Question

我正在研究计算器的课堂作业。我差不多完成了。

现在，我的计算器可以做2 + 3 + 5x6-3 / 2x6x7-8x9和6 * 9 + 7

但它不能做2 * 4 * 8 .......

任何人都可以告诉我代码有什么问题？这是我在下面的代码：

@implementation CalculatorBrain

- (void)setOperand:(double)aDouble
{
    operand = aDouble;
}


- (double)performOperation:(NSString *)operation
{
    if ([operation isEqual:@"sqrt"]){
        operand = sqrt(operand);
    }
    else if ([@"+/-" isEqual:operation]) {
        operand = - operand;
    }    
    else if ([@"%" isEqual:operation]) {
        operand = operand/ 100;
    }
    else if ([@"1/x" isEqual:operation]) {
        operand = 1/operand;
    }
    else if ([@"C" isEqual:operation]){
        operand = 0;
    }
    else if ([@"AC" isEqual:operation])  {
        operand = 0;
        alwaysFirstDigit = 0;
        digi1 = 0;
        digi2 = 0;

    }else {

        //Assign the first digit to alwaysFirstDigit, and decide the second digit to digi1 or digi2
        if (start == 0){

            alwaysFirstDigit = operand;
            NSLog(@"alwaysFirstDigit = %f", alwaysFirstDigit);

            operationFirst = operation;
            NSLog(@"operationFirst = %@", operationFirst);

            start = 1;

        }else  if (signFlag == 1){
            digi2 = operand;
            NSLog(@"digi2 = %f", digi2);

        }else {
            digi1 = operand;
            NSLog(@"digi1 = %f", digi1);
            }



        // This is an accumulator if first operation is equal to * or /
        if (signFlag == 1) {
        NSLog(@"RUN01 ");


            if ([@"+" isEqual:operationSecond]) 
            {
                digi1 = digi1 + digi2; 
            }
            else if ([@"*" isEqual:operationSecond]) 
            {
                digi1 = digi1 * digi2;
            }
            else if ([@"-" isEqual:operationSecond])
            {
                digi1 = digi1 - digi2;
            }
            else if ([@"/" isEqual:operationSecond]) 
            {
                digi1 = digi1 / digi2;
            }
            digi2 = 0;
            signFlag = 0;
            NSLog(@"This is digi1 in / = %f, %f", digi1, digi2);

        }


        // if operationFirst is = to + or -
        if (([operationFirst isEqual:@"+"]) || ([operationFirst isEqual:@"-"])){  
            NSLog(@"RUN02 ");

        // if operationFirst is = to + or -
            if (([operation isEqual:@"+"]) || ([operation isEqual:@"-"])){

                if ([@"+" isEqual:operationFirst]) 
                {
                    alwaysFirstDigit = alwaysFirstDigit + digi1; 
                }
                else if ([@"-" isEqual:operationFirst]) 
                {
                alwaysFirstDigit = alwaysFirstDigit - digi1;
                }

                operationFirst = operation;  //
                operand = alwaysFirstDigit;  //
            }

            if (([operation isEqual:@"*"]) || ([operation isEqual:@"/"])){
                NSLog(@"RUN03 ");

                signFlag = 1;  //
                operationSecond = operation;  //
                NSLog(@"operationSecond = %@", operationSecond);
            }
        }         


        // it's work
        if (([operationFirst isEqual:@"*"]) || ([operationFirst isEqual:@"/"])){  
            NSLog(@"This is digi1 in *** = %f", alwaysFirstDigit);
            NSLog(@"RUN04 ");

            if (([operation isEqual:@"+"]) || ([operation isEqual:@"-"])){
                NSLog(@"RUN05 ");

                if ([@"*" isEqual:operationFirst]) 
                {
                    alwaysFirstDigit = alwaysFirstDigit * digi1; 
                }
                else if ([@"/" isEqual:operationFirst]) 
                {
                    alwaysFirstDigit = alwaysFirstDigit / digi1;
                }
                operationFirst = operation;  //
                operand = alwaysFirstDigit;  //
            } 

            **// maybe here is the problem !!!!!**
            if (([operation isEqual:@"*"]) || ([operation isEqual:@"/"])){
                NSLog(@"RUN06 ");

                temp1 = digi1;

                operationFirst = operation;  //
                operand = alwaysFirstDigit;  //
            }
        }         


        if([operation isEqual:@"="]){
            NSLog(@"This is temp1 in ***** = %f", temp1);


            if ([@"+" isEqual:operationFirst]) 
            {
                alwaysFirstDigit = alwaysFirstDigit + digi1; 
            }
            else if ([@"*" isEqual:operationFirst]) 
            {
                alwaysFirstDigit = alwaysFirstDigit * digi1;
            }
            else if ([@"-" isEqual:operationFirst])
            {
                alwaysFirstDigit = alwaysFirstDigit - digi1;
            }
            else if ([@"/" isEqual:operationFirst]) 
            {
                alwaysFirstDigit = alwaysFirstDigit / digi1;
            }

                digi1 = 0;
                operand = alwaysFirstDigit;
                operation = @"";
                start = 0;
        }
    }
return operand;
}

@end

Answer 1

在您评论的部分下：

 // if operationFirst is = to + or -

if子句中有一些代码开始：

  if (([operation isEqual:@"*"]) || ([operation isEqual:@"/"])){

此代码永远不会运行，因为它包含在一个if块中：

    if (([operationFirst isEqual:@"+"]) || ([operationFirst isEqual:@"-"])){  
        NSLog(@"RUN02 ");

我不知道这是不是你的问题。您还可能希望将解析器和语法用于您尝试实现的计算器语言。阿尔弗雷德·阿霍（Alfred Aho）和其他人的书“编纂者，原理，技术和工具”称之为“龙书”，因为它在封面上有数十年的龙，是制作和理解语法分析器的传统来源，如桌面计算器（这是它使用的一个例子），这正是你想要编写的代码。除了为桌面计算器提供完美的语法外，它还可以多次增加您对编译器的了解。

计算器（卡在2x2x2操作中）

1 个答案: