June 2018 Update

Task/Convert-decimal-number-to-rational/Factor/convert-decimal-number-to-rational.factor

@@ -0,0 +1,2 @@
+USE: math.floating-point
+{ 0.9054054 0.518518 0.75 } [ double>ratio ] map [ . ] each

Task/Convert-decimal-number-to-rational/Rust/convert-decimal-number-to-rational.rust

@@ -0,0 +1,58 @@
+extern crate rand;
+extern crate num;
+
+use num::Integer;
+use rand::Rng;
+
+fn decimal_to_rational (mut n : f64) -> [isize;2] {
+    //Based on Farey sequences
+    assert!(n.is_finite());
+    let flag_neg  = n < 0.0;
+    if flag_neg { n = n*(-1.0) }
+    if n < std::f64::MIN_POSITIVE { return [0,1] }
+    if (n - n.round()).abs() < std::f64::EPSILON { return [n.round() as isize, 1] }
+    let mut a : isize = 0;
+    let mut b : isize = 1;
+    let mut c : isize = n.ceil() as isize;
+    let mut d : isize = 1;
+    let aux1 = isize::max_value()/2;
+    while c < aux1  && d < aux1 {
+        let aux2 : f64 = (a as f64 + c as f64)/(b as f64 + d as f64);
+        if (n - aux2).abs() < std::f64::EPSILON { break }
+        if n > aux2 {
+            a = a + c;
+            b = b + d;
+        } else {
+            c = a + c;
+            d = b + d;
+        }
+    }
+    // Make sure that the fraction is irreducible
+    let gcd = (a+c).gcd(&(b+d));
+    if flag_neg { [-(a + c)/gcd, (b + d)/gcd] } else { [(a + c)/gcd, (b + d)/gcd] }
+}
+
+#[test]
+fn test1 () {
+    // Test the function with 1_000_000 random decimal numbers
+    let mut rng = rand::thread_rng();
+    for _i in 1..1_000_000 {
+        let number = rng.gen::<f64>();
+        let result = decimal_to_rational(number);
+        assert!((number - (result[0] as f64)/(result[1] as f64)).abs() < std::f64::EPSILON);
+        assert!(result[0].gcd(&result[1]) == 1);
+    }
+}
+
+fn main () {
+    let mut rng = rand::thread_rng();
+    for _i in 1..10 {
+        let number = rng.gen::<f64>();
+        let result = decimal_to_rational(number);
+        if result[1] == 1 { println!("{} -> {}", number, result[0]) } else { println!("{} ->  {}/{}", number, result[0], result[1]) }
+    }
+    for i in [-0.9054054, 0.518518, -0.75, 0.5185185185185185, -0.9054054054054054, 0.0, 1.0, 2.0].iter() {
+        let result = decimal_to_rational(*i as f64);
+        if result[1] == 1 { println!("{} = {}",*i, result[0]) } else { println!("{} =  {}/{}", *i, result[0], result[1]) }
+    }
+}