Calculating negative fractions in Objective C
- by Mark Reid
I've been coding my way through Steve Kochan's Programming in Objective-C 2.0 book. I'm up to an exercise in chapter 7, ex 4, in case anyone has the book.
The question posed by the exercise it will the Fraction class written work with negative fractions such as -1/2 + -2/3?
Here's the implementation code in question -
@implementation Fraction
@synthesize numerator, denominator;
-(void) print
{
NSLog(@"%i/%i", numerator, denominator);
}
-(void) setTo: (int) n over: (int) d
{
numerator = n;
denominator = d;
}
-(double) convertToNum
{
if (denominator != 0)
return (double) numerator / denominator;
else
return 1.0;
}
-(Fraction *) add: (Fraction *) f
{
// To add two fractions:
// a/b + c/d = ((a * d) + (b * c)) / (b * d)
// result will store the result of the addition
Fraction *result = [[Fraction alloc] init];
int resultNum, resultDenom;
resultNum = (numerator * f.denominator) + (denominator * f.numerator);
resultDenom = denominator * f.denominator;
[result setTo: resultNum over: resultDenom];
[result reduce];
return result;
}
-(Fraction *) subtract: (Fraction *) f
{
// To subtract two fractions:
// a/b - c/d = ((a * d) - (b * c)) / (b * d)
// result will store the result of the addition
Fraction *result = [[Fraction alloc] init];
int resultNum, resultDenom;
resultNum = numerator * f.denominator - denominator * f.numerator;
resultDenom = denominator * f.denominator;
[result setTo: resultNum over: resultDenom];
[result reduce];
return result;
}
-(Fraction *) multiply: (Fraction *) f
{
// To multiply two fractions
// a/b * c/d = (a*c) / (b*d)
// result will store the result of the addition
Fraction *result = [[Fraction alloc] init];
int resultNum, resultDenom;
resultNum = numerator * f.numerator;
resultDenom = denominator * f.denominator;
[result setTo: resultNum over: resultDenom];
[result reduce];
return result;
}
-(Fraction *) divide: (Fraction *) f
{
// To divide two fractions
// a/b / c/d = (a*d) / (b*c)
// result will store the result of the addition
Fraction *result = [[Fraction alloc] init];
int resultNum, resultDenom;
resultNum = numerator * f.denominator;
resultDenom = denominator * f.numerator;
[result setTo: resultNum over: resultDenom];
[result reduce];
return result;
}
-(void) reduce
{
int u = numerator;
int v = denominator;
int temp;
while (v != 0) {
temp = u % v;
u = v;
v = temp;
}
numerator /= u;
denominator /= u;
}
@end
My question to you is will it work with negative fractions and can you explain how you know? Part of the issue is I don't know how to calculate negative fractions myself so I'm not too sure how to know.
Many thanks.
