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

#define NUMBER '0'
#define MAXLINE 1000
#define MAXVAL 100

int getop(char[]);

void push(double);
double pop(void);
void clear(void);
double peek(void);

// Naïve implementation of remainder operation
double frem(double f1, double f2) {
    return f1 - (f2 * (int)(f1 / f2));
}

/**
 * Reverse polish notation calculator
 */
int main(void) {
    double op2;
    char* line = NULL;
    size_t line_len = 0;
    while (getline(&line, &line_len, stdin) != -1) {
        char* tok = strtok(line, " ");
        do {
            int type = getop(tok);
            switch (type) {
                case NUMBER:
                    push(atof(tok));
                    break;
                case '+':
                    push(pop() + pop());
                    break;
                case '*':
                    push(pop() * pop());
                    break;
                case '-':
                    op2 = pop();
                    push(pop() - op2);
                    break;
                case '/':
                    op2 = pop();
                    if (op2 != 0.0)
                        push(pop() / op2);
                    else
                        printf("error: zero division attempted!\n");
                    break;
                case '%':
                    op2 = pop();
                    if (op2 != 0.0) 
                        push(frem(pop(), op2));
                    else 
                        printf("error: zero division attempted!\n");
                    break;
                case '~':
                    clear();
                    break;
                default:
                    //printf("unknown command %s\n", tok); // Just ignore it?
                    break;
            }
        } while ((tok = strtok(NULL, " ")) != NULL);

        printf("\t%.8g\n", pop());
    }
    free(line); // or, don't bother since we exit the program next...
    
    return 0;
}

int sp; // Stack position
double val[MAXVAL]; // Value stack
void push(double f) {
    if (sp < MAXVAL) {
        val[sp++] = f;
    } else {
        printf("error, stack full\n");
    }
}

double pop(void) {
    if (sp >= 0) {
        return val[--sp];
    } else {
        printf("error, empty stack\n");
        return 0.0;
    }
}

double peek(void) {
    if (sp >= 0) {
        return val[sp-1];
    } else {
        printf("error, empty stack\n");
        return 0.0;
    }   
}

void clear(void) {
    sp = 0;
}

int getop(char s[]) {
    char c = s[0];
    if (!isdigit(c) && c != '.') 
        return c;
    return NUMBER;
}