usaa20/cv3/program.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define STACK_SIZE 10

typedef struct {
    float values[STACK_SIZE];
    int size;
} stack;

void stack_print (stack* stack);
void stack_push (stack* stack,float value);
float stack_pop (stack* stack);
void my_exit(int flag, const char* input);

int main(void) {
    stack* p_stack = (stack*) malloc(sizeof(stack));
    memset(p_stack, 0, sizeof(stack));
    while(1) {
        char str[128] = { 0 };
        char* tres = fgets(str, 128, stdin);
        if(tres == NULL || str[0] == 0 || (str[1] == 0 && str[0] == '\n'))
            my_exit(1, "no input");
        str[strlen(str) - 1] = 0;
        // if number
        if(strlen(str) > 1 || (str[0] >= '0' && str[0] <= '9')) {
            my_exit(p_stack->size >= STACK_SIZE, "full stack");
            my_exit(str[0] == '.', "bad input");
            float res = 0.f;
            int dots = 0;
            for(int i = 0; i < strlen(str); i++)
                if(str[i]=='.') dots++;
                else my_exit(str[i] < '0' || str[i] > '9', "bad input");
            res = atof(str);
            stack_push(p_stack, res);
        }
        else {
            my_exit(p_stack->size < 2, "not enough operands");
            float b = stack_pop(p_stack);
            float a = stack_pop(p_stack);
            char op = str[0];
            float res;
            switch (op) {
                case '+':
                    res = a + b;
                    break;
                case '-':
                    res = a - b;
                    break;
                case '*':
                    res = a * b;
                    break;
                case '/':
                    my_exit(b == 0.f, "division by zero");
                    res = a / b;
                    break;
                default:
                    my_exit(1, "bad input");
            }
            stack_push(p_stack, res);
        }
        stack_print(p_stack);
    }
    free(p_stack);
}

void stack_print(stack* st) {
    for(int i = 0; i < st->size; i++)
        printf("%.2f ",st->values[i]);
    printf("\n");
}

void stack_push(stack* st, float push_value) {
    if(st->size < STACK_SIZE)
        st->values[st->size++] = push_value;
}

float stack_pop(stack* st) {
    if(st->size > 0)
        return st->values[--st->size];
}

void my_exit(int flag, const char* input) {
    if (flag) {
        printf("%s\n", input);
        exit(0);
    }
}