gcc error; can't pin down the problem

[rye_]

Hi all,

I'm sure I'll kick myself, but can someone please help me with the error I get for the following code;
http://projecteuler.net/index.php?section=problems&id=9

The code is short enough, and the gcc outputs several and unclear, such that I'm not going to bother posting them.


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

#define LIMIT 300
#define PI 3.14
#define theta = 30, //therefore sin(30) = .5, cos(30) = 1/sqrt(2)

int main(int argc, char * argv[]){

int x_dim;
for (x_dim = 1; x_dim < LIMIT; x_dim++){
double y_dim = x_dim*tan(theta*PI/180);
double hyp = x_dim/cos(theta*PI/180);
double test = x_dim*y_dim*hyp;
if (test == 1000){
printf("answer is %lf\n", test);
break;
}
}

return 0;

}

[mike_g]

Shouldent this:
#define theta = 30, //therefore sin(30) = .5, cos(30) = 1/sqrt(2)
Be:
#define theta 30 //therefore sin(30) = .5, cos(30) = 1/sqrt(2)

Edit: also you dont want be be testing floating point values for equlity.

Edit2: here:
double test = x_dim*y_dim*hyp;
Accoring to whats in the link you posted dosent test want to be:
double test = x_dim+y_dim+hyp;

[hanniph]

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

#define LIMIT 300
#define PI 3.14
//#define theta = 30 //therefore sin(30) = .5, cos(30) = 1/sqrt(2)

int main(int argc, char * argv[]){
int const theta = 30;

int x_dim;
for (x_dim = 1; x_dim < LIMIT; x_dim++){
double y_dim = x_dim*tan(theta*PI/180);
double hyp = x_dim/cos(theta*PI/180);
double test = x_dim*y_dim*hyp;
if (test == 1000){
printf("answer is %lf\n", test);
break;
}
}

return 0;

}

Well, it works if you change define statement.

[rye_]

whoops. thanks guys.
I think sometimes you get too close to the code and can't see obvious mistakes.

Thanks,

again

[DoktorSeven]

In addition to the above, be sure you compile with -lm to specify linking in the math functions.

[rye_]

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

#define LIMIT 400
#define PI 3.14
#define theta 30 //therefore sin(30) = .5, cos(30) = 1/sqrt(2)

int main(int argc, char * argv[]){

int x_dim;
for (x_dim = 1; x_dim < LIMIT; x_dim++){
int y_dim = (int) x_dim*tan(theta*PI/180);
int hyp = (int) x_dim/cos(theta*PI/180);
int test = (int) (x_dim+y_dim+hyp);
//printf("%d\n", test);
if (test == 1000){
printf("answer is %lf\n", x_dim*y_dim*hyp);
break;
}
}

return 0;

}


interesting that it does not locate the answer I'm looking for.
the website doesn't accept the answer 0, for a = 0, b = 500, c = 500
I'll check it symbolically on paper (could be a rounding error I suppose)

[mike_g]

Well I had a poke around with it and got something working. Its not completely accurate, and quite slow. I commented the changes I made. hope that helps :)
#include <stdio.h>
#include <math.h>
#include <stdbool.h>

#define LIMIT 500 //Limit needed to be higher ( finds at around 366)
#define PI 3.14159265
#define THETA 30.0
#define DEG_TO_RAD 0.0174532925 // saves a little extra calculation

int main(int argc, char * argv[])
{
double x_dim; // x_dim needs to be double
for (x_dim = 1; x_dim < LIMIT; x_dim+=0.0001) //Increment needs to be very small to produce a result
{
double y_dim = x_dim*tan(THETA*DEG_TO_RAD);
double hyp = x_dim/cos(THETA*DEG_TO_RAD);
double test = x_dim+y_dim+hyp; // here stuff is added together
if(test > 999.9999 && test < 1000.0001)// Check within range becasue of floating point innacuracy
{
printf("answer has been found\n");
printf("X = %lf\n", x_dim);
printf("Y = %lf\n", y_dim);
printf("H = %lf\n", hyp);
printf("Test result = %lf\n", test);
break;
}
}
getchar();
return 0;
}