math_cell.rs

use std::cell::Cell;
use std::cmp::Ordering;
use std::fmt;

use std::ops::*;

/// A transparent wrapper of [`Cell<T>`](std::cell::Cell) which is identical in every way, except
/// it will implement arithmetic operators as well.
///
/// The purpose of `MathCell` is to be used from [.cell_view()](crate::ArrayBase::cell_view).
/// The `MathCell` derefs to `Cell`, so all the cell's methods are available.
#[repr(transparent)]
#[derive(Default)]
pub struct MathCell<T>(Cell<T>);

impl<T> MathCell<T> {
    /// Create a new cell with the given value
    #[inline(always)]
    pub const fn new(value: T) -> Self { MathCell(Cell::new(value)) }

    /// Return the inner value
    pub fn into_inner(self) -> T { Cell::into_inner(self.0) }

    /// Swap value with another cell
    pub fn swap(&self, other: &Self) {
        Cell::swap(&self.0, &other.0)
    }
}

impl<T> Deref for MathCell<T> {
    type Target = Cell<T>;
    #[inline(always)]
    fn deref(&self) -> &Self::Target { &self.0 }
}

impl<T> DerefMut for MathCell<T> {
    #[inline(always)]
    fn deref_mut(&mut self) -> &mut Self::Target { &mut self.0 }
}

impl<T> Clone for MathCell<T>
    where T: Copy
{
    fn clone(&self) -> Self {
        MathCell::new(self.get())
    }
}

impl<T> PartialEq for MathCell<T>
    where T: Copy + PartialEq
{
    fn eq(&self, rhs: &Self) -> bool {
        self.get() == rhs.get()
    }
}

impl<T> Eq for MathCell<T>
    where T: Copy + Eq
{ }

impl<T> PartialOrd for MathCell<T>
    where T: Copy + PartialOrd
{
    fn partial_cmp(&self, rhs: &Self) -> Option<Ordering> {
        self.get().partial_cmp(&rhs.get())
    }

    fn lt(&self, rhs: &Self) -> bool { self.get().lt(&rhs.get()) }
    fn le(&self, rhs: &Self) -> bool { self.get().le(&rhs.get()) }
    fn gt(&self, rhs: &Self) -> bool { self.get().gt(&rhs.get()) }
    fn ge(&self, rhs: &Self) -> bool { self.get().ge(&rhs.get()) }
}

impl<T> Ord for MathCell<T>
    where T: Copy + Ord
{
    fn cmp(&self, rhs: &Self) -> Ordering {
        self.get().cmp(&rhs.get())
    }
}

impl<T> fmt::Debug for MathCell<T>
    where T: Copy + fmt::Debug
{
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        self.get().fmt(f)
    }
}

macro_rules! impl_math_cell_op {
    ($trt:ident, $op:tt, $mth:ident) => {
    impl<A, B> $trt<B> for MathCell<A>
        where A: $trt<B>
    {
        type Output = MathCell<<A as $trt<B>>::Output>;
        fn $mth(self, other: B) -> MathCell<<A as $trt<B>>::Output> {
            MathCell::new(self.into_inner() $op other)
        }
    }
    };
}

impl_math_cell_op!(Add, +, add);
impl_math_cell_op!(Sub, -, sub);
impl_math_cell_op!(Mul, *, mul);
impl_math_cell_op!(Div, /, div);
impl_math_cell_op!(Rem, %, rem);
impl_math_cell_op!(BitAnd, &, bitand);
impl_math_cell_op!(BitOr, |, bitor);
impl_math_cell_op!(BitXor, ^, bitxor);
impl_math_cell_op!(Shl, <<, shl);
impl_math_cell_op!(Shr, >>, shr);

#[cfg(test)]
mod tests {
    use super::MathCell;
    use crate::arr1;

    #[test]
    fn test_basic() {
        let c = &MathCell::new(0);
        c.set(1);
        assert_eq!(c.get(), 1);
    }

    #[test]
    fn test_math_cell_ops() {
        let s = [1, 2, 3, 4, 5, 6];
        let mut a = arr1(&s[0..3]);
        let b = arr1(&s[3..6]);
        // binary_op
        assert_eq!(a.cell_view() + &b, arr1(&[5, 7, 9]).cell_view());

        // binary_op with scalar
        assert_eq!(a.cell_view() * 2, arr1(&[10, 14, 18]).cell_view());

        // unary_op
        let mut a_v = a.cell_view();
        a_v /= &b;
        assert_eq!(a_v, arr1(&[2, 2, 3]).cell_view());

        // unary_op with scalar
        a_v <<= 1;
        assert_eq!(a_v, arr1(&[4, 4, 6]).cell_view())
    }
}