c - C中的Postfix Notation计算程序，有一些问题

Question

我正在尝试创建一个程序来使用 C 以后缀表示法运行计算，并从 unix 命令行读取值。然而，我对 C 语言还很陌生，并且在让事情正常工作方面遇到了一些麻烦。我得到了 NULL 和段错误的读数，但我不太确定调试在 unix 命令行中是如何工作的，所以我无法告诉你我在哪里得到错误。我将不胜感激任何有关此事的帮助。

#include <stdio.h>
double stack(int argc, char* argv[]);

int main(int argc, char* argv[]) {


    double result;

    result = stack(argc, argv);


    printf("%s\n", result);


}

--

#include <math.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
static double stck[100];
static int top = 0;

/*Push Function*/
static void push( double v){

    stck[top] = v; /* Places the value at the current top position of the stack */
    top++; /* Increases the top position of the stack */
    printf("%s\n", top);

}
/*Pop Function*/
static double pop() {

    double ret;
    ret = stck[top]; /* Stores the value of the top position in the stack to ret */
    top--; /* Decreases the top position of the stack */
    printf("%s\n", top);
    return ret; /* Returns the value of ret */

}

double stack(int argc, char* argv[]){

    double h; /* Placeholder Variable for the result of the mathematic equations during the loop */
    int i;

    for (i = 0; i <= argc - 1; i++) { /* Loops to read in all values, barring the first, for argv */

        if (strcmp(argv[i], "*") == 0) {

            double a = pop();  /* Pulls in the top value of the stack */
            double b = pop();  /* Pulls in the next top value of the stack*/
            h = b*a; /* Performs the multiplication of the two stack values */
            push(h); /* Returns the result to the top of the stack */

        } else if (strcmp(argv[i], "+") == 0) {
            printf("%s\n", "Made it here plus \0");
            double a = pop();  /* Pulls in the top value of the stack */
            double b = pop();  /* Pulls in the next top value of the stack*/
            h = b+a;  /* Performs the multiplication of the two stack values */
            push(h);  /* Returns the result to the top of the stack */

        } else if (strcmp(argv[i], "/") == 0) {

            double a = pop();  /* Pulls in the top value of the stack */
            double b = pop();  /* Pulls in the next top value of the stack*/
            h = b/a; /* Performs the division of the two stack values */
            push(h);  /* Returns the result to the top of the stack */


        } else if (strcmp(argv[i], "^") == 0) {

            double a = pop();  /* Pulls in the top value of the stack */
            double b = pop();  /* Pulls in the next top value of the stack*/
            h = pow(b,a);  /* Raises the number b by the number a power */
            push(h);  /* Returns the result to the top of the stack */


        } else if (strcmp(argv[i], "-") == 0) {

            double a = pop();  /* Pulls in the top value of the stack */
            double b = pop();  /* Pulls in the next top value of the stack*/
            h = b-a;  /* Performs the subtraction of the two stack values */
            push(h);  /* Returns the result to the top of the stack */

        } else {
            printf("%s\n", "Made it here \0");

            double ph;

            ph = (double)atof(argv[i]);
            printf("%s\n", ph);

            push(ph); /* Places the current value of argv[i] on the top of the stack */

        }

    }
    return stck[0]; /* Returns the final result of the calculation to main.c */


}

Answer 1

您的推送和弹出操作需要完全相反。

所以如果推送是

stackarray[index] = v
index++     //increment last

流行一定是

index--     //decrement first
return stackarray[index]

否则，pop 将始终返回最近推送的值之后一个槽中的值。

---

调试使用命令行参数的程序应该与调试任何其他程序没有太大区别。但是您可能需要阅读调试器的文档以了解如何将参数传递给程序。在 gdb 中:

gdb> break main
gdb> run arg1 arg2 arg3 ...

也就是说，将参数添加到 run 行，就好像 run 是程序的名称一样。