Add solving expressions

README.md

@@ -27,3 +27,4 @@ Main repo: https://git.sudoer.ch/me/really-bad-compiler-in-haskell
 - IDE: VSCodium
 - Git platform: Forgejo
 - AI: Phind
+- Search: Kagi, Stack Overflow

app/Eval/Expression.hs

@@ -0,0 +1,13 @@
+module Eval.Expression (evalExpr) where
+
+import Objects.Expression
+
+eval :: Expr -> Int
+eval (Lit x) = x
+eval (Add x y) = eval x + eval y
+eval (Sub x y) = eval x - eval y
+eval (Mul x y) = eval x * eval y
+eval (Div x y) = eval x `div` eval y
+
+evalExpr :: Expr -> Int
+evalExpr = eval

app/Main.hs

@@ -1,10 +1,21 @@
 module Main (main) where
 
-import Parser.Equation
+import Data.Either
+import Eval.Expression
+import Objects.Expression
+import Parser.Expression
 import System.Environment
 import Text.Megaparsec
 
--- main :: IO ()
+parseResult :: ParseResult
+parseResult = parseExpr "2+3*4"
+
+getRight :: ParseResult -> Expr
+getRight (Right r) = r
+
+expr = getRight parseResult
+
+result = evalExpr expr
+
 main = do
-  input <- fmap head getArgs
-  parseTest equationParser input
+  print result

app/Objects/Expression.hs

@@ -0,0 +1,19 @@
+module Objects.Expression
+  ( Expr
+      ( Lit,
+        Add,
+        Sub,
+        Mul,
+        Div
+      ),
+      -- solve,
+  )
+where
+
+data Expr
+  = Lit Int
+  | Add Expr Expr
+  | Sub Expr Expr
+  | Mul Expr Expr
+  | Div Expr Expr
+  deriving (Show)

app/Parser/Expression.hs

@@ -1,21 +1,14 @@
-module Parser.Equation (equationParser) where
+module Parser.Expression (parseExpr, ParseResult) where
 
 import Control.Monad.Combinators.Expr
 import Data.Void (Void)
-import Text.Megaparsec
+import Objects.Expression
+import Text.Megaparsec as MP
 import Text.Megaparsec.Char as C
 import Text.Megaparsec.Char.Lexer as L
 
 type Parser = Parsec Void String
 
-data Expr
-  = Int Int
-  | Add Expr Expr
-  | Sub Expr Expr
-  | Mul Expr Expr
-  | Div Expr Expr
-  deriving (Show)
-
 lexemeParser :: Parser a -> Parser a
 lexemeParser = L.lexeme C.space
 
@@ -26,7 +19,7 @@ intParser :: Parser Int
 intParser = lexemeParser L.decimal
 
 term :: Parser Expr
-term = Int <$> intParser
+term = Lit <$> intParser
 
 table :: [[Operator Parser Expr]]
 table =
@@ -43,7 +36,9 @@ binaryOp name f = InfixL (f <$ symbolParser name)
 expr :: Parser Expr
 expr = makeExprParser term table
 
-parseExpr :: String -> Either (ParseErrorBundle String Void) Expr
-parseExpr = parse (C.space *> expr <* eof) ""
+type ParseResult = Either (ParseErrorBundle String Void) Expr
 
-equationParser = expr
+parseExpr :: String -> ParseResult
+parseExpr = MP.parse (C.space *> expr <* eof) ""
+
+-- parseE = parseExpr