Statement parsing

3 files changed, 32 insertions, 9 deletions

diff --git a/src/SPL/Lex.hs b/src/SPL/Lex.hs
index 21b8a82..b8f09e3 100644
--- a/src/SPL/Lex.hs
+++ b/src/SPL/Lex.hs
@@ -30,6 +30,7 @@ data Token
   | TArrow
 
   | TIf
+  | TElse
   | TWhile
   | TReturn
   | TVar
@@ -107,6 +108,7 @@ lex s = (comment s <|> item s <|> int s <|> char s <|> bool s <|> ident s) >>=
 
     item :: (Alternative m) => String -> m (Token, String)
     item ('i':'f':s) = noIdentifier TIf s
+    item ('e':'l':'s':'e':s) = noIdentifier TElse s
     item ('w':'h':'i':'l':'e':s) = noIdentifier TWhile s
     item ('r':'e':'t':'u':'r':'n':s) = noIdentifier TReturn s
     item ('v':'a':'r':s) = noIdentifier TVar s
diff --git a/src/SPL/Parse.hs b/src/SPL/Parse.hs
index c05b755..4331ccb 100644
--- a/src/SPL/Parse.hs
+++ b/src/SPL/Parse.hs
@@ -3,12 +3,13 @@
 module SPL.Parse (parse)
 where
 
-import Text.Parsec (sepBy)
-import qualified Text.Parsec as P
-
 import Control.Applicative
+import Control.Monad
 import Data.Functor
 
+import Text.Parsec (sepBy, (<?>))
+import qualified Text.Parsec as P
+
 import SPL.Syntax hiding (TInt,TBool,TChar,TArrow)
 import qualified SPL.Syntax
 import SPL.Lex
@@ -22,7 +23,7 @@ satisfy p = P.tokenPrim
   (\t -> if p t then Just t else Nothing)
 
 token :: Token -> Parser Token
-token = satisfy . (==)
+token t = satisfy (== t) <?> show t
 
 check :: (Token -> Maybe a) -> Parser a
 check f = P.tokenPrim
@@ -48,6 +49,12 @@ comment = toString <$> satisfy isCommentToken
     toString (TSingleComment s) = s
     toString (TBlockComment s)  = s
 
+parenthesised :: Parser a -> Parser a
+parenthesised p = token TParenOpen *> p <* token TParenClose
+
+braced :: Parser a -> Parser a
+braced p = token TBraceOpen *> p <* token TBraceClose
+
 var :: Parser Variable
 var = do
   t  <- Just <$> plainType <|> (token TVar $> Nothing)
@@ -60,13 +67,11 @@ var = do
 fun :: Parser Function
 fun = do
   id <- ident
-  token TParenOpen
-  args <- ident `sepBy` token TComma
-  token TParenClose
+  args <- parenthesised $ ident `sepBy` token TComma
   ftype <- optional (token TColonColon *> funType)
   token TBraceOpen
   vars <- many var
-  stmt <- statement
+  stmt <- statements
   token TBraceClose
   return $ Function id ftype args vars stmt
 
@@ -95,5 +100,20 @@ expr = literal -- TODO
       TBool b -> Just (LBool b)
       _       -> Nothing
 
+statements :: Parser Statement
+statements = foldr1 Seq <$> some statement <|> pure Nop
+
 statement :: Parser Statement
-statement = fail "" -- TODO
+statement =
+  liftM3 If
+    (token TIf *> parenthesised expr)
+    (braced statements)
+    (optional (token TElse *> braced statements)) <|>
+  liftM2 While
+    (token TWhile *> parenthesised expr)
+    (braced statements) <|>
+  liftM2 Assign
+    ident
+    (token TEquals *> expr <* token TSemicolon) <|>
+  Eval <$> (expr <* token TSemicolon) <|>
+  Return <$> (token TReturn *> optional expr <* token TSemicolon)
diff --git a/src/SPL/Syntax.hs b/src/SPL/Syntax.hs
index d274803..e40d47c 100644
--- a/src/SPL/Syntax.hs
+++ b/src/SPL/Syntax.hs
@@ -42,6 +42,7 @@ data Statement
   | Eval Expression
   | Return (Maybe Expression)
   | Seq Statement Statement
+  | Nop
   deriving (Show)
 
 data Expression