Function as a parameter

[Tubs]

Though I *believe* I have declared all the parameters the correct type and everything else, the program still says that the first argument of eval(); is incorrect (I'm just learning how to input a function as a parameter so it is probably just a syntax problem). Any help or tips would be appreciated as always Dev C++

code:

#include <stdio.h> void eval( double f( double farg ), double start, double step, int count); double g (double farg); double h (double farg); int main(int argc, char *argv[]) { double step, i, function, x; int count, start; printf ("What is the starting value of x> "); scanf ("%d", &start); printf ("What is the increment that x increases by> "); scanf ("%lf", &step); printf ("How many values shall be displayed> "); scanf ("%d", &count); printf ("g(x) for x = %d, %.2f, %d\n", start, step, count); printf ("\n"); printf ("x    f(x)\n"); printf ("--   ---\n"); eval(g(x), start, step, count); system ("PAUSE");   return 0; } double g (double farg) { return (5 * pow(farg, 3.0) - 2 * pow(farg, 2.0) + 3); } double h (double farg) { return (pow(farg, 4.0) - 3 * pow(farg, 2.0) - 8); }

[[Gandalf]]

Well, you don't pass a function to another function, you pass the result of the function. So, if you have something returning a double, and you assign a variable, f, that result, then you would just pass f to the function.

Hmm... I was going to give an example, but it seems you don't even have a function eval() in that code

[rizzix]

nay, you can pass functions as parameters.. but he's doing it all wrong..

[[Gandalf]]

Really? Interesting...
Well, I'm pretty sure he just wants to pass the result to the function. Besides, where is this eval()?

[Tubs]

sorry.

code:

void eval( double f( double farg ), double start, double step, int count) { double i; for (i = start; i < count; i + step);     {     printf ("%.1f   %.1f\n", i, (g(i));     } }

[[Gandalf]]

The point remains...

Quote:

Well, you don't pass a function to another function, you pass the result of the function. So, if you have something returning a double, and you assign a variable, f, that result, then you would just pass f to the function.

[Tubs]

Yes, that is what I would do when approaching this problem. BUT!

Quote:

Write a function eval() which takes another function as a parameter and evaluates it over a range of values. The prototype for eval() is:

void eval( double f( double farg ), double start, double step, int count )

Question says otherwise.

[Tubs]

no idea? this is boggling me.

[wtd]

When you declare a pointer to a function, it looks like:

c:

double f( double farg )

This says you have an argument called "f" which takes a "double" argument, and returns a "double".

So when you pass the argument... you just pass the name of the function.

[Tubs]

Have i ever told you how i love you wtd