From 51aeade75d5289fff417414b04bae5be0862fd8f Mon Sep 17 00:00:00 2001
From: Luke Lau <luke_lau@icloud.com>
Date: Sun, 10 Mar 2019 12:37:36 +0000
Subject: [PATCH] Add support for more binary ops

---
 AST.hs  | 18 ++++++++++++------
 Main.hs |  8 ++++++--
 2 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/AST.hs b/AST.hs
index 6528215..424cfbe 100644
--- a/AST.hs
+++ b/AST.hs
@@ -1,20 +1,26 @@
 module AST where
 
 import Text.Read
-import Text.ParserCombinators.ReadP hiding ((+++))
+import Text.ParserCombinators.ReadP hiding ((+++), choice)
 
+data BinOpType = Add | Sub | Mul
+  deriving Show
 data Expr = Num Float
-          | Add Expr Expr
+          | BinOp BinOpType Expr Expr
   deriving Show
 
 instance Read Expr where
-  readPrec = parseNum +++ parseAdd
+  readPrec = choice [ parseNum
+                    , parseBinOp '+' Add
+                    , parseBinOp '-' Sub
+                    , parseBinOp '*' Mul
+                    ]
     where parseNum = Num <$> readPrec
-          parseAdd = step $ do
+          parseBinOp c typ = step $ do
             a <- prec 11 readPrec
             lift $ do
               skipSpaces
-              char '+'
+              char c
               skipSpaces
             b <- readPrec
-            return (Add a b)
+            return (BinOp typ a b)
diff --git a/Main.hs b/Main.hs
index 2d838d3..8f4610a 100644
--- a/Main.hs
+++ b/Main.hs
@@ -35,7 +35,11 @@ main = do
 
 build :: AST.Expr -> IRBuilderT ModuleBuilder Operand
 build (AST.Num a) = pure $ ConstantOperand (Float (Single a))
-build (AST.Add a b) = do
+build (AST.BinOp op a b) = do
   va <- build a
   vb <- build b
-  fadd va vb
+  let instr = case op of
+                AST.Add -> fadd
+                AST.Sub -> fsub
+                AST.Mul -> fmul
+  instr va vb
-- 
2.30.2