Crate monadic

Haskell style block macros "mdo" where monad sources should be expressions of type instances of IntoIterator.

Each monad expression is flat_mapped (into_iter().flat_map( lambda)) with the lambda expression having the monad result variable as argument and the rest as its body, into a lazy FlatMap expression that is also an instance of IntoIterator, and can be collected into any instance of FromIterator.

To use "mdo" (module monad) you must import the traits Bind and Monad defined there.

There are transitive implementation relations for some structures to be instances of IntoIterator:

All iterators implement IntoIterator where into_iter() returns the self iterator structure as documented

Iterator and IntoIterator trait imports are predefined

There are also Reader, Writer and State monads in their respective modules with their own macros.

use num::Integer;
use monadic::{mdo, monad::{Bind, Monad}};

   // available in examples/comprehension.rs

   let xs = mdo!{ 

           x <- 1..7;
           y <- 1..x;
           guard (&y).is_odd() ;
           let z = match x.is_even() { 
                       true => &y + 1,
                       _ => &y - 1,
                   };
           pure (x, z)
            
   }.collect::<Vec<(i32,i32)>>();
    
   println!("result: {:?}", xs); 

   // now with container and item references, available in examples/comprehension2.rs

   let ys = mdo!{ 
    
       &x <- &vec![1,2,3,4];  // with item refs (&x) in the lambda argument position
       guard x.is_odd() ;
       let z = x + 1 ;
       pure (x, z)
        
   }.collect::<Vec<(i32,i32)>>();
    
   println!("result: {:?}", ys); 

Modules

mio
monad	definition of Bind and Monad traits based monadic macro
monoid	Semigroup and Monoid to use with Writer
reader
reader_trans
state	A State monad implementation
util
writer	A Writer monad implementation
writer_trans

Macros

mdo	macro for iterables (IntoIterator) as monads enabling monad comprehensions over iterables
rdrdo	macro for a Reader monad with a boxed (env -> a) function
rdrt_mdo	macro for a ReaderT transformer with a boxed (env -> Monad)
stdo	macro for a State monad with a boxed (s -> (a, s)) function
wrdo	macro for a Writer monad that holds a pair (A, Monoid)
wrt_mdo	macro for a WriterT transformer that holds a (Monad, Monoid) pair