tidy up

README.md

@@ -1 +1,5 @@
 # crafting-interpreters-hs
+
+Usage: `lox [file]`
+
+Implemented up to control flow statements (chapter 9).

app/Main.hs

@@ -15,8 +15,20 @@ run source = do
                 Left (SyntaxError s) -> putStrLn s
                 Right statements -> runStatements statements
 
+runEval :: String -> IO ()
+runEval source = do 
+    let tokensMaybe = scanTokensFromSource source
+    object <- case tokensMaybe of
+        Left UnexpectedCharacterError -> putStrLn "Unexpected character" >> return NullObject
+        Right tokens -> do
+            let exprMaybe = parseExpression tokens
+            case exprMaybe of
+                Left (SyntaxError s) -> putStrLn s >> return NullObject
+                Right statements -> eval statements
+    print object
+
 repl :: IO ()
-repl = putStr ">> " >> hFlush stdout >> getLine >>= run 
+repl = putStr ">> " >> hFlush stdout >> getLine >>= runEval
 
 main :: IO ()
 main = getArgs >>= fs

examples/fibonacci.lox

@@ -0,0 +1,9 @@
+var a = 0;
+var temp;
+
+for (var b = 1; a < 10000; b = temp + b) {
+  print a;
+  temp = a;
+  a = b;
+}
+

examples/scope.lox

@@ -0,0 +1,19 @@
+var a = "global a";
+var b = "global b";
+var c = "global c";
+{
+  var a = "outer a";
+  var b = "outer b";
+  {
+    var a = "inner a";
+    print a;
+    print b;
+    print c;
+  }
+  print a;
+  print b;
+  print c;
+}
+print a;
+print b;
+print c;

src/Lox/Parser.hs

@@ -1,6 +1,7 @@
 module Lox.Parser (
     SyntaxError (..),
-    parse
+    parse,
+    parseExpression
 ) where
 
 import Control.Monad
@@ -55,6 +56,9 @@ data SyntaxError = SyntaxError String deriving Show
 parse :: [Token] -> Either SyntaxError [Stmt]
 parse tokens = evalState program (ParserState {tokens=tokens})
 
+parseExpression :: [Token] -> Either SyntaxError Expr
+parseExpression tokens = evalState expression (ParserState {tokens=tokens})
+
 program :: State ParserState (Either SyntaxError [Stmt])
 program = do
     atEnd <- isAtEnd