hexga_map_on 0.0.11-beta.53

Define the map_on! macro that can be used to impl a lot of trait quickly using macros.
Documentation 
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

use hexga_map_on::*;

// Similar to Trait From / Into, but those trait suppose no loss when converting, so it is impossible to cast a f32 to a i64 for exemple

/// Might lose some precision.
/// Same semantics as the [`as`](https://practice.course.rs/type-conversions/as.html) keyword: `4f32 as u64`
pub trait CastInto<T>
{
    /// Might lose some precision.
    /// Same semantics as the [`as`](https://practice.course.rs/type-conversions/as.html) keyword: `4f32 as u64`
    fn cast_to(self) -> T;
}

// Double recursive macro :)
macro_rules! impl_cast_to {
    ($itself: ty, $cast_into: ty) => {
        impl CastInto<$cast_into> for $itself
        {
            fn cast_to(self) -> $cast_into { self as _ }
        }
    };

    ($cast_into: ty) => {
        map_on_number!(impl_cast_to, $cast_into);
    };
}
// Do 144 trait impl in a few lines :)
map_on_number!(impl_cast_to);

fn main()
{
    assert_eq!(20.5f32 as i8, 20.5f32.cast_to());

    assert_eq!(4.5 as u32, 4.5.cast_to());
    assert_eq!(4u8 as i64, 4u8.cast_to());
}

/*
// If you also want to support bool
macro_rules! impl_cast_to_bool
{
    ($itself: ty) =>
    {
        impl CastInto<bool> for $itself
        {
            fn cast_to(self) -> bool { self == (0 as $itself) }
        }
    };
}
map_on_number!(impl_cast_to_bool);
impl CastInto<bool> for bool { fn cast_to(self) -> bool { self } }
*/