AbleScript/ablescript
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Slightly better ExecEnv::assign

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A little more idiomatic, avoid some borrow checker clumsiness, add
comments.
This commit is contained in:
Alex Bethel 2021-11-27 11:02:41 -06:00
parent 9727a9b577
commit 711b8e1c03
2 changed files with 28 additions and 15 deletions
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37
ablescript/src/interpret.rs
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@ -11,7 +11,7 @@ use std::{
cell::RefCell,
collections::{HashMap, VecDeque},
io::{stdin, stdout, Read, Write},
mem::swap,
mem::take,
ops::Range,
process::exit,
rc::Rc,
@ -292,28 +292,35 @@ impl ExecEnv {
for index in indices {
let index = self.eval_expr(index)?;
let next_cell;
match &mut *cell.borrow_mut() {
let next_cell = match &mut *cell.borrow_mut() {
Value::Cart(c) => {
// cell is a cart, so we can do simple
// indexing.
if let Some(x) = c.get(&index) {
next_cell = Rc::clone(x);
// cell[index] exists, get a shared
// reference to it.
Rc::clone(x)
} else {
next_cell = Rc::new(RefCell::new(Value::Cart(Default::default())));
// cell[index] does not exist, so we
// insert an empty cart by default
// instead.
let next_cell =
Rc::new(RefCell::new(Value::Cart(Default::default())));
c.insert(index, Rc::clone(&next_cell));
next_cell
}
}
x => {
// Annoying borrow checker dance
// to move *x.
let mut tmp = Value::Nul;
swap(&mut tmp, x);
let mut c = tmp.into_cart();
next_cell = Rc::new(RefCell::new(Value::Cart(Default::default())));
c.insert(index, Rc::clone(&next_cell));
*x = Value::Cart(c);
// cell is not a cart; `take` it, convert
// it into a cart, and write the result
// back into it.
let mut cart = take(x).into_cart();
let next_cell = Rc::new(RefCell::new(Value::Cart(Default::default())));
cart.insert(index, Rc::clone(&next_cell));
*x = Value::Cart(cart);
next_cell
}
}
};
cell = next_cell;
}
cell.replace(value);

6
ablescript/src/variables.rs
View file

@ -60,6 +60,12 @@ pub enum Value {
Cart(Cart),
}
impl Default for Value {
fn default() -> Self {
Self::Nul
}
}
impl Hash for Value {
fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
discriminant(self).hash(state);