rust-monadic

A macro to write Haskell style monadic code

for IntoIterator (iterables) as monads

Each step monad expression is flat_mapped with the rest into a lazy FlatMap expression which implements IntoIterator with lambdas as move closures capturing the environment and argument.

You can use:

• Some( return_expresion) to return an expression value
• v <- monadic_expression to use the monad result
• _ <- monadic_expression to ignore the monad result
• let z = expression to combine monad results
• guard boolean_expression to filter results

Note: let, within the macro, introduces an expression, not a block.

Example: monadic comprehensions à la Haskell

// examples/comprehension.rs

use monadic::monadic;
use num::Integer;

fn main() {
    let xs = monadic!{ 
    
        x <- 1..7;
        y <- 1..x;
        guard (&y).is_odd() ;
        let z = &y + 1 ;
        Some((x, z)) 
        
    }.collect::<Vec<(i32,i32)>>();
    
    println!("result: {:?}", xs); 
}

$ cargo run --example comprehension

result: [(2, 2), (3, 2), (4, 2), (4, 4), (5, 2), (5, 4), (6, 2), (6, 4), (6, 6)]