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Programming-Idioms

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  • Java

Idiom #348 Convert a decimal value into a fraction

Parse a number, a, into a mathematical fraction, f.

For example, 0.5 is `1/2`, and 3.125 is `3 1/8`.

https://en.wikipedia.org/wiki/Fraction

import static java.lang.Integer.parseInt;
import static java.lang.Math.pow;
import static java.lang.String.valueOf;
String s[] = valueOf(a).split("\\."), f;
int i = parseInt(s[0]), n = parseInt(s[1]),
    d = (int) pow(10, s[1].length()), v;
record GCF() {
    static int of(int a, int b) {
        return b == 0 ? a : of(b, a % b);
    }
}
if ((v = GCF.of(n, d)) != 0) {
    n = n / v;
    d = d / v;
}
if (n == 0) f = valueOf(i);
else if (i != 0) f = "%s %s/%s".formatted(i, n, d);
else f = "%s/%s".formatted(n, d);
let s = a.toString(), f, n, i
i = s.indexOf('.')
if (i == -1) i = s.length - 1
s = s.substring(++i)
n = parseInt(s)
if (!n) f = Math.trunc(a)
else {
    let gcf = (a, b) => !b ? a : gcf(b, a % b),
        d = Math.pow(10, s.length),
        v = gcf(n, d)
    i = Math.trunc(a)
    if (v) {
        n = n / v
        d = d / v
    }
    if (i) f = `${i} ${n}/${d}`
    else f = `${n}/${d}`
}
New implementation...
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reilas 
String s[] = valueOf(a).split("\\."), f;
int i = parseInt(s[0]), n = parseInt(s[1]),
    d = (int) pow(10, s[1].length()), v;
record GCF() {
    static int of(int a, int b) {
        return b == 0 ? a : of(b, a % b);
    }
}
if ((v = GCF.of(n, d)) != 0) {
    n = n / v;
    d = d / v;
}
if (n == 0) f = valueOf(i);
else if (i != 0) f = "%s %s/%s".formatted(i, n, d);
else f = "%s/%s".formatted(n, d);
let s = a.toString(), f, n, i
i = s.indexOf('.')
if (i == -1) i = s.length - 1
s = s.substring(++i)
n = parseInt(s)
if (!n) f = Math.trunc(a)
else {
    let gcf = (a, b) => !b ? a : gcf(b, a % b),
        d = Math.pow(10, s.length),
        v = gcf(n, d)
    i = Math.trunc(a)
    if (v) {
        n = n / v
        d = d / v
    }
    if (i) f = `${i} ${n}/${d}`
    else f = `${n}/${d}`
}
f := FloatToFraction(a);
s = str(a).split('.')
i, n = map(int, s)
d = 10 ** len(str(n))
v = gcd(n, d) or 1
n, d = n // v, d // v
if not n: f = str(i)
elif i: f = f'{i} {n}/{d}'
else: f = f'{n}/{d}'
f = Fraction(a)