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// Implement a Calculator class
#import <Foundation/Foundation.h>
@interface Calculator: NSObject
{
 double accumulator;
}
// accumulator methods
-(void) setAccumulator: (double) value;
-(void) clear;
-(double) accumulator;
// arithmetic methods
-(void) add: (double) value;
-(void) subtract: (double) value;
-(void) multiply: (double) value;
-(void) divide: (double) value;
@end
@implementation Calculator
-(void) setAccumulator: (double) value
{
 accumulator = value;
}
-(void) clear
{
 accumulator = 0;
}
-(double) accumulator
{
 return accumulator;
}
-(void) add: (double) value
{
 accumulator += value;
}
-(void) subtract: (double) value
{
 accumulator -= value;
}
-(void) multiply: (double) value
{
 accumulator *= value;
}
-(void) divide: (double) value
{
 accumulator /= value;
}
@end
int main(void)
{
 NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
 
 double value1, value2;
 char operator;
 Calculator *deskCalc = [[Calculator alloc] init];
 
 NSLog (@"Type in your expression.");
 scanf ("%lf %c %lf", &value1, &operator, &value2);
 
 [deskCalc setAccumulator: value1];
 if (operator == '+')
 [deskCalc add: value2];
 else if (operator == '-')
 [deskCalc subtract: value2];
 else if (operator == '*' || operator == 'x')
 [deskCalc multiply: value2];
 else if (operator == '/')
 [deskCalc divide: value2];
 
 NSLog (@"%.2f", [deskCalc accumulator]);
 [deskCalc release];
 
 [pool drain];
 return 0;
}