Adapton avoids divide by zero

adapton_avoids_div_by_zero.rs

#[macro_use] 
extern crate adapton;

use adapton::macros::*;
use adapton::engine::*;

fn main() {

    manage::init_dcg();

    let nom  = cell!(42);
    let den  = cell!(2);
        
    // In Rust, cloning is explicit:
    let den2 = den.clone(); // here, we clone the _global reference_ to the cell.
    let den3 = den.clone(); // here, we clone the _global reference_ to the cell, again.

    let div   = thunk![ get!(nom) / get!(den) ];
    let check = thunk![ if get!(den2) == 0 { None } else { Some(get!(div)) } ];
        
    assert_eq!(get!(check), Some(21));
    set(&den3, 0); assert_eq!(get!(check), None);
    set(&den3, 2); assert_eq!(get!(check), Some(21));
}