messing-around.rs

use std::cell::{RefCell, RefMut};
use std::collections::HashMap;
use std::rc::Rc;
pub use num::{One, Zero};
use std::cmp::PartialEq;

pub use std::ops::{Add, Mul};

pub trait Numeric: Zero + One + Copy + Clone + Mul + Add + PartialEq + std::fmt::Debug {}
// https://stackoverflow.com/questions/42381185/specifying-generic-parameter-to-belong-to-a-small-set-of-types
macro_rules! numeric_impl {
    ($($t: ty),+) => {
        $(
            impl Numeric for $t {}
        )+
    }
}

numeric_impl!(usize, u8, u32, u64, u128, i8, i32, i64, i128, f32, f64);

pub struct Tensor<T: Numeric>(Rc<RefCell<InternalTensor<T>>>);

pub struct InternalTensor<T> where T: Numeric {
    contents: Vec<T>,
    grad:   Vec<T>,
    next:   Vec<Tensor<T>>,
}

fn main() {
    let shared_map: Rc<RefCell<_>> = Rc::new(RefCell::new(HashMap::new()));
    // Create a new block to limit the scope of the dynamic borrow
    {
        let mut map: RefMut<_> = shared_map.borrow_mut();
        map.insert("africa", 92388);
        map.insert("kyoto", 11837);
        map.insert("piccadilly", 11826);
        map.insert("marbles", 38);
    }

    // Note that if we had not let the previous borrow of the cache fall out
    // of scope then the subsequent borrow would cause a dynamic thread panic.
    // This is the major hazard of using `RefCell`.
    let total: i32 = shared_map.borrow().values().sum();
    println!("{total}");
}