data: add None command

With a None command, it is easy to delete lines without having to recompute indices. This eases some algorithms.

ti-basic-optimizer/src/parse/commands/mod.rs

@@ -20,6 +20,7 @@ use titokens::{Token, Tokens};
 
 #[derive(Clone, Debug)]
 pub enum Command {
+    None,
     ControlFlow(ControlFlow),
     Generic(Generic),
     DelVarChain(DelVarChain),
@@ -85,6 +86,7 @@ impl Reconstruct for Command {
                     .chain(target.reconstruct(config))
                     .collect()
             },
+            Command::None => return vec![],
         };
 
         Expression::strip_closing_parenthesis(&mut line);

ti-basic-optimizer/src/parse/program.rs

@@ -90,6 +90,7 @@ impl Program {
         // to worry about closing strings.
         self.lines
             .iter()
+            .filter(|x|!matches!(x, Command::None))
             .map(|line| line.reconstruct(config))
             .intersperse(vec![Token::OneByte(0x3F)])
             .flatten()
@@ -105,15 +106,15 @@ mod tests {
     #[test]
     fn parses_newlines_correctly_with_strings() {
         let mut tokens = load_test_data("/snippets/parsing/strings/newline-stuff.txt");
-        let mut program = Program::from_tokens(&mut tokens, &test_tokenizer!());
+        let program = Program::from_tokens(&mut tokens, &test_tokenizer!());
 
         assert_eq!(program.lines.len(), 5);
     }
 
     #[test]
     fn skips_blank_lines() {
         let mut tokens = load_test_data("/snippets/parsing/ten-blank-lines.txt");
-        let mut program = Program::from_tokens(&mut tokens, &test_tokenizer!());
+        let program = Program::from_tokens(&mut tokens, &test_tokenizer!());
 
         assert_eq!(program.lines.len(), 0);
     }