Objective C - Quadratic equation solver

Question

So, im making an app that solves quadratic equations. The main interface simply asks the user to input the values of A, B, and C. The problem is, I'm not getting the right answer. Here's the code:

NSString *intStringa = [NSString stringWithFormat:@"%@", a.text];
int aa = [intStringa intValue];
NSString *intStringb = [NSString stringWithFormat:@"%@", b.text];
int bb = [intStringb intValue];
NSString *intStringc = [NSString stringWithFormat:@"%@", c.text];
int cc = [intStringc intValue];
double d = ( -(bb) + ( (bb)^2 - (4*aa*cc) ) ^0,5 ) / (2*aa);
double e = ( -(bb) - ( (bb)^2 - (4*aa*cc) ) ^0.5 ) / (2*aa);
label1.text = [NSString stringWithFormat:@"%lf", d];
label2.text = [NSString stringWithFormat:@"%lf", e];

Any ideas? Thanks!!!

If this is homework please mark it as such (add homework tag). — Rok Jarc, Jan 02 '13 at 17:36
double d = ( -(bb) + ( (bb)^2 - (4*aa*cc) ) ^0,5 ) / (2*aa); apart from ^ another error is 0,5, it should be 0.5 — Anoop Vaidya, Jan 02 '13 at 17:37
thanks, did not notice that. @DanielRuhman: sorry for bad advice — Rok Jarc, Jan 02 '13 at 17:42

score 1 · Answer 1 · answered Jan 02 '13 at 17:35

You can't use ^ for exponentiation in C and related languages (C++, Objective-C, etc) - it's a bitwise XOR operator.

Change:

double d = ( -(bb) + ( (bb)^2 - (4*aa*cc) ) ^0,5 ) / (2*aa);
double e = ( -(bb) - ( (bb)^2 - (4*aa*cc) ) ^0.5 ) / (2*aa);

to:

#include <math.h>

...

double d = - (bb + sqrt(bb * bb - 4 * aa * cc)) / (2 * aa);
double e = - (bb - sqrt(bb * bb - 4 * aa * cc)) / (2 * aa);

Anoop Vaidya · Accepted Answer · 2013-01-03T04:21:19.157

1

Use :

There is no ^ operator for root. use sqrt or pow(base,exp).

double d = ( -bb + sqrt( bb*bb - 4*aa*cc ) ) / (2*aa);
double e = ( -bb - sqrt( bb*bb - 4*aa*cc ) ) / (2*aa);

or,

double d = ( -bb + pow(( bb*bb - 4*aa*cc ), 0.5) ) / (2*aa);
double e = ( -bb - pow(( bb*bb - 4*aa*cc ), 0.5) ) / (2*aa);

edited Jan 03 '13 at 04:21

answered Jan 02 '13 at 17:40

Anoop Vaidya

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Doesn't `sqrt` return a `double`? That would make the numerator `double` and avoid integer division without explicitly making the denominator a `double`. – Ted Hopp Jan 02 '13 at 17:48

score 0 · Answer 3 · answered Jan 02 '13 at 17:37

There is no power ^ operator in C. You have to use pow(b,2) or simply b*b.

And why are you using stringWithFormat? Just use [a.text intValue].

int aa = [a.text intValue];
int bb = [b.text intValue];
int cc = [c.text intValue];
double d = (-bb + sqrt(bb*bb - 4*aa*cc)) / (2.0*aa);
double e = (-bb - sqrt(bb*bb - 4*aa*cc)) / (2.0*aa);
label1.text = [NSString stringWithFormat:@"%lf", d];
label2.text = [NSString stringWithFormat:@"%lf", e];

score 0 · Answer 4 · answered Jan 02 '13 at 17:39

You have a couple of problems: you are using ^ as an exponentiation operator; it is not. You also have a typo in one of the "exponents": 0,5 instead of 0.5. I would write your equations as:

double d = ( -bb + sqrt( bb*bb - 4*aa*cc ) ) / (2*aa);
double e = ( -bb - sqrt( bb*bb - 4*aa*cc ) ) / (2*aa);

Objective C - Quadratic equation solver

4 Answers4