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//! These tests use a simple constant expression tree to demonstrate the use of the `gen_reduce` crate.
use tree_morph::{helpers::select_first, *};
use uniplate::derive::Uniplate;
#[derive(Debug, Clone, PartialEq, Eq, Uniplate)]
#[uniplate()]
enum Expr {
Add(Box<Expr>, Box<Expr>),
Mul(Box<Expr>, Box<Expr>),
Val(i32),
}
struct Meta {
num_applications: u32,
enum ReductionRule {
AddZero,
MulOne,
Eval,
impl Rule<Expr, Meta> for ReductionRule {
fn apply(&self, cmd: &mut Commands<Expr, Meta>, expr: &Expr, _: &Meta) -> Option<Expr> {
use Expr::*;
use ReductionRule::*;
let result = match self {
AddZero => match expr {
Add(a, b) if matches!(a.as_ref(), Val(0)) => Some(*b.clone()),
Add(a, b) if matches!(b.as_ref(), Val(0)) => Some(*a.clone()),
_ => None,
},
MulOne => match expr {
Mul(a, b) if matches!(a.as_ref(), Val(1)) => Some(*b.clone()),
Mul(a, b) if matches!(b.as_ref(), Val(1)) => Some(*a.clone()),
Eval => match expr {
Add(a, b) => match (a.as_ref(), b.as_ref()) {
(Val(x), Val(y)) => Some(Val(x + y)),
Mul(a, b) => match (a.as_ref(), b.as_ref()) {
(Val(x), Val(y)) => Some(Val(x * y)),
};
if result.is_some() {
cmd.mut_meta(|m| m.num_applications += 1);
result
#[test]
fn test_single_var() {
let expr = Expr::Val(42);
let meta = Meta {
num_applications: 0,
let (expr, meta) = reduce_with_rules(&[ReductionRule::Eval], select_first, expr, meta);
assert_eq!(expr, Expr::Val(42));
assert_eq!(meta.num_applications, 0);
fn test_add_zero() {
let expr = Expr::Add(Box::new(Expr::Val(0)), Box::new(Expr::Val(42)));
let (expr, meta) = reduce_with_rules(&[ReductionRule::AddZero], select_first, expr, meta);
assert_eq!(meta.num_applications, 1);
fn test_mul_one() {
let expr = Expr::Mul(Box::new(Expr::Val(1)), Box::new(Expr::Val(42)));
let (expr, meta) = reduce_with_rules(&[ReductionRule::MulOne], select_first, expr, meta);
fn test_eval_add() {
let expr = Expr::Add(Box::new(Expr::Val(1)), Box::new(Expr::Val(2)));
assert_eq!(expr, Expr::Val(3));
fn test_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);