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use crate::TransformArgs;
use expr::MirRelationExpr;
#[derive(Debug)]
pub struct Negate;
impl crate::Transform for Negate {
fn transform(
&self,
relation: &mut MirRelationExpr,
_: TransformArgs,
) -> Result<(), crate::TransformError> {
relation.try_visit_mut_pre(&mut |e| Ok(self.action(e)))
}
}
impl Negate {
pub fn action(&self, relation: &mut MirRelationExpr) {
if let MirRelationExpr::Negate { input } = relation {
let mut require_negate = true;
while let MirRelationExpr::Negate { input: inner_input } = &mut **input {
**input = inner_input.take_dangerous();
require_negate = !require_negate;
}
if !require_negate {
*relation = input.take_dangerous();
}
}
}
}