From: Luke Lau <luke_lau@icloud.com>
Date: Wed, 5 Jun 2019 21:12:52 +0000 (+0100)
Subject: Tidy up the parsing a bit
X-Git-Url: http://git.lukelau.me/?p=kaleidoscope-hs.git;a=commitdiff_plain;h=0d4ed473c520786af90ab70dac51451ea2b8b941

Tidy up the parsing a bit

The Text.ParserCombinators.ReadPrec/Text.ParserCominators.ReadP split
adds a bit of lifting cruft, so lets try to sweep that away.
---

diff --git a/AST.hs b/AST.hs
index 1e505af..ae18a52 100644
--- a/AST.hs
+++ b/AST.hs
@@ -30,10 +30,7 @@ instance Read Expr where
           parseVar = Var <$> lift (munch1 isAlpha)
           parseBinOp s prc op = prec prc $ do
             a <- step readPrec
-            lift $ do
-              skipSpaces
-              string s
-              skipSpaces
+            spaced $ string s
             b <- readPrec
             return (BinOp op a b)
           parseCall = do
@@ -43,13 +40,14 @@ instance Read Expr where
                               (skipSpaces >> char ',' >> skipSpaces)
             return (Call func params)
           parseIf = do
-            lift $ skipSpaces >> string "if" >> skipSpaces
+            spaced $ string "if" 
             cond <- readPrec
-            lift $ skipSpaces >> string "then" >> skipSpaces
+            spaced $ string "then"
             thenE <- readPrec
-            lift $ skipSpaces >> string "else" >> skipSpaces
+            spaced $ string "else"
             elseE <- readPrec
             return (If cond thenE elseE)
+          spaced f = lift $ skipSpaces >> f >> skipSpaces
             
 data Prototype = Prototype String [String]
   deriving Show