breakpoints and lots of things

src/stmt.rs

@@ -0,0 +1,80 @@
+use std::fmt::Formatter;
+use std::num::ParseIntError;
+
+#[derive(Debug, Copy, Clone)]
+pub enum Stmt {
+    Inc(usize),
+    Dec(usize),
+    IsZero(usize, usize),
+    Jump(usize),
+    Stop,
+}
+
+pub 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();
+    const DISPLAY_ERR: fn(ParseIntError) -> String = |parse_err| parse_err.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()
+                .map_err(DISPLAY_ERR)?;
+            Stmt::Inc(register)
+        }
+        "DEC" => {
+            let register = iter
+                .next()
+                .ok_or_else(NO_REGISTER)?
+                .parse()
+                .map_err(DISPLAY_ERR)?;
+            Stmt::Dec(register)
+        }
+        "IS_ZERO" => {
+            let register = iter
+                .next()
+                .ok_or_else(NO_REGISTER)?
+                .parse()
+                .map_err(DISPLAY_ERR)?;
+            let line_number = iter
+                .next()
+                .ok_or_else(NO_LINE_NUMBER)?
+                .parse()
+                .map_err(DISPLAY_ERR)?;
+            Stmt::IsZero(register, line_number)
+        }
+        "JUMP" => {
+            let line_number = iter
+                .next()
+                .ok_or_else(NO_LINE_NUMBER)?
+                .parse()
+                .map_err(DISPLAY_ERR)?;
+            Stmt::Jump(line_number)
+        }
+        "STOP" => Stmt::Stop,
+        stmt => return Err(format!("Illegal instruction: '{}'", stmt)),
+    })
+}
+
+impl std::fmt::Display for Stmt {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Stmt::Inc(r) => write!(f, "INC {}", r)?,
+            Stmt::Dec(r) => write!(f, "DEC {}", r)?,
+            Stmt::IsZero(r, line) => write!(f, "IS_ZERO {} {}", r, line)?,
+            Stmt::Jump(r) => write!(f, "JUMP {}", r)?,
+            Stmt::Stop => write!(f, "STOP")?,
+        }
+        Ok(())
+    }
+}