revamped expressions

haskell-experiments/src/SimpleParser.hs

@@ -16,26 +16,54 @@
 {-# OPTIONS_GHC -Wno-unrecognised-pragmas #-}
 
 module SimpleParser
-  ( eval, Expr (..) )
+  ( eval, Expr (..), BinaryOp (..), UnaryOp (..) ) -- literalParser
 where
 import Text.Megaparsec
 import Data.Void (Void)
+import Text.Megaparsec.Byte.Lexer (decimal)
+import Control.Concurrent (yield)
 
 type Parser = Parsec Void String
 
+data BinaryOp = Add | Subtract | Multiply | Divide
+
+data UnaryOp = Negate
+
 data Expr =
-  Add Expr Expr |
+  BinaryExpr BinaryOp Expr Expr |
-  Subtract Expr Expr |
+  UnaryExpr UnaryOp Expr |
-  Multiply Expr Expr |
-  Divide Expr Expr |
-  Negate Expr |
   Literal Int 
 
+lookUpBinaryOp :: BinaryOp -> Int -> Int -> Int
+lookUpBinaryOp Add = (+)
+lookUpBinaryOp Subtract = (-)
+lookUpBinaryOp Multiply = (*)
+lookUpBinaryOp Divide = div
+
+lookUpUnaryOp :: UnaryOp -> Int -> Int
+lookUpUnaryOp Negate x = -x
+
 eval :: Expr -> Int
 eval (Literal n) = n
-eval (Add a b) = (eval a) + (eval b)
+eval (BinaryExpr binOp a b) = lookUpBinaryOp binOp (eval a) (eval b)
-eval (Subtract a b) = (eval a) - (eval b)
+eval (UnaryExpr unaryOp a) =  lookUpUnaryOp unaryOp (eval a)
-eval (Multiply a b) = (eval a) * (eval b)
-eval (Divide a b) = (eval a) `div` (eval b)
-eval (Negate a) =  -(eval a)
 
+
+-- parseExpr :: Parser Expr
+-- parseExpr = choice [
+--     literalParser,
+--     expressionParser
+--     -- bracketedExpParser,
+--     -- negatedExp
+--   ]
+  
+-- literalParser :: Parser Expr
+-- literalParser = Literal <$> decimal
+
+-- expressionParser :: Parser Expr
+-- expressionParser = do
+--   parseExpr
+--   parseOp
+--   parseExpr
+
+-- parseOp :: Parser Expr

haskell-experiments/test/Test/SimpleParserSpec.hs

@@ -18,13 +18,16 @@ spec :: Spec
 spec = do
   describe "evaluate expressions" $ do
     it "arithmetic on literals" $ do
-      eval (Add (Literal 2) (Literal 3) ) `shouldBe` 5
+      eval (BinaryExpr Add (Literal 2) (Literal 3) ) `shouldBe` 5
-      eval (Subtract (Literal 2) (Literal 3) ) `shouldBe` -1
+      eval (BinaryExpr Subtract (Literal 2) (Literal 3) ) `shouldBe` -1
-      eval (Multiply (Literal 2) (Literal 3) ) `shouldBe` 6
+      eval (BinaryExpr Multiply (Literal 2) (Literal 3) ) `shouldBe` 6
-      eval (Divide (Literal 7) (Literal 3) ) `shouldBe` 2
+      eval (BinaryExpr Divide (Literal 7) (Literal 3) ) `shouldBe` 2
-      eval (Negate (Literal 7) ) `shouldBe` -7
+      eval (UnaryExpr Negate (Literal 7) ) `shouldBe` -7
     it "more complex arithmetic on literals" $ do
-      eval (Add (Negate (Literal 1)) (Divide (Literal 7) (Literal 3))) `shouldBe` 1
+      eval (BinaryExpr Add 
+        (UnaryExpr Negate (Literal 1)) 
+        (BinaryExpr Divide (Literal 7) (Literal 3))
+        ) `shouldBe` 1
 
 
 

untitled/.gitignore

@@ -0,0 +1,29 @@
+### IntelliJ IDEA ###
+out/
+!**/src/main/**/out/
+!**/src/test/**/out/
+
+### Eclipse ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+bin/
+!**/src/main/**/bin/
+!**/src/test/**/bin/
+
+### NetBeans ###
+/nbproject/private/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/
+
+### VS Code ###
+.vscode/
+
+### Mac OS ###
+.DS_Store