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use std::str::FromStr;
use thiserror::Error;
use crate::*;
#[derive(Debug, PartialEq, Clone)]
pub struct MultiPattern<L> {
asts: Vec<(Var, PatternAst<L>)>,
program: machine::Program<L>,
}
impl<L: Language> MultiPattern<L> {
pub fn new(asts: Vec<(Var, PatternAst<L>)>) -> Self {
let program = machine::Program::compile_from_multi_pat(&asts);
Self { asts, program }
}
}
#[derive(Debug, Error)]
pub enum MultiPatternParseError<E> {
#[error(transparent)]
PatternParseError(E),
#[error("Bad clause in the multipattern: {0}")]
PatternAssignmentError(String),
#[error(transparent)]
VariableError(<Var as FromStr>::Err),
}
impl<L: Language + FromOp> FromStr for MultiPattern<L> {
type Err = MultiPatternParseError<<PatternAst<L> as FromStr>::Err>;
fn from_str(s: &str) -> Result<Self, Self::Err> {
use MultiPatternParseError::*;
let mut asts = vec![];
for split in s.trim().split(',') {
let split = split.trim();
if split.is_empty() {
continue;
}
let mut parts = split.split('=');
let vs: &str = parts
.next()
.ok_or_else(|| PatternAssignmentError(split.into()))?;
let v: Var = vs.trim().parse().map_err(VariableError)?;
let ps = parts
.map(|p| p.trim().parse())
.collect::<Result<Vec<PatternAst<L>>, _>>()
.map_err(PatternParseError)?;
if ps.is_empty() {
return Err(PatternAssignmentError(split.into()));
}
asts.extend(ps.into_iter().map(|p| (v, p)))
}
Ok(MultiPattern::new(asts))
}
}
impl<L: Language, A: Analysis<L>> Searcher<L, A> for MultiPattern<L> {
fn search_eclass_with_limit(
&self,
egraph: &EGraph<L, A>,
eclass: Id,
limit: usize,
) -> Option<SearchMatches<L>> {
let substs = self.program.run_with_limit(egraph, eclass, limit);
if substs.is_empty() {
None
} else {
Some(SearchMatches {
eclass,
substs,
ast: None,
})
}
}
fn vars(&self) -> Vec<Var> {
let mut vars = vec![];
for (v, pat) in &self.asts {
vars.push(*v);
for n in pat.as_ref() {
if let ENodeOrVar::Var(v) = n {
vars.push(*v)
}
}
}
vars.sort();
vars.dedup();
vars
}
}
impl<L: Language, A: Analysis<L>> Applier<L, A> for MultiPattern<L> {
fn apply_one(
&self,
_egraph: &mut EGraph<L, A>,
_eclass: Id,
_subst: &Subst,
_searcher_ast: Option<&PatternAst<L>>,
_rule_name: Symbol,
) -> Vec<Id> {
panic!("Multipatterns do not support apply_one")
}
fn apply_matches(
&self,
egraph: &mut EGraph<L, A>,
matches: &[SearchMatches<L>],
_rule_name: Symbol,
) -> Vec<Id> {
let mut added = vec![];
for mat in matches {
for subst in &mat.substs {
let mut subst = subst.clone();
let mut id_buf = vec![];
for (i, (v, p)) in self.asts.iter().enumerate() {
id_buf.resize(p.as_ref().len(), 0.into());
let id1 = crate::pattern::apply_pat(&mut id_buf, p.as_ref(), egraph, &subst);
if let Some(id2) = subst.insert(*v, id1) {
egraph.union(id1, id2);
}
if i == 0 {
added.push(id1)
}
}
}
}
added
}
fn vars(&self) -> Vec<Var> {
let mut bound_vars = HashSet::default();
let mut vars = vec![];
for (bv, pat) in &self.asts {
for n in pat.as_ref() {
if let ENodeOrVar::Var(v) = n {
if !bound_vars.contains(v) {
