floating number sum in c++

Question

I have created this program to convert string to float the program run ok but when I try 1995.1995 it output 1995.2 but it works for other strings like 1 can any explain the reason?

#include <iostream>
#include <iomanip>
using namespace std;
bool isValid(char c) {
    if (c == '.')
        return true;
    if (c >= '0' && c <= '9')
        return true;
    return false;
}
int main()
{
    char input = '0';
    while (isValid(input)) {

        float result = 0;
        bool isFraction = false;
        float divideBy = 1;
        cout << "please enter string to convert : " << endl;
        cin >> input;
        while (true)
        {
            if (input == '.') {

                isFraction = true;
            } 
            else {

                int intInput = input - '0';
                if (isFraction) {
                    divideBy = divideBy * 10;
                    result = result + intInput / divideBy;
                }
                else {
                    result = result * 10 + intInput;
                }
            }
            if (cin.peek() == '\n')
                break;
            cin >> input;
        }
        cout << "Your input is : " << result << endl;
    }
    return 0;
}

You actually get `1995.199462890625`. You need to use `setprecision` to tell `cout` how many decimal digits to display. — NathanOliver, May 14 '20 at 17:55
Floating point numbers have limited precision. They are *not* exact. Recommended reading: [What Every Computer Scientist Should Know About Floating-Point Arithmetic](https://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html). — Jesper Juhl, May 14 '20 at 17:56
Change `cout << "Your input is : " << result << endl;` to `cout << "Your input is : " << setprecision(16) << result << endl;` and you'll the "expected" result. — NathanOliver, May 14 '20 at 18:01
Thanks setprecision worked for me can you write answer so I mark it as answered — Islam Assem, May 14 '20 at 18:03
It's already covered in the duplicate I closed this question to. No need to add another answer that says the same thing. — NathanOliver, May 14 '20 at 18:03

floating number sum in c++

0 Answers0