From a4029222fd6aa7374b394a40dd32bd418ee3ca00 Mon Sep 17 00:00:00 2001
From: Jack Grigg <jack@electriccoin.co>
Date: Wed, 23 Dec 2020 16:13:44 +0000
Subject: [PATCH] book: Fix book tests by adding missing definitions to SHA-256
 page

---
 book/src/design/gadgets/sha256.md | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/book/src/design/gadgets/sha256.md b/book/src/design/gadgets/sha256.md
index daff12f7..226fae6c 100644
--- a/book/src/design/gadgets/sha256.md
+++ b/book/src/design/gadgets/sha256.md
@@ -18,6 +18,15 @@ gadget to consume input in 32-bit chunks.
 The SHA-256 gadget requires a chip with the following instructions:
 
 ```rust
+# extern crate halo2;
+# use halo2::plonk::Error;
+# use std::fmt;
+#
+# trait Chip: Sized {}
+# trait Layouter<C: Chip> {}
+const BLOCK_SIZE: usize = 16;
+const DIGEST_SIZE: usize = 8;
+
 pub trait Sha256Instructions: Chip {
     /// Variable representing the SHA-256 internal state.
     type State: Clone + fmt::Debug;