输入一个算式（没有空格），遇等号“=”表示输入结束，输出结果。假设计算器只能进行加、减、乘、除运算，运算数和结果都是整数，4种运算符的优先级相同，按“从左到右”的顺序计算。用c写

你可以使用C语言编写一个简单的计算器函数来处理这样的算术表达式。这里是一个基本的示例，我们使用栈来存储操作数和运算符：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

typedef struct {
    int num;
    char op;
} Token;

int is_number(char c) {
    return (isdigit(c) || c == '-');
}

void push(int num, Stack *s) {
    s->top++;
    s->items[s->top] = (Token){num, 'E'};
}

void pop(Stack *s, int *num, char *op) {
    if (s->top > 0) {
        *num = s->items[s->top - 1].num;
        *op = s->items[s->top - 1].op;
        s->top--;
    }
}

double calculate(Stack *s) {
    double result = 0, prev_num = 0;
    char op = ' ';
    while (s->top > 0) {
        Token token = s->items[s->top];
        if (is_number(token.op)) {
            if (op != 'E') {
                result += prev_num * pow(10, token.num);
                prev_num = 0;
            }
            prev_num *= 10;
            prev_num += token.num;
        } else {
            prev_num *= pow(10, token.num);
            switch (op) {
                case '+':
                    result += prev_num;
                    break;
                case '-':
                    result -= prev_num;
                    break;
                case '*':
                    result *= prev_num;
                    break;
                case '/':
                    if (prev_num != 0)
                        result /= prev_num;
                    else
                        printf("Error: Division by zero.\n");
                    break;
            }
            prev_num = 0;
            op = token.op;
        }
        pop(s, &prev_num, &op);
    }
    if (op != 'E')
        result += prev_num;
    return result;
}

int main() {
    Stack s;
    s.top = -1;
    char input[100];
    fgets(input, sizeof(input), stdin);

    for (size_t i = 0; i < strlen(input); i++) {
        if (input[i] == ' ') continue;
        if (isdigit(input[i])) {
            int num = input[i] - '0';
            while (i + 1 < strlen(input) && is_number(input[i + 1])) {
                num = num * 10 + (input[i + 1] - '0');
                i++;
            }
            push(num, &s);
        } else {
            pop(&s, NULL, &input[i]);
            if (s.top == -1) {
                printf("Error: Unexpected operator.\n");
                break;
            }
            char op = input[i];
            if (op == '=') {
                break;
            }
            pop(&s, NULL, &op);
            if (op == '/') {
                if (s.top == -1) {
                    printf("Error: Division without a numerator.\n");
                    break;
                }
                double result = calculate(&s);
                printf("%.0f %c %.0f = %.0f\n", s.items[s.top - 1].num, op, result, calculate(&s));
            } else {
                calculate(&s);
            }
        }
    }
    return 0;
}

这个程序首先读取用户输入的算术表达式，然后逐字符解析，将数字推入栈中，遇到运算符则从栈中弹出最近的操作数进行计算。最后打印出结果。