From e958ca68997fb33cfcd0951d0f4a96aacc5d47c2 Mon Sep 17 00:00:00 2001
From: Jason Staten <jason.staten@domo.com>
Date: Wed, 30 May 2018 16:21:44 -0600
Subject: [PATCH] It computes!

---
 .gitignore  |   2 +
 Cargo.lock  |   4 ++
 Cargo.toml  |   6 +++
 src/main.rs | 118 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 130 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Cargo.lock
 create mode 100644 Cargo.toml
 create mode 100644 src/main.rs

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..53eaa21
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+/target
+**/*.rs.bk
diff --git a/Cargo.lock b/Cargo.lock
new file mode 100644
index 0000000..bdb4737
--- /dev/null
+++ b/Cargo.lock
@@ -0,0 +1,4 @@
+[[package]]
+name = "rsturing"
+version = "0.1.0"
+
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..42112cd
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "rsturing"
+version = "0.1.0"
+authors = ["Jason Staten <jason.staten@domo.com>"]
+
+[dependencies]
diff --git a/src/main.rs b/src/main.rs
new file mode 100644
index 0000000..d60f10b
--- /dev/null
+++ b/src/main.rs
@@ -0,0 +1,118 @@
+type State = usize;
+
+#[derive(Debug, PartialEq, Clone)]
+enum Cell {
+    Blank,
+    Zero,
+    One,
+}
+
+#[derive(Debug)]
+enum Move {
+    Stay,
+    Left,
+    Right,
+}
+
+struct Transition {
+    start: State,
+    end: State,
+    read: Cell,
+    write: Cell,
+    operation: Move,
+}
+
+struct Machine {
+    initial: State,
+    done: State,
+    transitions: Vec<Transition>,
+}
+
+type Tape = Vec<Cell>;
+
+fn run(machine: Machine, code: Tape) -> Tape {
+    let mut position = 0;
+    let mut state = machine.initial;
+    let mut tape = code.to_vec();
+    tape.resize(10, Cell::Blank);
+
+    while state != machine.done {
+        let transition;
+        {
+            let cell = tape.get(position).unwrap_or(&Cell::Blank);
+            transition = machine
+                .transitions
+                .iter()
+                .find(|t| t.start == state && &t.read == cell)
+                .expect("Missing transition");
+        }
+        state = transition.end;
+        tape[position] = transition.write.clone();
+        position = match transition.operation {
+            Move::Left => position - 1,
+            Move::Right => position + 1,
+            Move::Stay => position,
+        };
+    }
+
+    return tape;
+}
+
+#[test]
+fn test_build() {
+    let machine = Machine {
+        initial: 0,
+        done: 2,
+        transitions: vec![
+            Transition {
+                start: 0,
+                end: 0,
+                read: Cell::Zero,
+                write: Cell::Zero,
+                operation: Move::Right,
+            },
+            Transition {
+                start: 0,
+                end: 0,
+                read: Cell::One,
+                write: Cell::One,
+                operation: Move::Right,
+            },
+            Transition {
+                start: 0,
+                end: 1,
+                read: Cell::Blank,
+                write: Cell::Blank,
+                operation: Move::Left,
+            },
+            Transition {
+                start: 1,
+                end: 1,
+                read: Cell::One,
+                write: Cell::Zero,
+                operation: Move::Left,
+            },
+            Transition {
+                start: 1,
+                end: 2,
+                read: Cell::Zero,
+                write: Cell::One,
+                operation: Move::Stay,
+            },
+            Transition {
+                start: 1,
+                end: 2,
+                read: Cell::Blank,
+                write: Cell::One,
+                operation: Move::Stay,
+            },
+        ],
+    };
+
+    let result = run(machine, vec![Cell::One, Cell::One, Cell::Zero, Cell::One]);
+    println!("{:?}", result);
+
+    let mut expected = vec![Cell::One, Cell::One, Cell::One, Cell::Zero];
+    expected.resize(10, Cell::Blank);
+    assert_eq!(result, expected);
+}