1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117

//! 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");
    }
}