basic arithmetic DSL

haskell-experiments/.idea/material_theme_project_new.xml

@@ -3,7 +3,9 @@
   <component name="MaterialThemeProjectNewConfig">
     <option name="metadata">
       <MTProjectMetadataState>
-        <option name="userId" value="-70c0f615:19bbbe81457:-7f6e" />
+        <option name="migrated" value="true" />
+        <option name="pristineConfig" value="false" />
+        <option name="userId" value="-4395108f:199cee938a2:-7ff9" />
       </MTProjectMetadataState>
     </option>
   </component>

haskell-experiments/haskell-experiments.cabal

@@ -78,13 +78,13 @@ test-suite haskell-exps-test
 
     -- Test dependencies.
     build-depends:    base, hspec, langfeatures
-    other-modules:    Test.OlogsSpec
+    other-modules:    Test.OlogsSpec,
-
+        Test.SimpleParserSpec
 
 library langfeatures
-  build-depends:   base, containers
+  build-depends:   base, containers, megaparsec
   hs-source-dirs:  src
-  exposed-modules: Ologs
+  exposed-modules: Ologs, SimpleParser
   ghc-options:     -Wall
 
 executable haskell-experiments

haskell-experiments/src/SimpleParser.hs

@@ -0,0 +1,41 @@
+{-# LANGUAGE BlockArguments #-}
+{-# LANGUAGE DuplicateRecordFields #-}
+{-# LANGUAGE NamedFieldPuns #-}
+{-# LANGUAGE OverloadedRecordDot #-}
+{-# HLINT ignore "Unused LANGUAGE pragma" #-}
+{-# HLINT ignore "Use concatMap" #-}
+{-# LANGUAGE RecordWildCards #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TypeApplications #-}
+{-# HLINT ignore "Move catMaybes" #-}
+{-# HLINT ignore "Use mapMaybe" #-}
+{-# HLINT ignore "Use list comprehension" #-}
+{-# LANGUAGE TypeOperators #-}
+{-# LANGUAGE NoFieldSelectors #-}
+{-# LANGUAGE NoMonomorphismRestriction #-}
+{-# OPTIONS_GHC -Wno-unrecognised-pragmas #-}
+
+module SimpleParser
+  ( eval, Expr (..) )
+where
+import Text.Megaparsec
+import Data.Void (Void)
+
+type Parser = Parsec Void String
+
+data Expr =
+  Add Expr Expr |
+  Subtract Expr Expr |
+  Multiply Expr Expr |
+  Divide Expr Expr |
+  Negate Expr |
+  Literal Int 
+
+eval :: Expr -> Int
+eval (Literal n) = n
+eval (Add a b) = (eval a) + (eval b)
+eval (Subtract a b) = (eval a) - (eval b)
+eval (Multiply a b) = (eval a) * (eval b)
+eval (Divide a b) = (eval a) `div` (eval b)
+eval (Negate a) =  -(eval a)
+

haskell-experiments/test/Main.hs

@@ -2,10 +2,12 @@ module Main (main) where
 import Test.Hspec
 
 import qualified Test.OlogsSpec as Ologs
+import qualified Test.SimpleParserSpec as SimpleParserSpec
 --import Test.FooSpec
 
 main :: IO ()
 main = hspec $ do
     describe "Ologs" Ologs.spec
+    describe "SimpleParser" SimpleParserSpec.spec
 --    describe "My amazing tests" [ FastLaneSpec FooSpec ]
 

haskell-experiments/test/Test/SimpleParserSpec.hs

@@ -0,0 +1,26 @@
+{-# LANGUAGE DuplicateRecordFields #-}
+{-# LANGUAGE OverloadedRecordDot #-}
+{-# HLINT ignore "Use const" #-}
+{-# HLINT ignore "Unused LANGUAGE pragma" #-}
+{-# HLINT ignore "Avoid lambda" #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE NoFieldSelectors #-}
+{-# OPTIONS_GHC -Wno-unrecognised-pragmas #-}
+{-# LANGUAGE TypeApplications #-}
+
+module Test.SimpleParserSpec where
+
+import Test.Hspec
+
+import SimpleParser
+
+spec :: Spec
+spec = do
+  describe "evaluate expressions" $ do
+    it "arithmetic on literals" $ do
+      eval (Add (Literal 2) (Literal 3) ) `shouldBe` 5
+      eval (Subtract (Literal 2) (Literal 3) ) `shouldBe` -1
+      eval (Multiply (Literal 2) (Literal 3) ) `shouldBe` 6
+      eval (Divide (Literal 7) (Literal 3) ) `shouldBe` 2
+
+