usaa20/cv3/program.c

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

#define STACK_SIZE 10

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

//push number to the stack

void push(struct stack* stack,float values){
    if(stack->size < 10){
        stack->values[stack->size] = values;
        stack->size += 1;   
    }
    else{
        printf("full stack\n");
        exit(0);

    }
}

//pop number from the stack

float pop(struct stack *stack){
    if(stack->size > 0){
        float value = stack->values[stack->size-1];
        stack->size -= 1;
        return value;
    }
    else{
        printf("not enough operands\n");
        exit(0);
    }
}

void print_stack(struct stack *stack){
    int i;
    int len = stack->size - 1;
    for(i = 0; i < len; i++){
        printf("%0.2f ", stack->values[i]);
    }
    printf("\n");  
}


int main() {
    struct stack mystack;
    memset(&mystack, 0, sizeof(struct stack));
    int i = 0;
    for(i = 0; i < 100; i++){

        char line[10];
        char *x = fgets(line, 10, stdin);
        float r = 0;
        float z = 0;
        
        //if string is not empty
        if(line[1] != 0 && x != NULL){

            //if there is a wrong symbol
            if(!isdigit(line[0]) && line[0] != '+' && line[0] != '*' && line[0] != '/' && line[0] != '-'){
                printf("bad input\n");
                return 0;
            }       

            if(line[0] == '+'){
                r = pop(&mystack) + pop(&mystack);
            }
            else if(line[0] == '-'){
                z = pop(&mystack);   //swap numbers(e.g input "3 4 -"
                r = pop(&mystack) - z;            //output 3 - 4, not 4 - 3)
            }
            else if(line[0] == '*'){
                r = pop(&mystack) * pop(&mystack);
            }
            else if(line[0] == '/'){
                z = pop(&mystack);
                if(z == 0){
                    printf("division by zero\n");
                    return 0;
                }
                else {
                    r = pop(&mystack) / z;
                }
            }
            //if symbol is not operation, than it is number
            //change string to float
            else {
                r = strtof(line,&x);
            } 
            //push result to stack
            push(&mystack,r);
        
            print_stack(&mystack);
        }
        else{
            printf("no input\n");
            return 0;
        }    
    }
      
    return 0;
}