dxpr 0.2.3

Differentiable expression templates in compile-time, dependency-free, no_std Rust.
Documentation 
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use crate::{expr::Expr, ops, prelude::*};

#[cfg(feature = "std")]
#[test]
fn dbg_var() {
    dbg!(var(&4));
}

#[cfg(feature = "std")]
#[test]
fn dbg_expr() {
    dbg!(Expr(var(&4)));
}

#[cfg(feature = "std")]
#[test]
fn dbg_neg() {
    dbg!(-var(&4));
}

#[cfg(feature = "std")]
#[test]
fn dbg_not() {
    dbg!(!var(&false));
}

#[test]
fn eval_var() {
    assert_eq!(4, *var(&4).eval())
}

#[test]
fn const_eval_var() {
    const VALUE: i32 = *var(&4).eval();
    assert_eq!(4, VALUE);
}

#[test]
fn eval_expr() {
    assert_eq!(4, *Expr(var(&4)).eval())
}

#[test]
fn const_eval_expr() {
    const VALUE: i32 = *Expr(var(&4)).eval();
    assert_eq!(4, VALUE);
}

#[test]
fn neg_var() {
    assert_eq!(-4, (-var(&4)).eval());
}

#[test]
fn const_neg_var() {
    const VALUE: i32 = (-var(&4)).eval();
    assert_eq!(-4, VALUE);
}

#[test]
fn neg_expr() {
    assert_eq!(4, (--var(&4)).eval());
}

#[test]
fn const_neg_expr() {
    const VALUE: i32 = (--var(&4)).eval();
    assert_eq!(4, VALUE);
}

#[test]
fn not_var() {
    assert_eq!(false, (!var(&true)).eval());
}

#[test]
fn not_expr() {
    assert_eq!(true, (!!var(&true)).eval());
}

#[test]
fn eval_twice() {
    let expr: Expr<ops::Neg<ops::Neg<&i32>>> = --var(&4);
    (&expr).eval();
    expr.eval();
}

#[test]
fn add_var() {
    assert_eq!(3, (var(&1) + var(&2)).eval());
}

#[test]
fn add_expr() {
    assert_eq!(15, ((var(&1) + var(&2)) + (var(&4) + var(&8))).eval());
}

#[test]
fn grad_tautological_self_runtime() {
    let x = 1;
    let g = var(&x).grad(&x);
    let v: &i32 = g.eval();
    assert_eq!(1, *v);
}

#[test]
fn grad_tautological_other_runtime() {
    let x = 1;
    let y = 1; // same value!
    let g = var(&x).grad(&y);
    let v: &i32 = g.eval(); // TODO: research and/or ask: why is the type annotation necessary?
    assert_eq!(0, *v);
}

// TODO: investigate the below!

// #[test]
// fn grad_tautological_self_comptime() {
//     const X: i32 = 1;
//     const G: Expr<&i32> = var(&X).grad(&X);
//     const V: &i32 = G.eval();
//     assert_eq!(1, *V);
// }

// #[test]
// fn grad_tautological_other_comptime() {
//     const X: i32 = 1;
//     const Y: i32 = 1; // same value!
//     const G: Expr<&i32> = var(&X).grad(&Y);
//     const V: &i32 = G.eval();
//     assert_eq!(0, *V);
// }

#[test]
fn grad_add_runtime() {
    let a = 4;
    let b = 4;
    let ga = (var(&a) + var(&b)).grad(&a);
    let gb = (var(&a) + var(&b)).grad(&b);
    assert_eq!(1, ga.eval());
    assert_eq!(1, gb.eval());
}

#[test]
fn grad_sub_runtime() {
    let a = 4;
    let b = 4;
    let ga = (var(&a) - var(&b)).grad(&a);
    let gb = (var(&a) - var(&b)).grad(&b);
    assert_eq!(1, ga.eval());
    assert_eq!(-1, gb.eval());
}

// #[test]
// fn grad_mul_runtime() {
//     let a = 37;
//     let b = 42;
//     let expr = var(&a) * var(&b);
//     assert_eq!(42, (&expr).grad(&a).eval());
//     assert_eq!(37, expr.grad(&b).eval());
// }

// TODO:
// #[test]
// fn grad_mul_by_constant() {
//     (var(&2) * var(&1)).eval();
//     (2 * var(&1)).eval();
//     let x = 4;
//     (var(&2) * var(&x)).grad(&x);
// }