🎃 Function application

a3/a3-handout/.gitignore

@@ -0,0 +1 @@
+dist-newstyle

a3/a3-handout/src/APL/Parser.hs

@@ -75,6 +75,17 @@ pAtom =
       lString "(" *> pExp <* lString ")"
     ]
 
+pFExp :: Parser Exp
+pFExp = pAtom >>= chain
+  where
+    chain x =
+      choice
+        [ do
+            y <- pAtom
+            chain $ Apply x y,
+          pure x
+        ]
+
 pLExp :: Parser Exp
 pLExp =
   choice
@@ -82,7 +93,7 @@ pLExp =
         <$> (lKeyword "if" *> pExp)
         <*> (lKeyword "then" *> pExp)
         <*> (lKeyword "else" *> pExp),
-      pAtom
+      pFExp
     ]
 
 pExp1 :: Parser Exp

a3/a3-handout/src/APL/Parser_Tests.hs

@@ -64,5 +64,11 @@ tests =
         "Lexing edge cases"
         [ parserTest "2 " $ CstInt 2,
           parserTest " 2" $ CstInt 2
+        ],
+      testGroup
+        "FExp"
+        [ parserTest "x y" $ Apply (Var "x") (Var "y"),
+          parserTest "x y z" $ Apply (Apply (Var "x") (Var "y")) (Var "z"),
+          parserTest "x (y z)" $ Apply (Var "x") (Apply (Var "y") (Var "z"))
         ]
     ]