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

/*
    Appellation: applicative <mod>
    Contrib: FL03 <jo3mccain@icloud.com>
*/
//! # Applicative
//!
//!
use super::functor::Functor;
use super::HKT;

use std::rc::Rc;
use std::sync::Arc;

pub trait Applicative<U>: Functor<U> {
    fn pure_(value: U) -> Self::T
    where
        Self: HKT<U, C = U>;
    fn seq<F>(&self, fs: <Self as HKT<F>>::T) -> <Self as HKT<U>>::T
    where
        F: Fn(&<Self as HKT<U>>::C) -> U,
        Self: HKT<F>;
}

impl<T, U> Applicative<U> for Arc<T> {
    fn pure_(value: U) -> Self::T {
        Arc::new(value)
    }

    fn seq<F>(&self, fs: <Self as HKT<F>>::T) -> Arc<U>
    where
        F: Fn(&T) -> U,
    {
        let v = fs(self);
        Arc::new(v)
    }
}

impl<T, U> Applicative<U> for Box<T> {
    fn pure_(value: U) -> Self::T {
        Box::new(value)
    }

    fn seq<F>(&self, fs: <Self as HKT<F>>::T) -> Box<U>
    where
        F: Fn(&T) -> U,
    {
        let v = fs(self);
        Box::new(v)
    }
}

impl<T, U> Applicative<U> for Option<T> {
    fn pure_(value: U) -> Self::T {
        Some(value)
    }

    fn seq<F>(&self, fs: <Self as HKT<F>>::T) -> Option<U>
    where
        F: Fn(&T) -> U,
    {
        match *self {
            Some(ref value) => match fs {
                Some(f) => Some(f(value)),
                None => None,
            },
            None => None,
        }
    }
}

impl<T, U> Applicative<U> for Rc<T> {
    fn pure_(value: U) -> Self::T {
        Rc::new(value)
    }

    fn seq<F>(&self, fs: <Self as HKT<F>>::T) -> Rc<U>
    where
        F: Fn(&T) -> U,
    {
        let v = fs(self);
        Rc::new(v)
    }
}

impl<T, U> Applicative<U> for Vec<T> {
    fn pure_(value: U) -> Self::T {
        vec![value]
    }

    fn seq<F>(&self, fs: <Self as HKT<F>>::T) -> Vec<U>
    where
        F: Fn(&T) -> U,
    {
        let mut result = Vec::new();
        for (i, f) in fs.into_iter().enumerate() {
            let v = (f)(&self[i]);
            result.push(v)
        }
        return result;
    }
}