inital commit

src/main.rs

@@ -0,0 +1,54 @@
+enum Stmt {
+    Inc(usize),
+    Dec(usize),
+    IsZero(usize, usize),
+    Jump(usize),
+    Stop
+}
+
+fn main() {
+    let filename = match std::env::args().skip(1).next() {
+        Some(name) => name,
+        None => eprintln!("error: no file provided.\nUsage: <filename>"),
+    };
+
+    let program = std::fs::read_to_string(filename).unwrap();
+    let statements = parse(&program);
+}
+
+fn parse(text: &str) -> Result<Vec<Stmt>, String> {
+    text.lines().map(parse_line).collect()
+}
+
+
+fn parse_line(line: &str) -> Result<Stmt, String> {
+    const NO_REGISTER: fn() -> String = || "No register".to_string();
+    const NO_LINE_NUMBER: fn() -> String = || "No line number".to_string();
+    const EMPTY_LINE: fn() -> String = || "Empty line not allowed".to_string();
+
+
+    let mut iter = line.split_ascii_whitespace();
+    let first = iter.next().ok_or_else(EMPTY_LINE)?;
+
+    Ok(match first {
+        "INC" => {
+            let register = iter.next().ok_or_else(NO_REGISTER)?.parse()?;
+            Stmt::Inc(register)
+        }
+        "DEC" => {
+            let register = iter.next().ok_or_else(NO_REGISTER)?.parse()?;
+            Stmt::Dec(register)
+        }
+        "IS_ZERO" => {
+            let register = iter.next().ok_or_else(NO_REGISTER)?.parse()?;
+            let line_number = iter.next().ok_or_else(NO_LINE_NUMBER)?.parse()?;
+            Stmt::IsZero(register, line_number)
+        }
+        "JUMP" => {
+            let line_number = iter.next().ok_or_else(NO_LINE_NUMBER)?.parse()?;
+            Stmt::Jump(line_number)
+        }
+        "STOP" => Stmt::Stop,
+        stmt => return Err(format!("Illegal instruction: '{}'", stmt)),
+    })
+}