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

#define STACK_SIZE 10

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

int is_operator(const char *str) {
    return (strcmp(str, "+") == 0 ||
            strcmp(str, "-") == 0 ||
            strcmp(str, "*") == 0 ||
            strcmp(str, "/") == 0);
}

void push_stack(struct stack *s, float value) {
    if (s->size >= STACK_SIZE) {
        printf("Chyba: zásobník je plný.\n");
        exit(1);
    }
    s->values[s->size++] = value;
}

void p_stack(struct stack *s) {
    for (int i = 0; i < s->size; i++) {
        (fabsf(s->values[i] - (int)s->values[i]) < 1e-6) ? 
            printf("%d", (int)s->values[i]) : printf("%g", s->values[i]);
        if (i < s->size - 1) printf(" ");
    }
    printf("\n");
}

float remove_stack(struct stack *s) {
    if (s->size <= 0) {
        printf("Chyba: prázdny zásobník.\n");
        exit(1);
    }
    return s->values[--s->size];
}

int main() {
    struct stack mystack = { .size = 0 };
    char input[100];

    while (1) {
        printf("> ");
        fflush(stdout);

        if (!fgets(input, sizeof(input), stdin)) break;

        input[strcspn(input, "\n")] = 0; 

        if (!*input) {
            printf("no input \n");
            break;
        }

        char *endptr;
        float value = strtof(input, &endptr);

        if (endptr != input && *endptr == '\0') {
            push_stack(&mystack, value);
            p_stack(&mystack);
        } else if (is_operator(input)) {
            if (mystack.size < 2) {
                printf("Chyba: nedostatok hodnôt v zásobníku.\n");
                exit(1);
            }

            float b = remove_stack(&mystack);
            float a = remove_stack(&mystack);

            float res = strcmp(input, "+") == 0 ? a + b :
                        strcmp(input, "-") == 0 ? a - b :
                        strcmp(input, "*") == 0 ? a * b :
                        strcmp(input, "/") == 0 ? 
                            (b == 0 ? (printf("Chyba: delenie nulou.\n"), exit(1), 0) : a / b)
                        : 0;

            push_stack(&mystack, res);
            p_stack(&mystack);
        } else {
            printf("Chyba: neplatný vstup.\n");
            exit(1);
        }
    }

    return 0;
}