From: Luke Lau <luke_lau@icloud.com>
Date: Sat, 18 May 2019 19:32:54 +0000 (+0100)
Subject: Parse parentheses
X-Git-Url: https://git.lukelau.me/?p=kaleidoscope-hs.git;a=commitdiff_plain;h=2f3c8f5cb6c8b9e6f5be02b20910f8105a9011a6;hp=8a66ac4f81c3d1eab3b13a9e58cee0098573eff1

Parse parentheses

Yes, it's that easy. Try out the difference between
1 * 2 + 3
and
1 * (2 + 3)
---

diff --git a/AST.hs b/AST.hs
index 7dad3a1..e491b64 100644
--- a/AST.hs
+++ b/AST.hs
@@ -13,7 +13,7 @@ data BinOp = Add | Sub | Mul | Cmp Ordering
   deriving Show
 
 instance Read Expr where
-  readPrec = choice [ parseNum
+  readPrec = parens $ choice [ parseNum
                              , parseVar
                              , parseBinOp "<" 10 (Cmp LT)
                              , parseBinOp "+" 20 Add