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Programming-Idioms

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

#include <cmath>
#include <iostream>
#include <numeric>
#include <regex>
using namespace std;
string s {to_string(a)}, f;
regex p {"\\."};
sregex_token_iterator r {
    begin(s), end(s), p, -1
};
int i {stoi(*r)}, n {stoi(*++r)},
    d {int(pow(10, r->length()))},
    v {gcd(n, d)};
if (v) {
    n /= v;
    d /= v;
}
if (not n) f = to_string(i);
else {
    f = to_string(n) + '/' + to_string(d);
    if (i) f = to_string(i) + ' ' + f;
}
let s = a.toString(), f,
    [x, y] = s.split('.'),
    i = parseInt(x), n = parseInt(y),
    d = Math.pow(10, y.length),
    gcf = (a, b) => !b ? a : gcf(b, a % b),
    v = gcf(n, d)
if (v) {
    n /= v;
    d /= v;
}
if (!n) f = i.toString()
else {
    f = `${n}/${d}`
    if (i) f = `${i} ${f}`
}
import static java.lang.Integer.parseInt;
import static java.lang.Math.pow;
import static java.lang.String.valueOf;
String s[] = valueOf(a).split("\\."), f;
int i = parseInt(s[0]), n = parseInt(s[1]),
    d = (int) pow(10, s[1].length()), v;
record GCF() {
    static int of(int a, int b) {
        return b == 0 ? a : of(b, a % b);
    }
}
if ((v = GCF.of(n, d)) != 0) {
    n = n / v;
    d = d / v;
}
if (n == 0) f = valueOf(i);
else if (i != 0) f = "%s %s/%s".formatted(i, n, d);
else f = "%s/%s".formatted(n, d);
Fractions
f := FloatToFraction(a);
from math import gcd
s = str(a).split('.')
i, n = map(int, s)
d = 10 ** len(str(n))
v = gcd(n, d) or 1
n, d = n // v, d // v
if not n: f = str(i)
elif i: f = f'{i} {n}/{d}'
else: f = f'{n}/{d}'
from fractions import Fraction
f = Fraction(a)
New implementation...
< > ⌨
reilas 
using namespace std;
string s {to_string(a)}, f;
regex p {"\\."};
sregex_token_iterator r {
    begin(s), end(s), p, -1
};
int i {stoi(*r)}, n {stoi(*++r)},
    d {int(pow(10, r->length()))},
    v {gcd(n, d)};
if (v) {
    n /= v;
    d /= v;
}
if (not n) f = to_string(i);
else {
    f = to_string(n) + '/' + to_string(d);
    if (i) f = to_string(i) + ' ' + f;
}
let s = a.toString(), f,
    [x, y] = s.split('.'),
    i = parseInt(x), n = parseInt(y),
    d = Math.pow(10, y.length),
    gcf = (a, b) => !b ? a : gcf(b, a % b),
    v = gcf(n, d)
if (v) {
    n /= v;
    d /= v;
}
if (!n) f = i.toString()
else {
    f = `${n}/${d}`
    if (i) f = `${i} ${f}`
}
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);
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)