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use conjure_core::ast::{Expression as Expr, Factor, Literal as Lit};
use conjure_core::metadata::Metadata;
use conjure_core::rule_engine::{
register_rule, register_rule_set, ApplicationError, ApplicationResult, Reduction,
};
use conjure_core::Model;
use tracing::warn;
register_rule_set!("Constant", 100, ());
#[register_rule(("Constant", 9001))]
fn apply_eval_constant(expr: &Expr, _: &Model) -> ApplicationResult {
if let Expr::FactorE(_, Factor::Literal(_)) = expr {
return Err(ApplicationError::RuleNotApplicable);
}
eval_constant(expr)
.map(|c| Reduction::pure(Expr::FactorE(Metadata::new(), Factor::Literal(c))))
.ok_or(ApplicationError::RuleNotApplicable)
/// Simplify an expression to a constant if possible
/// Returns:
/// `None` if the expression cannot be simplified to a constant (e.g. if it contains a variable)
/// `Some(Const)` if the expression can be simplified to a constant
pub fn eval_constant(expr: &Expr) -> Option<Lit> {
match expr {
Expr::FactorE(_, Factor::Literal(c)) => Some(c.clone()),
Expr::FactorE(_, Factor::Reference(c)) => None,
Expr::Eq(_, a, b) => bin_op::<i32, bool>(|a, b| a == b, a, b)
.or_else(|| bin_op::<bool, bool>(|a, b| a == b, a, b))
.map(Lit::Bool),
Expr::Neq(_, a, b) => bin_op::<i32, bool>(|a, b| a != b, a, b).map(Lit::Bool),
Expr::Lt(_, a, b) => bin_op::<i32, bool>(|a, b| a < b, a, b).map(Lit::Bool),
Expr::Gt(_, a, b) => bin_op::<i32, bool>(|a, b| a > b, a, b).map(Lit::Bool),
Expr::Leq(_, a, b) => bin_op::<i32, bool>(|a, b| a <= b, a, b).map(Lit::Bool),
Expr::Geq(_, a, b) => bin_op::<i32, bool>(|a, b| a >= b, a, b).map(Lit::Bool),
Expr::Not(_, expr) => un_op::<bool, bool>(|e| !e, expr).map(Lit::Bool),
Expr::And(_, exprs) => vec_op::<bool, bool>(|e| e.iter().all(|&e| e), exprs).map(Lit::Bool),
Expr::Or(_, exprs) => vec_op::<bool, bool>(|e| e.iter().any(|&e| e), exprs).map(Lit::Bool),
Expr::Sum(_, exprs) => vec_op::<i32, i32>(|e| e.iter().sum(), exprs).map(Lit::Int),
Expr::Ineq(_, a, b, c) => {
tern_op::<i32, bool>(|a, b, c| a <= (b + c), a, b, c).map(Lit::Bool)
Expr::SumGeq(_, exprs, a) => {
flat_op::<i32, bool>(|e, a| e.iter().sum::<i32>() >= a, exprs, a).map(Lit::Bool)
Expr::SumLeq(_, exprs, a) => {
flat_op::<i32, bool>(|e, a| e.iter().sum::<i32>() <= a, exprs, a).map(Lit::Bool)
// Expr::Div(_, a, b) => bin_op::<i32, i32>(|a, b| a / b, a, b).map(Lit::Int),
// Expr::SafeDiv(_, a, b) => bin_op::<i32, i32>(|a, b| a / b, a, b).map(Lit::Int),
Expr::Min(_, exprs) => {
opt_vec_op::<i32, i32>(|e| e.iter().min().copied(), exprs).map(Lit::Int)
Expr::Max(_, exprs) => {
opt_vec_op::<i32, i32>(|e| e.iter().max().copied(), exprs).map(Lit::Int)
Expr::UnsafeDiv(_, a, b) | Expr::SafeDiv(_, a, b) => {
if unwrap_expr::<i32>(b)? == 0 {
return None;
bin_op::<i32, i32>(|a, b| a / b, a, b).map(Lit::Int)
Expr::DivEq(_, a, b, c) => {
let a = unwrap_factor::<i32>(a)?;
let b = unwrap_factor::<i32>(b)?;
let c = unwrap_factor::<i32>(c)?;
if b == 0 {
Some(Lit::Bool(a / b == c))
Expr::Bubble(_, a, b) => bin_op::<bool, bool>(|a, b| a && b, a, b).map(Lit::Bool),
Expr::Reify(_, a, b) => bin_op::<bool, bool>(|a, b| a == b, a, b).map(Lit::Bool),
_ => {
warn!(%expr,"Unimplemented constant eval");
None
fn un_op<T, A>(f: fn(T) -> A, a: &Expr) -> Option<A>
where
T: TryFrom<Lit>,
{
let a = unwrap_expr::<T>(a)?;
Some(f(a))
fn bin_op<T, A>(f: fn(T, T) -> A, a: &Expr, b: &Expr) -> Option<A>
let b = unwrap_expr::<T>(b)?;
Some(f(a, b))
fn tern_op<T, A>(f: fn(T, T, T) -> A, a: &Expr, b: &Expr, c: &Expr) -> Option<A>
let c = unwrap_expr::<T>(c)?;
Some(f(a, b, c))
fn vec_op<T, A>(f: fn(Vec<T>) -> A, a: &[Expr]) -> Option<A>
let a = a.iter().map(unwrap_expr).collect::<Option<Vec<T>>>()?;
fn opt_vec_op<T, A>(f: fn(Vec<T>) -> Option<A>, a: &[Expr]) -> Option<A>
f(a)
fn flat_op<T, A>(f: fn(Vec<T>, T) -> A, a: &[Expr], b: &Expr) -> Option<A>
fn unwrap_expr<T: TryFrom<Lit>>(expr: &Expr) -> Option<T> {
let c = eval_constant(expr)?;
TryInto::<T>::try_into(c).ok()
fn unwrap_factor<T: TryFrom<Lit>>(factor: &Factor) -> Option<T> {
let Factor::Literal(c) = factor else {
TryInto::<T>::try_into(c.clone()).ok()
#[cfg(test)]
mod tests {
use conjure_core::ast::{Expression, Factor, Literal};
#[test]
fn div_by_zero() {
let expr = Expression::UnsafeDiv(
Default::default(),
Box::new(Expression::FactorE(
Factor::Literal(Literal::Int(1)),
)),
Factor::Literal(Literal::Int(0)),
);
assert_eq!(super::eval_constant(&expr), None);
fn safediv_by_zero() {
let expr = Expression::SafeDiv(