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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?
- 2Duplicate of stackoverflow.com/questions/9410/…quamrana– quamrana2009-11-08 18:10:09 +00:00Commented Nov 8, 2009 at 18:10
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6 Answers
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.)
answered Nov 8, 2009 at 18:16
Jonathan Leffler
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Use a pointer to function.
Like int (*ptr2_fun)() Receiving function being:
int execute_your_function(int (*fun)())
Here you have some examples
1 Comment
Alexandru
check qsort(). It accepts a comparison function.
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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() */ 
Comments
Great function pointer tutorial here:
Comments
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; } 