Macro lalrpop_lambda::λ

macro_rules! λ {
    {. $body:ident} => { ... };
    {. $body:expr} => { ... };
    {$($arg:ident)* : $ty:ident . $body:ident} => { ... };
    {$($arg:ident)* . $body:ident} => { ... };
    {$($arg:ident)* : $ty:ident . $body:expr} => { ... };
    {$($arg:ident)* . $body:expr} => { ... };
}

The all-powerful λ

let id = λ!{x.x};

Just a shortcut for abs!.