Implemented the program

app/Main.hs

@@ -2,5 +2,50 @@ module Main (main) where
 
 import Lib
 
+import qualified Data.Set as Set
+import qualified Data.Map as Map
+import Data.Either (rights, lefts)
+import Data.List (intercalate)
+
+parseInputLine :: Int -> String -> Either ParseError Expression
+parseInputLine n s = parseFullString ("stdin:" ++ show n) s
+
+title :: [String] -> String
+title ns = " " ++ intercalate " | " ns
+
+header :: [Int] -> String
+header ws = intercalate "|" . map (flip replicate '-' . (+2) ) $ ws
+
+row :: [Int] -> [Bool] -> String
+row ws rs = intercalate "|" $ (zipWith row' ws rs)
+    where
+        row' :: Int -> Bool -> String
+        row' w b = replicate (left+1) ' ' ++ (if b then "1" else "0") ++ replicate (right+1) ' '
+            where
+                left  = (w-1) `div` 2
+                right = (w-1) - left
+
 main :: IO ()
-main = someFunc
+main = do
+    equation_strings <- fmap lines getContents
+    let equation_expressions = zipWith parseInputLine [0..] equation_strings
+
+-- TODO: Show proper error messages
+    _ <- mapM putStrLn . map show . lefts $ equation_expressions
+
+    let variable_names     = Set.toAscList . Set.unions . map collectVariableNames . rights $ equation_expressions
+    let value_combinations = mapM (const [True, False]) [1..length variable_names]
+    let value_maps         = map Map.fromList $ zipWith (zipWith (,)) (cycle [variable_names]) value_combinations
+
+    let expression_strings = variable_names ++ equation_strings
+    let column_widths      = map length expression_strings
+
+    putStrLn . title  $ expression_strings
+    putStrLn . header $ column_widths
+
+    let expressions        = rights $ map (parseFullString "<internal>") variable_names ++ equation_expressions
+
+    let results = map (\m -> map (evaluate m) expressions) value_maps
+
+    mapM_ putStrLn . map (row column_widths) $ results
+

package.yaml

@@ -21,6 +21,8 @@ description:         Please see the README on GitHub at <https://github.com/gith
 
 dependencies:
 - base >= 4.7 && < 5
+- parsec
+- containers
 
 ghc-options:
 - -Wall

src/Lib.hs

@@ -1,6 +1,79 @@
 module Lib
-    ( someFunc
+    ( parseFullString, evaluate, collectVariableNames, Expression, ParseError
     ) where
 
