Data commit

Task/Padovan-sequence/Rust/padovan-sequence.rust

@@ -0,0 +1,62 @@
+fn padovan_recur() -> impl std::iter::Iterator<Item = usize> {
+    let mut p = vec![1, 1, 1];
+    let mut n = 0;
+    std::iter::from_fn(move || {
+        let pn = if n < 3 { p[n] } else { p[0] + p[1] };
+        p[0] = p[1];
+        p[1] = p[2];
+        p[2] = pn;
+        n += 1;
+        Some(pn)
+    })
+}
+
+fn padovan_floor() -> impl std::iter::Iterator<Item = usize> {
+    const P: f64 = 1.324717957244746025960908854;
+    const S: f64 = 1.0453567932525329623;
+    (0..).map(|x| (P.powf((x - 1) as f64) / S + 0.5).floor() as usize)
+}
+
+fn padovan_lsystem() -> impl std::iter::Iterator<Item = String> {
+    let mut str = String::from("A");
+    std::iter::from_fn(move || {
+        let result = str.clone();
+        let mut next = String::new();
+        for ch in str.chars() {
+            match ch {
+                'A' => next.push('B'),
+                'B' => next.push('C'),
+                _ => next.push_str("AB"),
+            }
+        }
+        str = next;
+        Some(result)
+    })
+}
+
+fn main() {
+    println!("First 20 terms of the Padovan sequence:");
+    for p in padovan_recur().take(20) {
+        print!("{} ", p);
+    }
+    println!();
+
+    println!(
+        "\nRecurrence and floor functions agree for first 64 terms? {}",
+        padovan_recur().take(64).eq(padovan_floor().take(64))
+    );
+
+    println!("\nFirst 10 strings produced from the L-system:");
+    for p in padovan_lsystem().take(10) {
+        print!("{} ", p);
+    }
+    println!();
+
+    println!(
+        "\nLength of first 32 strings produced from the L-system = Padovan sequence? {}",
+        padovan_lsystem()
+            .map(|x| x.len())
+            .take(32)
+            .eq(padovan_recur().take(32))
+    );
+}