frappe 0.4.7

Functional Reactive Programming library for Rust
Documentation 
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//! Utilities for lifting functions into signals.

/// Maps a function over the value of signals.
///
/// This converts a function `Fn(A, B, ...) -> R` and the signals `Signal<A>, Signal<B>, ...`
/// into a `Signal<R>` that computes it's value by sampling the input signals and then
/// calling the supplied function.
///
/// # Example
/// ```
/// use frappe::{Sink, Signal, signal_lift};
///
/// let sink = Sink::new();
/// let sig1 = Signal::from_fn(|| 3);
/// let sig2 = sig1.map(|x| x + 24);
///
/// let lifted = signal_lift!(sig1, sig2, sink.stream().hold(0) => |a, b, c| a + b + c);
///
/// sink.send(12);
/// assert_eq!(lifted.sample(), 42);
/// ```
#[macro_export]
macro_rules! signal_lift {
    ($sig:expr => $f:expr) => {
        $crate::Signal::map(&$sig, $f)
    };

    ($($sig:expr),+ => | $($args:pat),+ | $body:expr) => {
        $crate::signal_lift!(@closure $body; $($args)+ ,; $($sig),+)
    };

    ($($sig:expr),+ => $f:expr) => ({
        let f = $f;
        $crate::signal_lift!(@expr f;; $($sig),+)
    });

    (@closure $body:expr ; $($args:pat)* , $($vars:ident)* ;) => {
        $crate::Signal::from_fn(move || {
            let ($($args),*) = ($($crate::Signal::sample(&$vars)),*);
            $body
        })
    };

    (@closure $body:expr ; $($args:pat)* , $($vars:ident)* ; $sig:expr $(,$stail:expr)*) => ({
        let sig = $sig;
        $crate::signal_lift!(@closure $body; $($args)* , $($vars)* sig ; $($stail),*)
    });

    (@expr $f:expr ; $($vars:ident)* ;) => {
        $crate::Signal::from_fn(move || $f($($crate::Signal::sample(&$vars)),*))
    };

    (@expr $f:expr ; $($vars:ident)* ; $sig:expr $(,$stail:expr)*) => ({
        let sig = $sig;
        $crate::signal_lift!(@expr $f ; $($vars)* sig ; $($stail),*)
    });
}

#[cfg(test)]
mod tests {
    use crate::{Signal, Sink};

    #[test]
    fn signal_lift1() {
        let sink = Sink::new();
        let res: Signal<i32> = signal_lift!(sink.stream().hold(0) => |a| a + 1);

        assert_eq!(res.sample(), 1);
        sink.send(12);
        assert_eq!(res.sample(), 13);
    }

    #[test]
    fn signal_lift2_closure() {
        let sink1 = Sink::new();
        let sink2 = Sink::new();
        let res: Signal<String> = signal_lift!(sink1.stream().hold(0), sink2.stream().hold("a") => |a, b| a.to_string() + b);

        assert_eq!(res.sample(), "0a");
        sink1.send(42);
        assert_eq!(res.sample(), "42a");
        sink2.send("xyz");
        assert_eq!(res.sample(), "42xyz");
    }

    #[test]
    fn signal_lift2_expr() {
        fn append<T: ToString>(a: T, b: &str) -> String {
            a.to_string() + b
        }

        let sink1 = Sink::new();
        let sink2 = Sink::new();
        let res: Signal<String> =
            signal_lift!(sink1.stream().hold(0), sink2.stream().hold("a") => append);

        assert_eq!(res.sample(), "0a");
        sink1.send(42);
        assert_eq!(res.sample(), "42a");
        sink2.send("xyz");
        assert_eq!(res.sample(), "42xyz");
    }

    #[test]
    fn signal_lift_pattern() {
        let sink1 = Sink::new();
        let sink2 = Sink::new();
        let sig1 = sink1.stream().hold((0, 1));
        let sig2 = sink2.stream().hold(2);
        let res: Signal<String> =
            signal_lift!(sig1, sig2 => |(a, b), c| a.to_string() + &(b + c).to_string());

        assert_eq!(res.sample(), "03");
        sink1.send((10, 5));
        assert_eq!(res.sample(), "107");
    }
}