-someFunc :: IO ()
+import Text.Parsec
-someFunc = putStrLn "someFunc"
+import Text.Parsec.Expr
+import Text.Parsec.Token
+import Text.Parsec.Language
+
+import Data.Set (Set)
+import qualified Data.Set as Set
+
+import Data.Map (Map)
+import qualified Data.Map as Map
+
+import Data.Functor.Identity
+
+data Expression = Constant Bool | Binary BinaryOperator Expression Expression | Unary UnaryOperator Expression | Variable String
+    deriving Show
+data BinaryOperator = LogicalAnd | LogicalOr
+    deriving Show
+data UnaryOperator  = LogicalNot
+    deriving Show
+
+def :: GenLanguageDef String u Identity
+def = emptyDef{ commentStart = ""
+              , commentEnd = ""
+              , identStart = letter <|> char '_'
+              , identLetter = alphaNum <|> char '_'
+              , opStart = oneOf "&|~"
+              , opLetter = oneOf "&|~"
+              , reservedOpNames = ["&", "|", "~"]
+              , reservedNames = ["true", "false"]
+              }
+
+TokenParser{ parens = m_parens
+           , identifier = m_identifier
+           , reservedOp = m_reservedOp
+           , reserved   = m_reserved
+           , whiteSpace = m_whiteSpace } = makeTokenParser def
+
+exprparser :: ParsecT String () Identity Expression
+exprparser = buildExpressionParser table term <?> "expression"
+
+table :: [[Operator String u Identity Expression]]
+table = [
+            [
+                Prefix (m_reservedOp "~" >> return (Unary LogicalNot))
+            ],
+            [
+                Infix (m_reservedOp "&" >> return (Binary LogicalAnd)) AssocLeft
+            ],
+            [
+                Infix (m_reservedOp "|" >> return (Binary LogicalOr)) AssocLeft
+            ]
+        ]
+
+term :: ParsecT String () Data.Functor.Identity.Identity Expression
+term = m_parens exprparser
+    <|> fmap Variable (m_identifier)
+    <|> (m_reserved "true"  >> return (Constant True))
+    <|> (m_reserved "false" >> return (Constant False))
+    <?> "logical expression"
+
+parseFullString :: SourceName -> String -> Either ParseError Expression
+parseFullString = parse (m_whiteSpace *> exprparser <* eof)
+
+collectVariableNames :: Expression -> Set String
+collectVariableNames (Constant _)          = Set.empty
+collectVariableNames (Binary _ left right) = Set.union (collectVariableNames left) (collectVariableNames right)
+collectVariableNames (Unary _ right)       = collectVariableNames right
+collectVariableNames (Variable name)       = Set.singleton name
+
+evaluate :: Map String Bool -> Expression -> Bool
+evaluate _  (Constant b)              = b
+evaluate vs (Unary    LogicalNot e)   = not (evaluate vs e)
+evaluate vs (Binary   LogicalAnd l r) = evaluate vs l && evaluate vs r
+evaluate vs (Binary   LogicalOr  l r) = evaluate vs l || evaluate vs r
+evaluate vs (Variable name)           = maybe False id (Map.lookup name vs)

stack.yaml.lock

@@ -0,0 +1,13 @@
+# This file was autogenerated by Stack.
+# You should not edit this file by hand.
+# For more information, please see the documentation at:
+#   https://docs.haskellstack.org/en/stable/lock_files
+
+packages: []
+snapshots:
+- completed:
+    sha256: edbd50d7e7c85c13ad5f5835ae2db92fab1e9cf05ecf85340e2622ec0a303df1
+    size: 720020
+    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/22/34.yaml
+  original:
+    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/22/34.yaml

wwffwfwf.cabal

@@ -6,6 +6,7 @@ cabal-version: 2.2
 
 name:           wwffwfwf
 version:        0.1.0.0
+synopsis:       it's true because it works
 description:    Please see the README on GitHub at <https://github.com/githubuser/wwffwfwf#readme>
 homepage:       https://github.com/githubuser/wwffwfwf#readme
 bug-reports:    https://github.com/githubuser/wwffwfwf/issues
@@ -35,6 +36,8 @@ library
   ghc-options: -Wall -Wcompat -Widentities -Wincomplete-record-updates -Wincomplete-uni-patterns -Wmissing-export-lists -Wmissing-home-modules -Wpartial-fields -Wredundant-constraints
   build-depends:
       base >=4.7 && <5
+    , containers
+    , parsec
   default-language: Haskell2010
 
 executable wwffwfwf-exe
@@ -48,6 +51,8 @@ executable wwffwfwf-exe
   ghc-options: -Wall -Wcompat -Widentities -Wincomplete-record-updates -Wincomplete-uni-patterns -Wmissing-export-lists -Wmissing-home-modules -Wpartial-fields -Wredundant-constraints -threaded -rtsopts -with-rtsopts=-N
   build-depends:
       base >=4.7 && <5
+    , containers
+    , parsec
     , wwffwfwf
   default-language: Haskell2010
 
@@ -63,5 +68,7 @@ test-suite wwffwfwf-test
   ghc-options: -Wall -Wcompat -Widentities -Wincomplete-record-updates -Wincomplete-uni-patterns -Wmissing-export-lists -Wmissing-home-modules -Wpartial-fields -Wredundant-constraints -threaded -rtsopts -with-rtsopts=-N
   build-depends:
       base >=4.7 && <5
+    , containers
+    , parsec
     , wwffwfwf
   default-language: Haskell2010