Thread: What is wrong with my code?

Can anyone tell me why my C code can't compile:

Code:

#include <stdio.h>
#include <math.h>
#define PI = 3.1415926

int main()
{
int k;
double R, A, V, TR, TA, TV, R_av, A_av, V_av;
for (k = 1; k <= 15; k++) {
R=k/10;
A=4*PI*R*R;
V=A*R/3;
TA=TA+A;
TV=TV+V;
TR=TR+R;
printf ("Sphere ( %d)\t Radius =  %d\t Area =  %d\t Volume =  %d\n", k, R, A, V)
;
R += 0.1;
}


}

This is the error it displays:

iacs5.ucsd.edu% cc hw2v2.c -o hw2
"hw2v2.c", line 11: whitespace between two character assignment operators
"hw2v2.c", line 11: left operand must be modifiable lvalue: op "*="
cc: acomp failed for hw2v2.c

You accidentally put an '=' in your #define PI. Remember, #define's are textual preprocessing substitutions. EVERYTHING to the right of PI will be substituted in for every occurrence of PI in your code.

So this is what the substitution will look like:

Code:

Before:
A=4*PI*R*R;

After:
A=4*= 3.1415926*R*R;

Thanks for the tip arpsmack!

Now I can compile my code but my output is like this:

Sphere ( 1) Radius = 0.0 Area = 0.000 Volume = 0.000
Sphere ( 2) Radius = 0.0 Area = 0.000 Volume = 0.000
Sphere ( 3) Radius = 0.0 Area = 0.000 Volume = 0.000
Sphere ( 4) Radius = 0.0 Area = 0.000 Volume = 0.000
Sphere ( 5) Radius = 0.0 Area = 0.000 Volume = 0.000
Sphere ( 6) Radius = 0.0 Area = 0.000 Volume = 0.000
Sphere ( 7) Radius = 0.0 Area = 0.000 Volume = 0.000
Sphere ( 8) Radius = 0.0 Area = 0.000 Volume = 0.000
Sphere ( 9) Radius = 0.0 Area = 0.000 Volume = 0.000
Sphere ( 10) Radius = 1.0 Area = 12.566 Volume = 4.189
Sphere ( 11) Radius = 1.0 Area = 12.566 Volume = 4.189
Sphere ( 12) Radius = 1.0 Area = 12.566 Volume = 4.189
Sphere ( 13) Radius = 1.0 Area = 12.566 Volume = 4.189
Sphere ( 14) Radius = 1.0 Area = 12.566 Volume = 4.189
Sphere ( 15) Radius = 1.0 Area = 12.566 Volume = 4.189


This is the code:

Code:

#include <stdio.h>
#include <math.h>
#define PI 3.1415926

int main()
{
int k;
double R, A, V, TR, TA, TV, R_av, A_av, V_av;
for (k=1;k<=15;k++) {
R=k/10;
A=4*PI*R*R;
V=A*R/3;

printf ("Sphere ( %d) Radius =  %4.1f Area =  %7.3f Volume =  %7.3f\n",k,R,A,V);
}


}

Why are the radius, area, and volume equations not calculating properly? Thanks again.

Code:

R=k/10;

On the right hand side, 'k' and 10 are both integers, so this is going to result in integer division. Which means, if 'k' is less than 10, R is going to be set to 0 (integer division truncates everything after the decimal point).

Changing the 10 to a 10.0 will make it a double instead of an int.

[edit] heh [/edit]

Originally Posted by arpsmack

Code:

R=k/10;

On the right hand side, 'k' and 10 are both integers, so this is going to result in integer division. Which means, if 'k' is less than 10, R is going to be set to 0 (integer division truncates everything after the decimal point).

Changing the 10 to a 10.0 will make it a double instead of an int.

[edit] heh [/edit]

You have to wake up pretty early in the morning to beat ol' Salem. Or for that matter, you have to be drink a LOT of caffein to beat me and tabstop.