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#import "Brain.h"
@interface Brain()
@property (strong, nonatomic) NSMutableArray * arrOperands;
@end
@implementation Brain
-(void) addObject:(double)operand
{
if (!self.arrOperands)
{
self.arrOperands = [[NSMutableArray alloc] init];
}
[self.arrOperands addObject:[NSNumber numberWithDouble:operand]];
}
-(double) performOperation:(NSString *)operation
{
double result = 0;
if (self.arrOperands.count > 1)
{
if([operation isEqualToString:@"+"])
{
result = [self removeLastObject] + [self removeLastObject];
}
if ([operation isEqualToString:@"-"])
{
result = -[self removeLastObject] + [self removeLastObject];
}
if ([operation isEqualToString:@"x"])
{
result = [self removeLastObject] * [self removeLastObject];
}
if ([operation isEqualToString:@"/"] && [[self.arrOperands lastObject] doubleValue] != 0)
{
double tempDivisor = [self removeLastObject];
result = [self removeLastObject] / tempDivisor;
}
}
[self addObject:result];
return result;
}
-(double) removeLastObject
{
NSNumber * lastObject = [self.arrOperands lastObject];
if (self.arrOperands)
{
[self.arrOperands removeLastObject];
}
return [lastObject doubleValue];
}
-(void) clear
{
[self.arrOperands removeAllObjects];
}
@end
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