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//! These tests use a simple constant expression tree to demonstrate the use of the `gen_reduce` crate.
use tree_morph::prelude::*;
use uniplate::Uniplate;
#[derive(Debug, Clone, PartialEq, Eq, Uniplate)]
#[uniplate()]
enum Expr {
Add(Box<Expr>, Box<Expr>),
Mul(Box<Expr>, Box<Expr>),
Val(i32),
}
fn rule_eval_add(_: &mut Commands<Expr, Meta>, expr: &Expr, _: &Meta) -> Option<Expr> {
match expr {
Expr::Add(a, b) => match (a.as_ref(), b.as_ref()) {
(Expr::Val(x), Expr::Val(y)) => Some(Expr::Val(x + y)),
_ => None,
},
fn rule_eval_mul(_: &mut Commands<Expr, Meta>, expr: &Expr, _: &Meta) -> Option<Expr> {
Expr::Mul(a, b) => match (a.as_ref(), b.as_ref()) {
(Expr::Val(x), Expr::Val(y)) => Some(Expr::Val(x * y)),
#[derive(Clone)]
enum MyRule {
EvalAdd,
EvalMul,
impl Rule<Expr, Meta> for MyRule {
fn apply(&self, cmd: &mut Commands<Expr, Meta>, expr: &Expr, meta: &Meta) -> Option<Expr> {
cmd.mut_meta(Box::new(|m: &mut Meta| m.num_applications += 1)); // Only applied if successful
match self {
MyRule::EvalAdd => rule_eval_add(cmd, expr, meta),
MyRule::EvalMul => rule_eval_mul(cmd, expr, meta),
#[derive(Debug)]
struct Meta {
num_applications: u32,
#[test]
fn single_var() {
let expr = Expr::Val(42);
let meta = Meta {
num_applications: 0,
};
let mut engine = EngineBuilder::new()
.add_rule_group(vec![MyRule::EvalAdd, MyRule::EvalMul])
.build();
let (expr, meta) = engine.morph(expr, meta);
assert_eq!(expr, Expr::Val(42));
assert_eq!(meta.num_applications, 0);
fn add_zero() {
let expr = Expr::Add(Box::new(Expr::Val(0)), Box::new(Expr::Val(42)));
assert_eq!(meta.num_applications, 1);
fn mul_one() {
let expr = Expr::Mul(Box::new(Expr::Val(1)), Box::new(Expr::Val(42)));
fn eval_add() {
let expr = Expr::Add(Box::new(Expr::Val(1)), Box::new(Expr::Val(2)));
assert_eq!(expr, Expr::Val(3));
fn eval_nested() {
let expr = Expr::Mul(
Box::new(Expr::Add(Box::new(Expr::Val(1)), Box::new(Expr::Val(2)))),
Box::new(Expr::Val(3)),
);
assert_eq!(expr, Expr::Val(9));
assert_eq!(meta.num_applications, 2);