1 files changed, 44 insertions, 0 deletions
diff --git a/entries/lilylin/fractran/src/core.rs b/entries/lilylin/fractran/src/core.rs
new file mode 100644
index 0000000..26e1a67
--- /dev/null
+++ b/entries/lilylin/fractran/src/core.rs
@@ -0,0 +1,44 @@
+use num_traits::Pow;
+
+pub type FracSize = u16;
+
+#[derive(Debug)]
+pub struct Program {
+    pub fractions: Vec<(FracSize, FracSize)>,
+    pub initial: u64,
+}
+
+impl Program {
+	// http://lomont.org/posts/2017/fractran/
+	// A lesser known Conway FRACTRAN program is FIBONACCIGAME:
+	// `{17/65, 133/34, 17/19, 23/17, 2233/69, 23/29, 31/23, 74/341, 31/37, 41/31, 129/287, 41/43, 13/41, 1/13, 1/3}`
+	// Starting with `78*5^(n-1)`, it halts on `2^Fn` where Fn is the nth [Fibonacci number]
+    pub fn fibonacci(i: u32) -> Program {
+        Program {
+            fractions: vec![
+                (17, 65),
+                (133, 34),
+                (17, 19),
+                (23, 17),
+                (2233, 69),
+                (23, 29),
+                (31, 23),
+                (74, 341),
+                (31, 37),
+                (41, 31),
+                (129, 287),
+                (41, 43),
+                (13, 41),
+                (1, 13),
+                (1, 3),
+            ],
+            initial: 78 * 5u64.pow(i),
+        }
+    }
+}
+
+pub trait FractranEngine<Value>: IntoIterator<Item = Value>
+where
+    Value: From<u64>,
+{
+}