Initial data commit

Task/Totient-function/Rust/totient-function.rust

@@ -0,0 +1,27 @@
+use num::integer::gcd;
+
+fn main() {
+    // Compute the totient of the first 25 natural integers
+    println!("N\t phi(n)\t Prime");
+    for n in 1..26 {
+        let phi_n = phi(n);
+        println!("{}\t {}\t {:?}", n, phi_n, phi_n == n - 1);
+    }
+
+    // Compute the number of prime numbers for various steps
+    [1, 100, 1000, 10000, 100000]
+        .windows(2)
+        .scan(0, |acc, tuple| {
+            *acc += (tuple[0]..=tuple[1]).filter(is_prime).count();
+            Some((tuple[1], *acc))
+        })
+        .for_each(|x| println!("Until {}: {} prime numbers", x.0, x.1));
+}
+
+fn is_prime(n: &usize) -> bool {
+    phi(*n) == *n - 1
+}
+
+fn phi(n: usize) -> usize {
+    (1..=n).filter(|&x| gcd(n, x) == 1).count()
+}