Question

我有后缀计算器，但他不工作，你能帮我吗？我想计算后缀表达式2 sin 2 cos / 5 * 输出为5.000000，但输出正确为0.17... 计算工作！我认为问题在于向堆栈添加表达式。谢谢你的任何建议！

    const char *arrayPostfix[1000];

        //.
        //.
        //.
        //Filling the field
        //field contents:
        //2 <SIN> 2 <COS> </> 5 <*>

        const char *stack[1000];
        int counter = 0;
        int i;
        int numberofElement = 7; // the number of elements - 2 <SIN> 2 <COS> </> 5 <*>
        char myString[100];
        double help;

        for (i = 0; i < numberofElement; i++) {         


            if (arrayPostfix[i][0] != '<') {
                // IS A NUMBER
                stack[counter] = arrayPostfix[i];
                counter++;

            } else {
                // IT ISNT NUMBER
                //// GET LAST OPERATOR - typedef struct 
                // this works
                operator lastOperator;
                int x = 0;

                for (x = 0; x < sizeof(operatory) / sizeof(operator); x++) {
                    if (strcmp(arrayPostfix[i], operatory[x].nazev) == 0) {
                        lastOperator = operatory[x];
                        break;
                    }
                }
                // Operators are ok..

                double n1, n2;

                if (lastOperator.numberofOperators == 2) {// a+b, a-b, a*b, a/b

                    counter--;
                    n1 = atof(stack[counter]);//string to double


                    counter--;
                    n2 = atof(stack[counter]);//string to double


                    help = lastOperator.funkce_dvaOperator(n2, n1); // this works, calculate
                    sprintf(myString, "%f", help); //double to string

                    stack[counter] = myString;
                    counter++;

                } else { // sin(a), cos(a)....

                    counter--;
                    n1 = atof(stack[counter]); //string to double

                    help = lastOperator.funkce_jedenOperator(n1);   // this works, calculate        

                    sprintf(myString, "%f", help); //double to string

                    stack[counter] = myString;
                    counter++;

                }

            }
                    return atof(stack[0]);
        }

步骤进行：

1) add number 2
--------------------------------------------
Index [ 0 ] je : 2
--------------------------------------------


2) calculate sin(2)
--------------------------------------------
Index [ 0 ] je : 0.034899
--------------------------------------------


3) add number 2 - but in stac [0] is fail value..why?
--------------------------------------------
Index [ 0 ] je : 0.034899
Index [ 1 ] je : 0.034899

Answer 1

这是一个非常大的问题：

sprintf(myString, "%f", help); //double to string

stack[counter] = myString;

在此设置指针stack[counter]以指向myString。但是您忘了myString将始终是相同的指针，因此每当您更改myString stack中指向myString的所有条目时因为它是完全相同的字符串而改变了。

后缀计算器不起作用，为什么？ - C

1 个答案: