Tests and better default REPL behavior

src/Main.hs

@@ -10,7 +10,18 @@ import qualified Data.Map as Map
 import Text.Megaparsec (runParser)
 
 main :: IO ()
-main = repl Map.empty --(Map.fromList [("__result", Leaf)])
+main = repl library
 
 runSapling :: String -> String
 runSapling s = show $ result (evalSapling Map.empty $ parseSapling s)
+
+library = evalSapling Map.empty $ parseSapling
+      "false = t\n \ 
+     \ true = t t\n \
+     \ id = (\\a : a)\n \
+     \ triage = (\\a b c : t (t a b) c)\n \
+     \ match_bool = (\\ot of : triage of (\\z : ot) t)\n \
+     \ and = match_bool id (\\z : false)\n \
+     \ if = (\\cond then else : t (t else (t t then)) t cond)"
+
+runSaplingEnv env s = show $ result (evalSapling env $ parseSapling s)

src/Parser.hs

@@ -32,7 +32,6 @@ parseSapling input =
   in map parseSingle nonEmptyLines
 
 parseSingle :: String -> SaplingAST
-parseSingle "" = error "Empty input provided to parseSingle"
 parseSingle input = case runParser parseExpression "" (lexSapling input) of
   Left err -> error $ handleParseError err
   Right ast -> ast

src/REPL.hs

@@ -16,6 +16,10 @@ repl env = do
   input <- getLine
   if input == "_:exit"
     then putStrLn "Goodbye!"
+  else if input == ""
+    then do 
+      putStrLn ""
+      repl env
     else do
       let clearEnv = Map.delete "__result" env
       let newEnv   = evalSingle clearEnv (parseSingle input)