From dc10a278cca74d737e4af0fe034a1caa8abb291d Mon Sep 17 00:00:00 2001
From: Greg Brown <gmb60@cam.ac.uk>
Date: Wed, 6 Jan 2021 14:56:11 +0000
Subject: Restructure code base to separate compilation phases.

---
 src/lower/mod.rs | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)
 create mode 100644 src/lower/mod.rs

(limited to 'src/lower/mod.rs')

diff --git a/src/lower/mod.rs b/src/lower/mod.rs
new file mode 100644
index 0000000..242fa47
--- /dev/null
+++ b/src/lower/mod.rs
@@ -0,0 +1,58 @@
+use crate::chomp::typed::{
+    Alt, Cat, Epsilon, Fix, Literal, RawTypedExpression, TypedExpression, Variable,
+};
+
+pub mod rust;
+
+pub trait Backend: Default {
+    type Id;
+    type Code;
+
+    fn gen_epsilon(&mut self, eps: Epsilon) -> Self::Id;
+
+    fn gen_literal(&mut self, lit: Literal) -> Self::Id;
+
+    fn gen_cat(&mut self, cat: Cat) -> Self::Id;
+
+    fn gen_alt(&mut self, alt: Alt) -> Self::Id;
+
+    fn gen_fix(&mut self, fix: Fix) -> Self::Id;
+
+    fn gen_variable(&mut self, var: Variable) -> Self::Id;
+
+    fn emit_code(self, id: Self::Id) -> Self::Code;
+}
+
+pub trait GenerateCode {
+    fn gen<B: Backend>(self, backend: &mut B) -> B::Id;
+}
+
+macro_rules! generate_leaf {
+    ($ty:ty, $gen:ident) => {
+        impl GenerateCode for $ty {
+            fn gen<B: Backend>(self, backend: &mut B) -> B::Id {
+                backend.$gen(self)
+            }
+        }
+    };
+}
+
+generate_leaf!(Epsilon, gen_epsilon);
+generate_leaf!(Literal, gen_literal);
+generate_leaf!(Cat, gen_cat);
+generate_leaf!(Alt, gen_alt);
+generate_leaf!(Fix, gen_fix);
+generate_leaf!(Variable, gen_variable);
+
+impl GenerateCode for TypedExpression {
+    fn gen<B: Backend>(self, backend: &mut B) -> B::Id {
+        match self.inner {
+            RawTypedExpression::Epsilon(e) => e.gen(backend),
+            RawTypedExpression::Literal(l) => l.gen(backend),
+            RawTypedExpression::Cat(c) => c.gen(backend),
+            RawTypedExpression::Alt(a) => a.gen(backend),
+            RawTypedExpression::Fix(f) => f.gen(backend),
+            RawTypedExpression::Variable(v) => v.gen(backend),
+        }
+    }
+}
-- 
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