float x = 4.5;
main()
{
float y,float f();
x*=2.0;
y=f(x);
printf("\n%f%f",x,y);
}
float f (float a)
{
a+=1.3;
x-=4.5;
return(a+x);
}
This program is from the book: Let us C, by Yashwant kanetkar. And the output it says is 4.500000 5.800000. I get error.
//global variable x, can be accessed from anywhere
float x = 4.5;
//inform the compiler, that a function that is defined later, but it exists in the code, and to use it before it's defined, we need to know how it looks like:
float f(float a);
//I need to specify what my main function returns, typically "int"
int main()
{
//local variable for saving the result in:
float y;
//multiply x, with 2, and save the result in x:
x*=2.0;
//run the function:
y=f(x);
//show the result:
printf("\n%f%f",x,y);
//return a value to let the OS know how the program ended (0 is success)
return 0;
}
//define the function
float f (float a)
{
//whatever a is provided, add 1.3 to it before doing anything else
a+=1.3;
//subtract 4.5 from the global variable, before doing anything else:
x-=4.5;
//return the sum of a and x, as the result of this function.
return(a+x);
}
the math here is:
x = 4.5
x = (x * 2) = 9
a = (x = 9) = 9
a = (a + 1.3) = 10.3
x = (x - 4.5) = 4.5
y = a + x = (4.5 + 10.3) = 14.8
Point 1:
Remove float f(); from main(). Declare float f(); outside main(). Thus, it will serve the purpose of forward declaration.
Point 2.
Remove the , and add a ; after float y.
Point 3.
main() should be int main(void).
Note: Consider adding an explicit return statement at the end of main(). Though is is not mandatory, but is considered a good practice.
float y,float f();
Use semicolon after float y
float y;
And float f(); //(wrong prototype). you need to pass argument to this function.
No need to declare function inside main. you can remove float f(); from your main() function.
main not returning any value
Use
int main()
{
//your code
return 0;
}
When you declare f():
float y,float f();
you aren't using a prototype. So when the call to f() is made:
y=f(x);
the float argument x is being promoted by the compiler to a double type.
To solve the problem, declare the function using a full prototype:
float f(float a);
There is no need to declare functions like variables in your main. 2. Also, main() should be int main(). 3. Define/ declare your function before using it.
#include <stdio.h>
float x = 4.5;
float f (float a)
{
a+=1.3;
x-=4.5;
return(a+x);
}
int main(void) {
// your code goes here
float y;
x*=2.0;
y=f(x);
printf("\n%f%f",x,y);
return 0;
}
Ideone link: http://ideone.com/W7V1Qr
