pipe.rs

// inspired by clojure's ->, pipeline.rs, and s-expressions
macro_rules! pipe_fun {
    // [as t] => it as t
    ([as $typ:ty], $ret:expr) => {
        $ret as $typ;
        };
    // ? => try!(it)
    (?, $ret:expr) => {
        try!($ret)
        };
    // [.a b c] => it.a(b, c)
    ([. $fun:tt $($args:tt)*], $ret:expr) => {
        $ret.$fun($($args),*);
    };
    // [a ; b c] => a(it, b, c)
    ([$fun:tt ; $($rargs:expr)*], $ret:expr) => {
        $fun($ret, $($rargs),*);
    };
    // [a b c ; d] => a(b, c, it, d)
    ([$fun:tt $($largs:expr)+ ; $($rargs:expr)*], $ret:expr) => {
        $fun($($largs),*, $ret, $($rargs),*);
    };
    // [a b c] => a(it, b, c)
    ([$fun:tt $($args:expr)*], $ret:expr) => {
        $fun($ret, $($args),*);
    };
    // (a) => a(it)
    ($fun:tt, $ret:expr) => {
        $fun($ret);
    };
}
macro_rules! pipe {
    ($expr:expr => $($funs:tt)+) => {
        {
            let ret = $expr;
            $( let ret = pipe_fun!($funs, ret);)*
            ret
        }
    };
}