macro-example.rs

#[macro_export]                                                                                                
macro_rules! then {                                                                                            
    ($op1:expr => $op2:expr) => {                                                                              
        Monad::bind($op1, Box::new(move |_| {                                                                  
           $op2                                                                                                
        }))                                                                                                    
    }                                                                                                          
}                                                                                                              

// Kind of like `do` notation in haskell.                                                                      
#[macro_export]                                                                                                
macro_rules! perform {                                                                                         
    ($e:expr ; $($rest:tt)+) => ({{                                                                            
        then!($e => perform!($($rest)*));                                                                      
    }});                                                                                                       
    ($b:expr => $a:ident ; $($rest:tt)*) => ({                                                                 
        Monad::bind($b, Box::new(move |$a| {                                                                   
            perform!($($rest)*)                                                                                
        }))                                                                                                    
    });                                                                                                        
    ($e:expr ; ) => { $e; }                                                                                    
}