Format Double as Fraction [closed]

Answer 1

Function for this in a C-variant called LPC follows. Some notes:

1. Addition to input value at beginning is to try to cope with precision issues that otherwise love to wind up telling you that 5 is 4 999999/1000000.
2. The to_int() function truncates to integer.
3. Language has a to_string() that will turn some floats into exponential notation.

---

string strfrac(float frac) {
    int main = to_int(frac + frac / 1000000.0);
    string out = to_string(main);
    float rem = frac - to_float(main);
    string rep;
    if(rem > 0 && (to_int(rep = to_string(rem)) || member(rep, 'e') == Null)) {
        int array primes = ({ 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47 });
        string base;
        int exp;
        int num;
        int div;
        if(sscanf(rep, "%se%d", base, exp) == 2) {
            num = to_int(replace(base, ".", ""));
            div = to_int(pow(10, abs(exp)));
        } else {
            rep = rep[2..];
            num = to_int(rep);
            div = to_int(pow(10, strlen(rep)));
        }
        foreach(int prime : primes) {
            if(prime > num)
                break;
            while((num / prime) * prime == num && (div / prime) * prime == div) {
                num /= prime;
                div /= prime;
            }
        }
        out += " " + num + "/" + div;
    }
    return out;
}