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

#define STACK_SIZE 10

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

void init(struct stack *s) {
    s->size = 0; 
}

void push_stack(struct stack *s, float value) {
    if (s->size < STACK_SIZE) {
        s->values[s->size] = value;
        s->size++;
    } else {
        printf("full stack\n");
        exit(0); // Exit the program on overflow
    }
}

float pop_stack(struct stack *s) {
    if (s->size > 0) {
        s->size--;
        return s->values[s->size];
    } else {
        printf("no input\n");
        exit(1); // Exit the program on underflow
    }
}

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

int read(struct stack *s) {
    char temp[100];

    // Read a line of input
    if (fgets(temp, sizeof(temp), stdin) == NULL) {
        printf("no input\n");
        return 0; // Error reading input or end of input
    }

    // Check for empty input
    if (strcmp(temp, "\n") == 0) {
        return 1; // Continue to next iteration
    }

    // Check for termination input
    if (strcmp(temp, "end\n") == 0) {
        printf("no input\n"); // Print "no input" upon end
        return 0; 
    }

    float value;
    char extra;
    int scan = sscanf(temp, "%f %c", &value, &extra);

    // If it's a properly formatted number
    if (scan == 1) {
        push_stack(s, value);
        print_stack(s);
    } else if (scan > 1) {
        // If extra characters were found, it's an invalid input like .23.4
        printf("bad input\n");
        exit(0);
    } else {
        switch (temp[0]) {
            case '+':
            case '-':
            case '*':
            case '/': {
                if (s->size < 2) {
                    printf("not enough operands\n");
                    exit(0); // Continue to next iteration
                }

                float b = pop_stack(s);
                float a = pop_stack(s);
                float result;

                switch (temp[0]) {
                    case '+': result = a + b; break;
                    case '-': result = a - b; break;
                    case '*': result = a * b; break;
                    case '/':
                        if (b == 0) {
                            printf("division by zero\n");
                            exit(0);
                        }
                        result = a / b;
                        break;
                }
                push_stack(s, result);
                print_stack(s);
                return 1; // Continue without printing "no input"
            }
            default:
                printf("bad input\n");
                exit(0); // Exit on invalid input
        }
    }

    return 1; // Continue the loop
}


int main() {
    struct stack my_stack;
    init(&my_stack);

    while (1) {
        if (read(&my_stack) == 0) {
            break; 
        }
    }

    return 0;
}