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|
use super::super::{
ast::{Alt, Call, Cat, Epsilon, Fix, Literal, Parameter, Variable},
visit::{Visitable, Visitor},
};
/// Test if term is closed for a context with `depth` variables.
#[derive(Copy, Clone, Debug, Default)]
pub struct Closed {
depth: usize,
params: usize,
}
impl Visitor for Closed {
type Out = bool;
fn visit_epsilon(&mut self, _eps: &Epsilon) -> Self::Out {
true
}
fn visit_literal(&mut self, _lit: &Literal) -> Self::Out {
true
}
fn visit_cat(&mut self, cat: &Cat) -> Self::Out {
cat.first().visit(self) && cat.second().visit(self)
}
fn visit_alt(&mut self, alt: &Alt) -> Self::Out {
alt.left().visit(self) && alt.right().visit(self)
}
fn visit_fix(&mut self, fix: &Fix) -> Self::Out {
self.depth += 1;
let res = fix.inner().visit(self);
self.depth -= 1;
res
}
fn visit_variable(&mut self, var: &Variable) -> Self::Out {
var.index() < self.depth
}
fn visit_parameter(&mut self, param: &Parameter) -> Self::Out {
param.index() < self.params
}
fn visit_call(&mut self, call: &Call) -> Self::Out {
call.args().iter().all(|arg| arg.visit(self))
}
}
|