vars.push(*v)
}
}
}
bound_vars.insert(bv);
}
vars.sort();
vars.dedup();
vars
}
}
#[cfg(test)]
mod tests {
use crate::{SymbolLang as S, *};
type EGraph = crate::EGraph<S, ()>;
impl EGraph {
fn add_string(&mut self, s: &str) -> Id {
self.add_expr(&s.parse().unwrap())
}
}
#[test]
#[should_panic = "unbound var ?z"]
fn bad_unbound_var() {
let _: Rewrite<S, ()> = multi_rewrite!("foo"; "?x = (foo ?y)" => "?x = ?z");
}
#[test]
fn ok_unbound_var() {
let _: Rewrite<S, ()> = multi_rewrite!("foo"; "?x = (foo ?y)" => "?z = (baz ?y), ?x = ?z");
}
#[test]
fn multi_patterns() {
crate::init_logger();
let mut egraph = EGraph::default();
let _ = egraph.add_expr(&"(f a a)".parse().unwrap());
let ab = egraph.add_expr(&"(f a b)".parse().unwrap());
let ac = egraph.add_expr(&"(f a c)".parse().unwrap());
egraph.union(ab, ac);
egraph.rebuild();
let n_matches = |multipattern: &str| -> usize {
let mp: MultiPattern<S> = multipattern.parse().unwrap();
mp.n_matches(&egraph)
};
assert_eq!(n_matches("?x = (f a a), ?y = (f ?c b)"), 1);
assert_eq!(n_matches("?x = (f a a), ?y = (f a b)"), 1);
assert_eq!(n_matches("?x = (f a a), ?y = (f a a)"), 1);
assert_eq!(n_matches("?x = (f ?a ?b), ?y = (f ?c ?d)"), 9);
assert_eq!(n_matches("?x = (f ?a a), ?y = (f ?a b)"), 1);
assert_eq!(n_matches("?x = (f a a), ?x = (f a c)"), 0);
assert_eq!(n_matches("?x = (f a b), ?x = (f a c)"), 1);
}
#[test]
fn unbound_rhs() {
let mut egraph = EGraph::default();
let _x = egraph.add_expr(&"(x)".parse().unwrap());
let rules = vec![
multi_rewrite!("rule1"; "?x = (x)" => "?y = (y), ?y = (z)"),
multi_rewrite!("rule2"; "?x = (x), ?y = (y), ?z = (z)" => "?y = (y), ?y = (z)"),
];
let mut runner = Runner::default().with_egraph(egraph).run(&rules);
let y = runner.egraph.add_expr(&"(y)".parse().unwrap());
let z = runner.egraph.add_expr(&"(z)".parse().unwrap());
assert_eq!(runner.egraph.find(y), runner.egraph.find(z));
}
#[test]
fn ctx_transfer() {
let mut egraph = EGraph::default();
egraph.add_string("(lte ctx1 ctx2)");
egraph.add_string("(lte ctx2 ctx2)");
egraph.add_string("(lte ctx1 ctx1)");
let x2 = egraph.add_string("(tag x ctx2)");
let y2 = egraph.add_string("(tag y ctx2)");
let z2 = egraph.add_string("(tag z ctx2)");
let x1 = egraph.add_string("(tag x ctx1)");
let y1 = egraph.add_string("(tag y ctx1)");
let z1 = egraph.add_string("(tag z ctx2)");
egraph.union(x1, y1);
egraph.union(y2, z2);
let rules = vec![multi_rewrite!("context-transfer";
"?x = (tag ?a ?ctx1) = (tag ?b ?ctx1),
?t = (lte ?ctx1 ?ctx2),
?a1 = (tag ?a ?ctx2),
?b1 = (tag ?b ?ctx2)"
=>
"?a1 = ?b1")];
let runner = Runner::default().with_egraph(egraph).run(&rules);
assert_eq!(runner.egraph.find(x1), runner.egraph.find(y1));
assert_eq!(runner.egraph.find(y2), runner.egraph.find(z2));
assert_eq!(runner.egraph.find(x2), runner.egraph.find(y2));
assert_eq!(runner.egraph.find(x2), runner.egraph.find(z2));
assert_ne!(runner.egraph.find(y1), runner.egraph.find(z1));
assert_ne!(runner.egraph.find(x1), runner.egraph.find(z1));
}
}