Implement point operators with macro

[kaka/rust-sdl-test.git] / src / common.rs

use std::ops::{Add, AddAssign, Sub, SubAssign, Mul, MulAssign, Div, DivAssign, Neg};

pub type Nanoseconds = u64;

#[macro_export]
macro_rules! point {
    ( $x:expr, $y:expr ) => {
        Point2D { x: $x, y: $y }
    };
}

#[derive(Debug, Default, Copy, Clone, PartialEq)]
pub struct Point2D<T> {
    pub x: T,
    pub y: T,
}

impl Point2D<f64> {
    pub fn length(self) -> f64 {
        ((self.x * self.x) + (self.y * self.y)).sqrt()
    }
}

macro_rules! point_op {
    ($op:tt, $trait:ident($fn:ident), $trait_assign:ident($fn_assign:ident), $rhs:ident = $Rhs:ty => $x:expr, $y:expr) => {
        impl<T: $trait<Output = T>> $trait<$Rhs> for Point2D<T> {
            type Output = Self;

            fn $fn(self, $rhs: $Rhs) -> Self {
                Self {
                    x: self.x $op $x,
                    y: self.y $op $y,
                }
            }
        }

        impl<T: $trait<Output = T> + Copy> $trait_assign<$Rhs> for Point2D<T> {
            fn $fn_assign(&mut self, $rhs: $Rhs) {
                *self = Self {
                    x: self.x $op $x,
                    y: self.y $op $y,
                }
            }
        }
    }
}

point_op!(+, Add(add), AddAssign(add_assign), rhs = Point2D<T> => rhs.x, rhs.y);
point_op!(-, Sub(sub), SubAssign(sub_assign), rhs = Point2D<T> => rhs.x, rhs.y);
point_op!(*, Mul(mul), MulAssign(mul_assign), rhs = Point2D<T> => rhs.x, rhs.y);
point_op!(/, Div(div), DivAssign(div_assign), rhs = Point2D<T> => rhs.x, rhs.y);
point_op!(+, Add(add), AddAssign(add_assign), rhs = (T, T) => rhs.0, rhs.1);
point_op!(-, Sub(sub), SubAssign(sub_assign), rhs = (T, T) => rhs.0, rhs.1);
point_op!(*, Mul(mul), MulAssign(mul_assign), rhs = (T, T) => rhs.0, rhs.1);
point_op!(/, Div(div), DivAssign(div_assign), rhs = (T, T) => rhs.0, rhs.1);

////////// multiply point with scalar //////////////////////////////////////////
impl<T: Mul<Output = T> + Copy> Mul<T> for Point2D<T> {
    type Output = Self;

    fn mul(self, rhs: T) -> Self {
	Self {
	    x: self.x * rhs,
	    y: self.y * rhs,
	}
    }
}

impl<T: Mul<Output = T> + Copy> MulAssign<T> for Point2D<T> {
    fn mul_assign(&mut self, rhs: T) {
	*self = Self {
	    x: self.x * rhs,
	    y: self.y * rhs,
	}
    }
}

////////// divide point with scalar ////////////////////////////////////////////
impl<T: Div<Output = T> + Copy> Div<T> for Point2D<T> {
    type Output = Self;

    fn div(self, rhs: T) -> Self {
	Self {
	    x: self.x / rhs,
	    y: self.y / rhs,
	}
    }
}

impl<T: Div<Output = T> + Copy> DivAssign<T> for Point2D<T> {
    fn div_assign(&mut self, rhs: T) {
	*self = Self {
	    x: self.x / rhs,
	    y: self.y / rhs,
	}
    }
}

impl<T: Neg<Output = T>> Neg for Point2D<T> {
    type Output = Self;

    fn neg(self) -> Self {
	Self {
	    x: -self.x,
	    y: -self.y,
	}
    }
}

impl<T> From<(T, T)> for Point2D<T> {
    fn from(item: (T, T)) -> Self {
        Point2D {
            x: item.0,
            y: item.1,
        }
    }
}

#[macro_export]
macro_rules! rect {
    ( $x:expr, $y:expr ) => {
        Rect { x: $x, y: $y }
    };
}

#[derive(Default)]
pub struct Rect<T> {
    pub width: T,
    pub height: T,
}

impl<T: Mul<Output = T> + Copy> Rect<T> {
    #[allow(dead_code)]
    pub fn area(&self) -> T {
        self.width * self.height
    }
}

impl<T> From<(T, T)> for Rect<T> {
    fn from(item: (T, T)) -> Self {
        Rect {
            width: item.0,
            height: item.1,
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn immutable_copy_of_point() {
        let a = point!(0, 0);
        let mut b = a; // Copy
        assert_eq!(a, b); // PartialEq
        b.x = 1;
        assert_ne!(a, b); // PartialEq
    }

    #[test]
    fn add_points() {
        let mut a = point!(1, 0);
        assert_eq!(a + point!(2, 2), point!(3, 2)); // Add
        a += point!(2, 2); // AddAssign
        assert_eq!(a, point!(3, 2));
        assert_eq!(point!(1, 0) + (2, 3), point!(3, 3));
    }

    #[test]
    fn sub_points() {
        let mut a = point!(1, 0);
        assert_eq!(a - point!(2, 2), point!(-1, -2));
        a -= point!(2, 2);
        assert_eq!(a, point!(-1, -2));
        assert_eq!(point!(1, 0) - (2, 3), point!(-1, -3));
    }

    #[test]
    fn mul_points() {
        let mut a = point!(1, 2);
        assert_eq!(a * 2, point!(2, 4));
        assert_eq!(a * point!(2, 3), point!(2, 6));
        a *= 2;
        assert_eq!(a, point!(2, 4));
        a *= point!(3, 1);
        assert_eq!(a, point!(6, 4));
        assert_eq!(point!(1, 0) * (2, 3), point!(2, 0));
    }

    #[test]
    fn div_points() {
        let mut a = point!(4, 8);
        assert_eq!(a / 2, point!(2, 4));
        assert_eq!(a / point!(2, 4), point!(2, 2));
        a /= 2;
        assert_eq!(a, point!(2, 4));
        a /= point!(2, 4);
        assert_eq!(a, point!(1, 1));
        assert_eq!(point!(6, 3) / (2, 3), point!(3, 1));
    }

    #[test]
    fn neg_point() {
        assert_eq!(point!(1, 1), -point!(-1, -1));
    }

    #[test]
    fn area_for_rect_of_multipliable_type() {
        let r: Rect<_> = (30, 20).into(); // the Into trait uses the From trait
        assert_eq!(r.area(), 30 * 20);
        // let a = Rect::from(("a".to_string(), "b".to_string())).area(); // this doesn't work, because area() is not implemented for String
    }
}