argv)
{
  bar(foo);
  return 0;
}

Is it possible pass a function as a parameter in C?

6 Answers6