"...redeclared as different kind of symbol"?

Question

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

double integrateF(double low, double high)
{
    double low = 0;
    double high = 20;
    double delta_x=0;
    double x, ans;
    double s = 1/2*exp((-x*x)/2);

    for(x=low;x<=high;x++)
        delta_x = x+delta_x;
    ans = delta_x*s;

    return ans;
}

It says that low and high are "redeclared as different type of symbol" and I don't know what that means. Basically, all I'm doing here (READ: trying) is integrating from low (which I set to 0) to high (20) to find the Riemann sum. The for loop looks kinda trippy too...I'm so lost.

EDIT:

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

double integrateF(double low, double high)
{
    low = 0;
    high = 20;
    double delta_x=0;
    double ans = 0;
    double x;
    double s = 1/2*exp((-x*x)/2);

    for(x=low;x<=high;x++)
    {
        delta_x = x+delta_x;
        ans = ans+(delta_x*s);
    }
    return ans;
}

^That still doesn't work, after the braces and all. It says "undefined reference to 'WinMain@16'"...

Use braces - Otherwise you get caught with you trousers down - this is a good example! — Ed Heal, Oct 20 '13 at 03:55
@CodeBewb:- Make sure you have main() defined. Check my updated answer! — Rahul Tripathi, Oct 20 '13 at 04:42
Just a question, if you are just going to be using variable settings in the function, why are you accepting them as parameters? — Fering, Nov 12 '16 at 16:03
Fix this `1/2`. This is integer division and the result is 0. Use `0.5` directly or `1.0/2` at least. — wilx, Dec 25 '18 at 05:59
You need to have a function named `main` somewhere in your program. — n. m. could be an AI, Dec 25 '18 at 06:07
Or maybe you used the function name as a variable somewhere! — Shirola Ghadirian, Aug 15 '20 at 23:53

score 8 · Answer 1 · answered Oct 20 '13 at 03:57

You are redefinign low and high inside the function which clash with those defined in the parameters.

The for loop is doing

for(x=low;x<=high;x++)
{
   delta_x = x+delta_x;
}

did you mean it to do

for(x=low;x<=high;x++)
{
   delta_x = x+delta_x;
   ans = delta_x*s;
}

However I think you wanted to do ans += delta_x*s;

score 3 · Answer 2 · answered Oct 20 '13 at 04:01

3

lowand high are already passed as parameters of your integrateF method. But they are redeclared again inside the method. Hence the error.

answered Oct 20 '13 at 04:01

Siddhartha Ghosh

2,988
5
18
25

score 1 · Answer 3 · answered Oct 20 '13 at 04:25

1

low and high are already passed as parameters of your integrateF method and they are redeclared again inside the method..

And x is not assigned a value when it is using for the calculation of s..

double x, ans; double s = 1/2*exp((-x*x)/2);

answered Oct 20 '13 at 04:25

Devi K M

63
7

But in the for loop, x starts from "low"...? – CodeNewb Oct 20 '13 at 04:35
but calculation of s is outside the loop na? – Devi K M Oct 20 '13 at 04:56
double s = 1/2*exp((-x*x)/2); // here value of x is not assigned.. for(x=low;x<=high;x++) { delta_x = x+delta_x; ans = ans+(delta_x*s); } – Devi K M Oct 20 '13 at 05:01
How do I do that? I tried setting x as 0 initially but it still doesn't work. I even tried moving the s into the loop. – CodeNewb Oct 20 '13 at 05:14
when i am trying to find the value of exp(-2), i got zero value.. and exp(2) of 7.38.. please print and check the value of s and ans inside loop – Devi K M Oct 20 '13 at 05:45
i call this function and it is compiled .. no error.. but the ans returning is zero.. – Devi K M Oct 20 '13 at 05:50
How did you do it? Ok, I did: double x; double s; for(x=low;x<=high;x++) { delta_x = x+delta_x; s = 1/2*exp((-x*x)/2); ans = ans+(delta_x*s); printf("The integral of the function is equal to %f\n", ans); – CodeNewb Oct 20 '13 at 05:54
It just says "undefined reference to WinMain@16" – CodeNewb Oct 20 '13 at 05:59
from where you call this function? is it from main() ? – Devi K M Oct 20 '13 at 06:06
please check it also http://stackoverflow.com/questions/13459912/undefined-reference-to-winmain16-c-error – Devi K M Oct 20 '13 at 06:06
I'm not sure what you mean by main()? How do I add that to my code? (Sorry...totally clueless) – CodeNewb Oct 20 '13 at 06:15
check it also..it may help u.. http://stackoverflow.com/questions/5259714/undefined-reference-to-winmain16 – Devi K M Oct 20 '13 at 06:17

Rahul Tripathi · Answer 4 · 2013-10-20T04:41:13.303

0

You may want to try like this:-

for(x=low;x<=high;x++)
{                          //Use brackets since you are redefining low and high inside the function
delta_x = x+delta_x;
ans = delta_x*s;
}

or

for(x=low;x<=high;x++)
{                          //Use brackets since you are redefining low and high inside the function
delta_x = x+delta_x;
}

EDIT:-

It says "undefined reference to 'WinMain@16'"

Make sure you have main() or WinMain() defined. Also check that main() is not defined inside of your namespace

edited Oct 20 '13 at 04:41

answered Oct 20 '13 at 03:56

Rahul Tripathi

168,305
31
280
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What do you mean? [Noob here...sorry :( ] The instructions say to *test* it by writing a main function but I should only submit one that contains only the function intergrateF... – CodeNewb Oct 20 '13 at 04:52
I didnt get that very clearly. But I think you are missing the main() function since the error which you are getting is because of that! – Rahul Tripathi Oct 20 '13 at 04:53

score 0 · Answer 5 · answered Dec 25 '18 at 05:57

Another way you can cause this error is by "redefining" your function in a code where that nametag is already used as a variable outside of main function - Like so (psuedo code):

double integrateF = 0;

main(){
 // get vars to integrate ...
}

double integrateF(double, double){
  //do integration
}

You don't even have to call the function inside of main to have an error trying to compile, instead, the compiler cannot make any sense of: double integrateF = 0 = (double, double) { }; outside of main function.

score -1 · Answer 6 · answered Oct 20 '13 at 06:15

when u have declared the data type in the Parameters, you don't have to re-declare them.

instead of

double integrateF(double low, double high)
{
    double low = 0;
    double high = 20;
    .
    .
    .
}

you should do it like this

double integrateF(double low, double high)
{
    low = 0;
    high = 20;
    .
    .
    .
}

"...redeclared as different kind of symbol"?

6 Answers6