From a0b31174f4b7f6ac037dc4002c38cd61b09dabaa Mon Sep 17 00:00:00 2001
From: Luke Lau <luke_lau@icloud.com>
Date: Sun, 10 Mar 2019 01:18:24 +0000
Subject: [PATCH] Begin parsing addition

---
 AST.hs | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)
 create mode 100644 AST.hs

diff --git a/AST.hs b/AST.hs
new file mode 100644
index 0000000..6528215
--- /dev/null
+++ b/AST.hs
@@ -0,0 +1,20 @@
+module AST where
+
+import Text.Read
+import Text.ParserCombinators.ReadP hiding ((+++))
+
+data Expr = Num Float
+          | Add Expr Expr
+  deriving Show
+
+instance Read Expr where
+  readPrec = parseNum +++ parseAdd
+    where parseNum = Num <$> readPrec
+          parseAdd = step $ do
+            a <- prec 11 readPrec
+            lift $ do
+              skipSpaces
+              char '+'
+              skipSpaces
+            b <- readPrec
+            return (Add a b)
-- 
2.30.2