Macro undo::merge

macro_rules! merge {
    ($cmd1:expr, $cmd2:expr) => { ... };
    ($cmd1:expr, $cmd2:expr, $($tail:expr),+) => { ... };
}

Macro for merging commands.

Examples

#[derive(Debug)]
struct Add(char);

impl Command<String> for Add {
    fn apply(&mut self, s: &mut String) -> Result<(), Box<dyn Error + Send + Sync>> {
        s.push(self.0);
        Ok(())
    }

    fn undo(&mut self, s: &mut String) -> Result<(), Box<dyn Error + Send + Sync>> {
        self.0 = s.pop().ok_or("`s` is empty")?;
        Ok(())
    }
}

fn main() -> Result<(), Box<dyn Error>> {
    let mut record = Record::default();

    let cmd = merge![Add('a'), Add('b'), Add('c')];
    record.apply(cmd)?;
    assert_eq!(record.as_receiver(), "abc");
    record.undo().unwrap()?;
    assert_eq!(record.as_receiver(), "");
    record.redo().unwrap()?;
    assert_eq!(record.as_receiver(), "abc");

    Ok(())
}