From ddfff57b91a701e2f1d99f0bf2d80d2441b360b8 Mon Sep 17 00:00:00 2001
From: Nicolas Abril <nicolas.abril@protonmail.ch>
Date: Tue, 6 Aug 2024 14:00:09 +0200
Subject: [PATCH] Fix readback when hvm net has `a{n}` or `x{n}` vars

---
 CHANGELOG.md          | 2 ++
 src/net/hvm_to_net.rs | 7 ++++---
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index b8a582ff6..7d57b3307 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,7 @@ and this project does not currently adhere to a particular versioning scheme.
 - Fix local definitions not being desugared properly. ([#623][gh-623])
 - Expand references to functions generated by the `float_combinators` pass inside the main function. ([#642][gh-642])
 - Expand references inside constructors in the main function. ([#643][gh-643])
+- Fix readback when hvm net has `a{n}` or `x{n}` vars. ([#659][gh-659])
 
 ### Added
 
@@ -416,4 +417,5 @@ and this project does not currently adhere to a particular versioning scheme.
 [gh-642]: https://github.com/HigherOrderCO/Bend/issues/642
 [gh-643]: https://github.com/HigherOrderCO/Bend/issues/643
 [gh-648]: https://github.com/HigherOrderCO/Bend/issues/648
+[gh-659]: https://github.com/HigherOrderCO/Bend/pull/659
 [Unreleased]: https://github.com/HigherOrderCO/Bend/compare/0.2.36...HEAD
diff --git a/src/net/hvm_to_net.rs b/src/net/hvm_to_net.rs
index 18f7c189a..047ba2dd7 100644
--- a/src/net/hvm_to_net.rs
+++ b/src/net/hvm_to_net.rs
@@ -23,7 +23,8 @@ fn hvm_to_inodes(net: &Net) -> INodes {
 
   // Convert all the trees forming active pairs.
   for (i, (_, tree1, tree2)) in net.rbag.iter().enumerate() {
-    let tree_root = format!("a{i}");
+    // This name cannot appear anywhere in the original net
+    let tree_root = format!("%a{i}");
     let mut tree1 = tree_to_inodes(tree1, tree_root.clone(), net_root, &mut n_vars);
     inodes.append(&mut tree1);
     let mut tree2 = tree_to_inodes(tree2, tree_root, net_root, &mut n_vars);
@@ -33,7 +34,8 @@ fn hvm_to_inodes(net: &Net) -> INodes {
 }
 
 fn new_var(n_vars: &mut NodeId) -> String {
-  let new_var = format!("x{n_vars}");
+  // This name cannot appear anywhere in the original net
+  let new_var = format!("%x{n_vars}");
   *n_vars += 1;
   new_var
 }
@@ -46,7 +48,6 @@ fn tree_to_inodes(tree: &Tree, tree_root: String, net_root: &str, n_vars: &mut N
     n_vars: &mut NodeId,
   ) -> String {
     if let Tree::Var { nam } = subtree {
-      //
       if nam == net_root {
         "_".to_string()
       } else {