Chapter 6, Exercise 4

[Shawn]

I worked ahead on this over the weekend. Here's my solution:

Calculator.h

Code: (Objective-C)

#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

Calculator.m

Code: (Objective-C)

#import "Calculator.h"


@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

Ex6-4.m

Code: (Objective-C)

#import "Calculator.h"

int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
	double value;
	char operator;
	Calculator *deskCalc = [[Calculator alloc] init];
	
	do {
		NSLog (@"Type in your expression in the format: number operator");
		scanf ("%lf %c", &value, &operator);
		
		switch (operator) {
			case '+':
				[deskCalc add: value];
				NSLog (@"= %f", [deskCalc accumulator]);
				break;
			case '-':
				[deskCalc subtract: value];
				NSLog (@"= %f", [deskCalc accumulator]);
				break;
			case '*':
				[deskCalc multiply: value];
				NSLog (@"= %f", [deskCalc accumulator]);
				break;
			case '/':
				[deskCalc divide: value];
				NSLog (@"= %f", [deskCalc accumulator]);
				break;
			case 'S':
				[deskCalc setAccumulator: value];
				NSLog (@"= %f", [deskCalc accumulator]);
				break;
			case 'E':
				NSLog (@"End of program.");
				NSLog (@"= %f", [deskCalc accumulator]);
				break;
			default:
				NSLog (@"Unknown operator.");
				break;
		}
	}
	while (operator != 'E');
	
	[deskCalc release];
    [pool drain];
    return 0;
}

Results

2010-03-09 20:13:22.075 Ex6-4[1062:a0f] Type in your expression in the format: number operator
10 S
2010-03-09 20:13:59.321 Ex6-4[1062:a0f] = 10.000000
2010-03-09 20:13:59.322 Ex6-4[1062:a0f] Type in your expression in the format: number operator
2 /
2010-03-09 20:14:06.929 Ex6-4[1062:a0f] = 5.000000
2010-03-09 20:14:06.929 Ex6-4[1062:a0f] Type in your expression in the format: number operator
55 -
2010-03-09 20:14:11.513 Ex6-4[1062:a0f] = -50.000000
2010-03-09 20:14:11.513 Ex6-4[1062:a0f] Type in your expression in the format: number operator
100.25 S
2010-03-09 20:14:18.832 Ex6-4[1062:a0f] = 100.250000
2010-03-09 20:14:18.833 Ex6-4[1062:a0f] Type in your expression in the format: number operator
4 *
2010-03-09 20:14:22.944 Ex6-4[1062:a0f] = 401.000000
2010-03-09 20:14:22.945 Ex6-4[1062:a0f] Type in your expression in the format: number operator
0 E
2010-03-09 20:14:27.936 Ex6-4[1062:a0f] End of program.
2010-03-09 20:14:27.937 Ex6-4[1062:a0f] = 401.000000

[skochan]

Good solution!  Nice and clean.

Cheers,

Steve