feat: parse λ-expr with multiple bindings

2 files changed, 15 insertions, 8 deletions

diff --git a/lambda-calcul/haskell/src/Minilang/Lambda/Parser.hs b/lambda-calcul/haskell/src/Minilang/Lambda/Parser.hs
index 545536d..8e97d46 100644
--- a/lambda-calcul/haskell/src/Minilang/Lambda/Parser.hs
+++ b/lambda-calcul/haskell/src/Minilang/Lambda/Parser.hs
@@ -13,7 +13,7 @@ type Parser = Parsec Void Text
 data ParseError = ParseError Text
   deriving (Eq, Show)
 
-data AST = Sym Text | Abs Text AST
+data AST = Sym Text | Abs [Text] AST
   deriving (Eq, Show)
 
 parse :: Text -> Either ParseError AST
@@ -28,10 +28,10 @@ lambda =
   between
     lpar
     rpar
-    ( do
-        lexeme "lam"
-        binding <- pack <$> between lpar rpar identifier
-        Abs binding <$> ast
+    ( lexeme "lam"
+        *> ( (Abs . fmap pack <$> between lpar rpar (many identifier))
+               <*> ast
+           )
     )
 
 lpar :: Parser Text
diff --git a/lambda-calcul/haskell/test/Minilang/Lambda/ParserSpec.hs b/lambda-calcul/haskell/test/Minilang/Lambda/ParserSpec.hs
index c1eab27..ea7cd89 100644
--- a/lambda-calcul/haskell/test/Minilang/Lambda/ParserSpec.hs
+++ b/lambda-calcul/haskell/test/Minilang/Lambda/ParserSpec.hs
@@ -1,19 +1,26 @@
 module Minilang.Lambda.ParserSpec where
 
 import Data.Text (Text, pack)
+import qualified Data.Text as Text
 import Minilang.Lambda.Parser (AST (..), initialChars, parse, restChars)
 import Test.Hspec (Spec, parallel, shouldBe)
 import Test.Hspec.QuickCheck (prop)
-import Test.QuickCheck (Arbitrary (..), elements, listOf)
+import Test.QuickCheck (Arbitrary (..), NonEmptyList (..), elements, listOf)
 
 spec :: Spec
 spec = parallel $ do
   prop "parses an identifier as a variable" $ \(Identifier ident) ->
     parse ident `shouldBe` Right (Sym ident)
+
   prop "parses a lambda-expression as an abstraction" $ \(Identifier ident) (Identifier body) ->
-    parse ("(lam (" <> ident <> ") " <> body <> ")") `shouldBe` Right (Abs ident (Sym body))
+    parse ("(lam (" <> ident <> ") " <> body <> ")") `shouldBe` Right (Abs [ident] (Sym body))
+
+  prop "parses a lambda-expression with multiple bindings as an abstraction" $ \(NonEmpty idents) (Identifier body) ->
+    let vars = unIdent <$> idents
+        nestedAbs = Abs vars (Sym body)
+     in parse ("(lam (" <> Text.unwords vars <> ") " <> body <> ")") `shouldBe` Right nestedAbs
 
-newtype Identifier = Identifier Text
+newtype Identifier = Identifier {unIdent :: Text}
   deriving (Eq, Show)
 
 instance Arbitrary Identifier where