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

#define STACK_SIZE 10

struct stack{                  //definition of STACK struct
    float values[STACK_SIZE];
    int size;
};

//function which prints contents of stack
void print_stack(struct stack* stack); 

//function to append element into stack
void push_stack(struct stack* stack, float value);

//function to delete last element of stack
float pop_stack(struct stack* stack);

//function to sum last 2 operands from stack
void sum(struct stack* stack);

//function to substract last 2 operands from stack
void substract(struct stack* stack);

//function to multiply last 2 operands from stack
void multip(struct stack* stack);

//function to divide last 2 operands from stack
void divis(struct stack* stack, float a);


int main(){
    
    char char_value[STACK_SIZE];      //definition of input array

    memset(&char_value,0,STACK_SIZE); //inicialization of input array
    
    float float_value;                //variable to which we convert number from input array (char_value[])
    char* ptr;                        //return pointer of fgets
    struct stack myStack;             //struct myStach of type stack
    memset(&myStack,0,sizeof(struct stack)); //initialization of myStruct structure
    while(1){
        if(myStack.size == 10){         //condition to break the cycle if we have full stack
            puts("full stack");
            break;
        }

        //load input into char_value
        ptr = fgets(char_value, STACK_SIZE-1, stdin);
        if(ptr != NULL){                //check if it run ok
            if(char_value[0] == '\n'){  //if first char is \n, break the cycle, its the end
                puts("no input");
                break;
            }
            
            //sum
            if(char_value[0] == '+'){
                    if(myStack.size > 1){
                        sum(&myStack);
                    }else{puts("not enough operands"); break;}
            }
            
            //substraction
            else if(char_value[0] == '-'){
                    if(myStack.size > 1){
                        substract(&myStack);
                    }else{puts("not enough operands"); break;}
            }
            
            //multiplication
            else if(char_value[0] == '*'){
                    if(myStack.size > 1){
                        multip(&myStack);
                    }else{puts("not enough operands"); break;}
            }
            
            //division
            else if(char_value[0] == '/'){
                    if(myStack.size > 1){
                        float a = pop_stack(&myStack);
                        if(a == 0){
                            printf("division by zero\n");
                            break;
                        }else{
                            divis(&myStack, a);
                        }
                    }else{puts("not enough operands"); break;}
            } 
            
            //if its a number
            else if(isdigit(char_value[0]) != 0 ){
                    float_value = strtof(char_value, NULL);
                    push_stack(&myStack,float_value);
                    print_stack(&myStack);
                    printf("\n");
                    continue;
            } else {
                puts("bad input"); //if its not digit nor symbol of operation, break cycle, bad input 
                break;
            }

        //if theres no further input
        } else { 
            puts("no input");
            break;
        }
    } 


    return 0;
}

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

void push_stack(struct stack* stack, float value){
    //assert(stack->size < STACK_SIZE);
    stack->values[stack->size] = value;
    stack->size += 1;
}

float pop_stack(struct stack* stack){
    //assert(stack->size > 0);
    float value = stack->values[stack->size-1];
    stack->size -= 1;
    return value;
}

void sum(struct stack* stack){
    float a = pop_stack(stack);
    float b = pop_stack(stack);                    
    float c = a+b;
    push_stack(stack, c);
    print_stack(stack);
    printf("\n");
}

void substract(struct stack* stack){
    float a = pop_stack(stack);
    float b = pop_stack(stack);                    
    float c = b-a;
    push_stack(stack, c);
    print_stack(stack);
    printf("\n");
}

void multip(struct stack* stack){
    float a = pop_stack(stack);
    float b = pop_stack(stack);                    
    float c = a*b;
    push_stack(stack, c);
    print_stack(stack);
    printf("\n");
}



void divis(struct stack* stack, float a){ 
        float b = pop_stack(stack);                    
        float c = b/a;
        push_stack(stack, c);
        print_stack(stack);
        printf("\n");
}