From e1452227b8bd9ad3805480f8a5a66a75fb8370dd Mon Sep 17 00:00:00 2001
From: Greg Brown <gmb60@cam.ac.uk>
Date: Fri, 8 Jan 2021 18:00:11 +0000
Subject: Do more restructuring.

---
 src/chomp/check/shallow.rs | 47 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)
 create mode 100644 src/chomp/check/shallow.rs

(limited to 'src/chomp/check/shallow.rs')

diff --git a/src/chomp/check/shallow.rs b/src/chomp/check/shallow.rs
new file mode 100644
index 0000000..e5cc1a1
--- /dev/null
+++ b/src/chomp/check/shallow.rs
@@ -0,0 +1,47 @@
+use super::super::{
+    ast::{Alt, Call, Cat, Epsilon, Fix, Literal, Parameter, Variable},
+    visit::{Mapper, Visitable},
+};
+
+#[derive(Clone, Copy, Debug, Default)]
+pub struct ShallowVars {
+    depth: usize,
+}
+
+impl Mapper for ShallowVars {
+    type Out = ();
+
+    fn map_epsilon(&mut self, _: &mut Epsilon) -> Self::Out {}
+
+    fn map_literal(&mut self, _: &mut Literal) -> Self::Out {}
+
+    fn map_cat(&mut self, cat: &mut Cat) -> Self::Out {
+        cat.first_mut().map(self);
+        cat.second_mut().map(self);
+    }
+
+    fn map_alt(&mut self, alt: &mut Alt) -> Self::Out {
+        alt.left_mut().map(self);
+        alt.right_mut().map(self);
+    }
+
+    fn map_fix(&mut self, fix: &mut Fix) -> Self::Out {
+        self.depth += 1;
+        fix.inner_mut().map(self);
+        self.depth -= 1;
+    }
+
+    fn map_variable(&mut self, bind: &mut Variable) -> Self::Out {
+        if bind.index() > self.depth {
+            *bind.index_mut() -= 1;
+        }
+    }
+
+    fn map_parameter(&mut self, _param: &mut Parameter) -> Self::Out {}
+
+    fn map_call(&mut self, call: &mut Call) -> Self::Out {
+        for arg in call.args_mut() {
+            arg.map(self);
+        }
+    }
+}
-- 
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