rust_fp_categories/
pure.rs

1use std::rc::Rc;
2
3pub trait Pure {
4    type Elm;
5    type M<U>;
6
7    fn pure(value: Self::Elm) -> Self::M<Self::Elm>;
8
9    fn unit() -> Self::M<()>;
10}
11
12macro_rules! pure_numeric_impl {
13    ($($t:ty)*) => ($(
14        impl Pure for $t {
15          type Elm = $t;
16          type M<U> = U;
17
18          fn pure(value: Self::Elm) -> Self::M<Self::Elm> {
19            value
20          }
21
22          fn unit() -> Self::M<()> {
23            ()
24          }
25        }
26    )*)
27}
28
29pure_numeric_impl! { usize u8 u16 u32 u64 u128 isize i8 i16 i32 i64 i128 f32 f64 }
30
31impl<A> Pure for Rc<A> {
32    type Elm = A;
33    type M<U> = Rc<U>;
34
35    fn pure(value: Self::Elm) -> Self::M<Self::Elm> {
36        Rc::new(value)
37    }
38
39    fn unit() -> Self::M<()> {
40        Rc::new(())
41    }
42}
43
44impl<A> Pure for Box<A> {
45    type Elm = A;
46    type M<U> = Box<U>;
47
48    fn pure(value: Self::Elm) -> Self::M<Self::Elm> {
49        Box::new(value)
50    }
51
52    fn unit() -> Self::M<()> {
53        Box::new(())
54    }
55}
56
57impl<A> Pure for Option<A> {
58    type Elm = A;
59    type M<U> = Option<U>;
60
61    fn pure(value: Self::Elm) -> Self::M<Self::Elm> {
62        Some(value)
63    }
64
65    fn unit() -> Self::M<()> {
66        Some(())
67    }
68}
69
70impl<A, E> Pure for Result<A, E> {
71    type Elm = A;
72    type M<U> = Result<U, E>;
73
74    fn pure(value: Self::Elm) -> Self::M<Self::Elm> {
75        Ok(value)
76    }
77
78    fn unit() -> Self::M<()> {
79        Ok(())
80    }
81}
82
83impl<A> Pure for Vec<A> {
84    type Elm = A;
85    type M<U> = Vec<U>;
86
87    fn pure(value: Self::Elm) -> Self::M<Self::Elm> {
88        vec![value]
89    }
90
91    fn unit() -> Self::M<()> {
92        vec![()]
93    }
94}
rust_fp_categories/pure.rs

rust_fp_categories/
pure.rs
