From b8bd18e7420d0b7b44f0b473c76d4e078c2057b6 Mon Sep 17 00:00:00 2001
From: Rob Rix <rob.rix@me.com>
Date: Wed, 3 May 2017 11:26:53 -0400
Subject: [PATCH] Define binary subtraction syntax.

---
 src/Data/Syntax/Expression.hs | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/Data/Syntax/Expression.hs b/src/Data/Syntax/Expression.hs
index e10a8e82f..f44aa8e6b 100644
--- a/src/Data/Syntax/Expression.hs
+++ b/src/Data/Syntax/Expression.hs
@@ -27,3 +27,10 @@ data Plus a = Plus a a
 
 instance Eq1 Plus where liftEq = genericLiftEq
 instance Show1 Plus where liftShowsPrec = genericLiftShowsPrec
+
+-- | Binary subtraction.
+data Minus a = Minus a a
+  deriving (Eq, Foldable, Functor, Generic1, Show, Traversable)
+
+instance Eq1 Minus where liftEq = genericLiftEq
+instance Show1 Minus where liftShowsPrec = genericLiftShowsPrec