Stanford CS193P Initial Calculator Code

So I completed the Calculator Code from Stanford CS193P Lecture 2, and got my Calculator to work correctly, only to accidentally delete it from my computer. I then had to re-write the whole code. I also found the RPN Calculator to be a little confusing, and had a hard time getting to work properly at times.

I am therefore posting the initial code for it here. And I’ll post the add-ons as I go through CS193P Assignment 1.

So here is the code…

CalculatorViewController.h

#import <UIKit/UIKit.h>

@interface CalculatorViewController : UIViewController

@property (weak, nonatomic) IBOutlet UILabel *display;

@end

CalculatorViewController.m

#import "CalculatorViewController.h"
#import "CalculatorBrain.h"

@interface CalculatorViewController()
@property (nonatomic) BOOL userIsInTheMiddleOfEnteringANumber;
@property (nonatomic, strong) CalculatorBrain *brain;
@end

@implementation CalculatorViewController

@synthesize display = _display;
@synthesize userIsInTheMiddleOfEnteringANumber = _userIsInTheMiddleOfEnteringANumber;
@synthesize brain = _brain;

- (CalculatorBrain *) brain
{
    if(!_brain) _brain = [[CalculatorBrain alloc] init];
    return _brain;
}

- (IBAction)digitPressed:(UIButton *)sender 
{
    NSString *digit = [sender currentTitle];
    if(self.userIsInTheMiddleOfEnteringANumber) {
     self.display.text = [self.display.text stringByAppendingString:digit];   
    }
    else {
        self.display.text = digit;
        self.userIsInTheMiddleOfEnteringANumber = YES;
    }
    
        
}

- (IBAction)enterPressed 
{
    [self.brain pushOperand:[self.display.text doubleValue]];
    self.userIsInTheMiddleOfEnteringANumber = NO;
}

- (IBAction)operationPressed:(UIButton *)sender 
{   
    if(self.userIsInTheMiddleOfEnteringANumber) [self enterPressed];
    double result = [self.brain performOperation:sender.currentTitle];
    NSString *resultString = [NSString stringWithFormat:@"%g", result];
    self.display.text = resultString;
}


@end

CalculatorBrain.h

#import <Foundation/Foundation.h>

@interface CalculatorBrain : NSObject

- (void)pushOperand:(double)operand;
- (double)performOperation:(NSString *)operation;

@end

CalculatorBrain.m

#import "CalculatorBrain.h"

@interface CalculatorBrain()

@property (nonatomic, strong) NSMutableArray *operandStack;
 
@end

@implementation CalculatorBrain

@synthesize operandStack = _operandStack;

- (NSMutableArray *)operandStack
{
    if(_operandStack == nil) _operandStack = [[NSMutableArray alloc] init];
    return _operandStack;
}

- (void)pushOperand:(double)operand
{
    [self.operandStack addObject:[NSNumber numberWithDouble:operand]];
}

- (double) popOperand
{
    NSNumber *operandObject = [self.operandStack lastObject];
    if(operandObject != nil) [self.operandStack removeLastObject];
    return [operandObject doubleValue];
    
}


- (double)performOperation:(NSString *)operation
{
    double result = 0;
    
    if([operation isEqualToString:@"+"]) {
        result = [self popOperand] + [self popOperand];
    } else if([@"*" isEqualToString:operation]) {
        result = [self popOperand] * [self popOperand];
    } else if ([operation isEqualToString:@"-"]) {
        double subtrahend = [self popOperand];
        result = [self popOperand] - subtrahend;
    } else if ([operation isEqualToString:@"/"]) {
        double divisor = [self popOperand];
        result = [self popOperand] / divisor;
    }
    
    [self pushOperand:result];
    
    return result;
}


@end

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