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use crate::Coord;
pub trait Lerp {
fn lerp(self, end: Self, percent: f32) -> Self;
}
#[inline]
pub fn flerp(start: f32, end: f32, percent: f32) -> f32 {
start + ((end - start) * percent)
}
macro_rules! impl_lerp {
($num_type: ty) => {
impl Lerp for $num_type {
#[inline]
fn lerp(self, end: $num_type, percent: f32) -> $num_type {
let start = self as f32;
let end = end as f32;
flerp(start, end, percent).round() as $num_type
}
}
};
}
impl_lerp!(u8);
impl_lerp!(i8);
impl_lerp!(u16);
impl_lerp!(i16);
impl_lerp!(u32);
impl_lerp!(i32);
impl_lerp!(u64);
impl_lerp!(i64);
impl_lerp!(u128);
impl_lerp!(i128);
impl_lerp!(usize);
impl_lerp!(isize);
impl Lerp for Coord {
#[inline]
fn lerp(self, end: Coord, percent: f32) -> Coord {
Coord {
x: self.x.lerp(end.x, percent),
y: self.y.lerp(end.y, percent),
}
}
}
#[cfg(test)]
mod test {
use super::*;
#[test]
fn isize_simple() {
assert_eq!(0_isize.lerp(10, 0.), 0);
assert_eq!(0_isize.lerp(10, 0.5), 5);
assert_eq!(0_isize.lerp(10, 1.), 10);
assert_eq!(0_isize.lerp(10, 0.2), 2);
assert_eq!(5_isize.lerp(10, 0.), 5);
assert_eq!(5_isize.lerp(10, 1.), 10);
assert_eq!(785_isize.lerp(787, 0.), 785);
assert_eq!(785_isize.lerp(787, 0.5), 786);
assert_eq!(785_isize.lerp(787, 1.), 787);
assert_eq!(21_isize.lerp(21, 0.), 21);
assert_eq!(21_isize.lerp(21, 0.5), 21);
assert_eq!(21_isize.lerp(21, 1.), 21);
assert_eq!(10_isize.lerp(1, 1.), 1);
assert_eq!(10_isize.lerp(1, 0.5), 6);
assert_eq!(10_isize.lerp(1, 0.), 10);
assert_eq!((-5_isize).lerp(5, 1.), 5);
assert_eq!((-5_isize).lerp(5, 0.5), 0);
assert_eq!((-5_isize).lerp(5, 0.), -5);
assert_eq!(5_isize.lerp(-5, 1.), -5);
assert_eq!(5_isize.lerp(-5, 0.5), 0);
assert_eq!(5_isize.lerp(-5, 0.), 5);
}
#[test]
fn point_simple() {
let start1 = Coord { x: 0, y: 0 };
let end1 = Coord { x: 10, y: 10 };
let start2 = Coord { x: -1, y: -1 };
let end2 = Coord { x: 1, y: 1 };
let start3 = Coord { x: 1, y: -1 };
let end3 = Coord { x: -1, y: 1 };
assert_eq!(start1.lerp(end1, 0.), Coord { x: 0, y: 0 });
assert_eq!(start1.lerp(end1, 0.5), Coord { x: 5, y: 5 });
assert_eq!(start1.lerp(end1, 1.), Coord { x: 10, y: 10 });
assert_eq!(end1.lerp(start1, 0.), Coord { x: 10, y: 10 });
assert_eq!(end1.lerp(start1, 0.5), Coord { x: 5, y: 5 });
assert_eq!(end1.lerp(start1, 1.), Coord { x: 0, y: 0 });
assert_eq!(start2.lerp(end2, 0.), Coord { x: -1, y: -1 });
assert_eq!(start2.lerp(end2, 0.5), Coord { x: 0, y: 0 });
assert_eq!(start2.lerp(end2, 1.), Coord { x: 1, y: 1 });
assert_eq!(end2.lerp(start2, 0.), Coord { x: 1, y: 1 });
assert_eq!(end2.lerp(start2, 0.5), Coord { x: 0, y: 0 });
assert_eq!(end2.lerp(start2, 1.), Coord { x: -1, y: -1 });
assert_eq!(start3.lerp(end3, 0.), Coord { x: 1, y: -1 });
assert_eq!(start3.lerp(end3, 0.5), Coord { x: 0, y: 0 });
assert_eq!(start3.lerp(end3, 1.), Coord { x: -1, y: 1 });
assert_eq!(end3.lerp(start3, 0.), Coord { x: -1, y: 1 });
assert_eq!(end3.lerp(start3, 0.5), Coord { x: 0, y: 0 });
assert_eq!(end3.lerp(start3, 1.), Coord { x: 1, y: -1 });
assert_eq!(start1.lerp(end1, 2.), Coord { x: 20, y: 20 });
assert_eq!(start1.lerp(end1, -1.), Coord { x: -10, y: -10 });
}
}